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2527 discussions

Re: [PATCH v2 RESEND 2/3] i2c: qcom_geni: Update compile dependenices for qcom geni

by Bjorn Andersson

On Mon, Nov 11, 2024 at 07:32:43PM +0530, Jyothi Kumar Seerapu wrote: > I2C_QCOM_GENI is having compile dependencies on QCOM_GPI_DMA and > so update I2C_QCOM_GENI to depends on QCOM_GPI_DMA. > Given that this is a separate patch, your wording can only be interpreted as this being an existing problem. > Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu(a)quicinc.com> > --- > > v1 -> v2: > This patch is added in v2 to address the kernel test robot > reported compilation error. > ERROR: modpost: "gpi_multi_desc_process" [drivers/i2c/busses/i2c-qcom-geni.ko] undefined! But as far as I can tell you introduce this problem in patch 3. If so this addition should be part of patch 3. Also, you have different subject prefix for patch 2 and 3, yet they relate to the same driver. Not pretty. Regards, Bjorn > > drivers/i2c/busses/Kconfig | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig > index 0aa948014008..87634a682855 100644 > --- a/drivers/i2c/busses/Kconfig > +++ b/drivers/i2c/busses/Kconfig > @@ -1049,6 +1049,7 @@ config I2C_QCOM_GENI > tristate "Qualcomm Technologies Inc.'s GENI based I2C controller" > depends on ARCH_QCOM || COMPILE_TEST > depends on QCOM_GENI_SE > + depends on QCOM_GPI_DMA > help > This driver supports GENI serial engine based I2C controller in > master mode on the Qualcomm Technologies Inc.'s SoCs. If you say > -- > 2.17.1 > >

1 month, 1 week

Re: [PATCH 2/3] dma-buf: sort fences in dma_fence_unwrap_merge

by Christian König

Am 08.11.24 um 12:22 schrieb Tvrtko Ursulin: > On 07/11/2024 16:00, Tvrtko Ursulin wrote: >> On 24/10/2024 13:41, Christian König wrote: >>> The merge function initially handled only individual fences and >>> arrays which in turn were created by the merge function. This allowed >>> to create the new array by a simple merge sort based on the fence >>> context number. >>> >>> The problem is now that since the addition of timeline sync objects >>> userspace can create chain containers in basically any fence context >>> order. >>> >>> If those are merged together it can happen that we create really >>> large arrays since the merge sort algorithm doesn't work any more. >>> >>> So put an insert sort behind the merge sort which kicks in when the >>> input fences are not in the expected order. This isn't as efficient >>> as a heap sort, but has better properties for the most common use >>> case. >>> >>> Signed-off-by: Christian König <christian.koenig(a)amd.com> >>> --- >>> drivers/dma-buf/dma-fence-unwrap.c | 39 >>> ++++++++++++++++++++++++++---- >>> 1 file changed, 34 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/dma-buf/dma-fence-unwrap.c >>> b/drivers/dma-buf/dma-fence-unwrap.c >>> index 628af51c81af..d9aa280d9ff6 100644 >>> --- a/drivers/dma-buf/dma-fence-unwrap.c >>> +++ b/drivers/dma-buf/dma-fence-unwrap.c >>> @@ -106,7 +106,7 @@ struct dma_fence >>> *__dma_fence_unwrap_merge(unsigned int num_fences, >>> fences[i] = dma_fence_unwrap_first(fences[i], &iter[i]); >>> count = 0; >>> - do { >>> + while (true) { >>> unsigned int sel; >>> restart: >>> @@ -144,11 +144,40 @@ struct dma_fence >>> *__dma_fence_unwrap_merge(unsigned int num_fences, >>> } >>> } >>> - if (tmp) { >>> - array[count++] = dma_fence_get(tmp); >>> - fences[sel] = dma_fence_unwrap_next(&iter[sel]); >>> + if (!tmp) >>> + break; >>> + >>> + /* >>> + * We could use a binary search here, but since the assumption >>> + * is that the main input are already sorted dma_fence_arrays >>> + * just looking from end has a higher chance of finding the >>> + * right location on the first try >>> + */ >>> + >>> + for (i = count; i--;) { >>> + if (likely(array[i]->context < tmp->context)) >>> + break; >>> + >>> + if (array[i]->context == tmp->context) { >>> + if (dma_fence_is_later(tmp, array[i])) { >>> + dma_fence_put(array[i]); >>> + array[i] = dma_fence_get(tmp); >>> + } >>> + fences[sel] = dma_fence_unwrap_next(&iter[sel]); >>> + goto restart; >>> + } >>> } >>> - } while (tmp); >>> + >>> + ++i; >>> + /* >>> + * Make room for the fence, this should be a nop most of the >>> + * time. >>> + */ >>> + memcpy(&array[i + 1], &array[i], (count - i) * >>> sizeof(*array)); >>> + array[i] = dma_fence_get(tmp); >>> + fences[sel] = dma_fence_unwrap_next(&iter[sel]); >>> + count++; >> >> Having ventured into this function for the first time, I can say that >> this is some smart code which is not easy to grasp. It could >> definitely benefit from a high level comment before the do-while loop >> to explain what it is going to do. >> >> Next and tmp local variable names I also wonder if could be renamed >> to something more descriptive. >> >> And the algorithmic complexity of the end result, given the multiple >> loops and gotos, I have no idea what it could be. >> >> Has a dumb solution been considered like a two-pass with a >> pessimistically allocated fence array been considered? Like: >> >> 1) Populate array with all unsignalled unwrapped fences. (O(count)) >> >> 2) Bog standard include/linux/sort.h by context and seqno. >> (O(count*log (count))) >> >> 3) Walk array and squash same context to latest fence. (Before this >> patch that wasn't there, right?). (O(count)) (Overwrite in place, no >> memcpy needed.) >> >> Algorithmic complexity of that would be obvious and code much simpler. > > FWIW something like the below passes selftests. How does it look to > you? Do you think more or less efficient and more or less readable? Yeah I was considering the exact same thing. What hold me back was the fact that the heap sort() implementation is really inefficient for the most common use case of this. In other words two arrays with fences already sorted is basically just O(count). And I'm also not sure how many fences we see in those arrays in practice. With Vulkan basically trying to feed multiple contexts to keep all CPUs busy we might have quite a number here. Regards, Christian. > > commit 8a7c3ea7e7af85e813bf5fc151537ae37be1d6d9 > Author: Tvrtko Ursulin <tvrtko.ursulin(a)igalia.com> > Date: Fri Nov 8 10:14:15 2024 +0000 > > __dma_fence_unwrap_merge > > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin(a)igalia.com> > > diff --git a/drivers/dma-buf/dma-fence-unwrap.c > b/drivers/dma-buf/dma-fence-unwrap.c > index 628af51c81af..47d67e482e96 100644 > --- a/drivers/dma-buf/dma-fence-unwrap.c > +++ b/drivers/dma-buf/dma-fence-unwrap.c > @@ -12,6 +12,7 @@ > #include <linux/dma-fence-chain.h> > #include <linux/dma-fence-unwrap.h> > #include <linux/slab.h> > +#include <linux/sort.h> > > /* Internal helper to start new array iteration, don't use directly */ > static struct dma_fence * > @@ -59,17 +60,39 @@ struct dma_fence *dma_fence_unwrap_next(struct > dma_fence_unwrap *cursor) > } > EXPORT_SYMBOL_GPL(dma_fence_unwrap_next); > > + > +static int fence_cmp(const void *_a, const void *_b) > +{ > + const struct dma_fence *a = *(const struct dma_fence **)_a; > + const struct dma_fence *b = *(const struct dma_fence **)_b; > + > + if (a->context < b->context) > + return -1; > + else if (a->context > b->context) > + return 1; > + > + if (a->seqno < b->seqno) > + return -1; > + else if (a->seqno > b->seqno) > + return 1; > + > + return 0; > +} > + > /* Implementation for the dma_fence_merge() marco, don't use directly */ > struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences, > struct dma_fence **fences, > struct dma_fence_unwrap *iter) > { > - struct dma_fence_array *result; > struct dma_fence *tmp, **array; > + struct dma_fence_array *result; > ktime_t timestamp; > - unsigned int i; > - size_t count; > + int i, j, count; > > + /* > + * Count number of unwrapped fences and fince the latest signaled > + * timestamp. > + */ > count = 0; > timestamp = ns_to_ktime(0); > for (i = 0; i < num_fences; ++i) { > @@ -92,63 +115,41 @@ struct dma_fence > *__dma_fence_unwrap_merge(unsigned int num_fences, > if (count == 0) > return dma_fence_allocate_private_stub(timestamp); > > + /* > + * Allocate and populate the array. > + */ > array = kmalloc_array(count, sizeof(*array), GFP_KERNEL); > if (!array) > return NULL; > > - /* > - * This trashes the input fence array and uses it as position for > the > - * following merge loop. This works because the dma_fence_merge() > - * wrapper macro is creating this temporary array on the stack > together > - * with the iterators. > - */ > - for (i = 0; i < num_fences; ++i) > - fences[i] = dma_fence_unwrap_first(fences[i], &iter[i]); > - > count = 0; > - do { > - unsigned int sel; > - > -restart: > - tmp = NULL; > - for (i = 0; i < num_fences; ++i) { > - struct dma_fence *next; > - > - while (fences[i] && dma_fence_is_signaled(fences[i])) > - fences[i] = dma_fence_unwrap_next(&iter[i]); > - > - next = fences[i]; > - if (!next) > - continue; > - > - /* > - * We can't guarantee that inpute fences are ordered by > - * context, but it is still quite likely when this > - * function is used multiple times. So attempt to order > - * the fences by context as we pass over them and merge > - * fences with the same context. > - */ > - if (!tmp || tmp->context > next->context) { > - tmp = next; > - sel = i; > - > - } else if (tmp->context < next->context) { > - continue; > - > - } else if (dma_fence_is_later(tmp, next)) { > - fences[i] = dma_fence_unwrap_next(&iter[i]); > - goto restart; > - } else { > - fences[sel] = dma_fence_unwrap_next(&iter[sel]); > - goto restart; > - } > + for (i = 0; i < num_fences; ++i) { > + dma_fence_unwrap_for_each(tmp, &iter[i], fences[i]) { > + if (!dma_fence_is_signaled(tmp)) > + array[count++] = tmp; > } > + } > + > + /* > + * Sort in context and seqno order. > + */ > + sort(array, count, sizeof(*array), fence_cmp, NULL); > > - if (tmp) { > - array[count++] = dma_fence_get(tmp); > - fences[sel] = dma_fence_unwrap_next(&iter[sel]); > + /* > + * Only keep the most recent fence for each context. > + */ > + j = 0; > + tmp = array[0]; > + for (i = 1; i < count; i++) { > + if (array[i]->context != tmp->context) { > + array[j++] = dma_fence_get(tmp); > } > - } while (tmp); > + tmp = array[i]; > + } > + if (tmp->context != array[j - 1]->context) { > + array[j++] = dma_fence_get(tmp); > + } > + count = j; > > if (count == 0) { > tmp = dma_fence_allocate_private_stub(ktime_get()); > > > Regards, > > Tvrtko > > >> >> Regards, >> >> Tvrtko >> >>> + }; >>> if (count == 0) { >>> tmp = dma_fence_allocate_private_stub(ktime_get());

1 month, 1 week

Re: [PATCH 1/3] dma-buf/dma-fence_array: use kvzalloc

by Christian König

Am 07.11.24 um 12:29 schrieb Tvrtko Ursulin: > > On 28/10/2024 10:34, Christian König wrote: >> Am 25.10.24 um 11:05 schrieb Tvrtko Ursulin: >>> >>> On 25/10/2024 09:59, Tvrtko Ursulin wrote: >>>> >>>> On 24/10/2024 13:41, Christian König wrote: >>>>> Reports indicates that some userspace applications try to merge >>>>> more than >>>>> 80k of fences into a single dma_fence_array leading to a warning from >>>>> kzalloc() that the requested size becomes to big. >>>>> >>>>> While that is clearly an userspace bug we should probably handle >>>>> that case >>>>> gracefully in the kernel. >>>>> >>>>> So we can either reject requests to merge more than a reasonable >>>>> amount of >>>>> fences (64k maybe?) or we can start to use kvzalloc() instead of >>>>> kzalloc(). >>>>> This patch here does the later. >>>> >>>> Rejecting would potentially be safer, otherwise there is a path for >>>> userspace to trigger a warn in kvmalloc_node (see 0829b5bcdd3b >>>> ("drm/i915: 2 GiB of relocations ought to be enough for anybody*")) >>>> and spam dmesg at will. >>> >>> Actually that is a WARN_ON_*ONCE* there so maybe not so critical to >>> invent a limit. Up for discussion I suppose. >>> >>> Regards, >>> >>> Tvrtko >>> >>>> >>>> Question is what limit to set... >> >> That's one of the reasons why I opted for kvzalloc() initially. > > I didn't get that, what was the reason? To not have to invent an > arbitrary limit? Well that I couldn't come up with any arbitrary limit that I had confidence would work and not block real world use cases. Switching to kvzalloc() just seemed the more defensive approach. > >> I mean we could use some nice round number like 65536, but that would >> be totally arbitrary. > > Yeah.. Set an arbitrary limit so a warning in __kvmalloc_node_noprof() > is avoided? Or pass __GFP_NOWARN? Well are we sure that will never hit 65536 in a real world use case? It's still pretty low. > >> Any comments on the other two patches? I need to get them upstream. > > Will look into them shortly. Thanks, Christian. > > Regards, > > Tvrtko > > >> Thanks, >> Christian. >> >>>> >>>> Regards, >>>> >>>> Tvrtko >>>> >>>>> Signed-off-by: Christian König <christian.koenig(a)amd.com> >>>>> CC: stable(a)vger.kernel.org >>>>> --- >>>>> drivers/dma-buf/dma-fence-array.c | 6 +++--- >>>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>>> >>>>> diff --git a/drivers/dma-buf/dma-fence-array.c >>>>> b/drivers/dma-buf/dma-fence-array.c >>>>> index 8a08ffde31e7..46ac42bcfac0 100644 >>>>> --- a/drivers/dma-buf/dma-fence-array.c >>>>> +++ b/drivers/dma-buf/dma-fence-array.c >>>>> @@ -119,8 +119,8 @@ static void dma_fence_array_release(struct >>>>> dma_fence *fence) >>>>> for (i = 0; i < array->num_fences; ++i) >>>>> dma_fence_put(array->fences[i]); >>>>> - kfree(array->fences); >>>>> - dma_fence_free(fence); >>>>> + kvfree(array->fences); >>>>> + kvfree_rcu(fence, rcu); >>>>> } >>>>> static void dma_fence_array_set_deadline(struct dma_fence *fence, >>>>> @@ -153,7 +153,7 @@ struct dma_fence_array >>>>> *dma_fence_array_alloc(int num_fences) >>>>> { >>>>> struct dma_fence_array *array; >>>>> - return kzalloc(struct_size(array, callbacks, num_fences), >>>>> GFP_KERNEL); >>>>> + return kvzalloc(struct_size(array, callbacks, num_fences), >>>>> GFP_KERNEL); >>>>> } >>>>> EXPORT_SYMBOL(dma_fence_array_alloc); >>

1 month, 2 weeks

Re: [PATCH 2/3] dma-buf: sort fences in dma_fence_unwrap_merge

by Christian König

Am 30.10.24 um 19:10 schrieb Friedrich Vock: > On 24.10.24 14:41, Christian König wrote: >> The merge function initially handled only individual fences and >> arrays which in turn were created by the merge function. This allowed >> to create the new array by a simple merge sort based on the fence >> context number. >> >> The problem is now that since the addition of timeline sync objects >> userspace can create chain containers in basically any fence context >> order. >> >> If those are merged together it can happen that we create really >> large arrays since the merge sort algorithm doesn't work any more. >> >> So put an insert sort behind the merge sort which kicks in when the >> input fences are not in the expected order. This isn't as efficient >> as a heap sort, but has better properties for the most common use >> case. >> >> Signed-off-by: Christian König <christian.koenig(a)amd.com> >> --- >> drivers/dma-buf/dma-fence-unwrap.c | 39 ++++++++++++++++++++++++++---- >> 1 file changed, 34 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/dma-buf/dma-fence-unwrap.c >> b/drivers/dma-buf/dma-fence-unwrap.c >> index 628af51c81af..d9aa280d9ff6 100644 >> --- a/drivers/dma-buf/dma-fence-unwrap.c >> +++ b/drivers/dma-buf/dma-fence-unwrap.c >> @@ -106,7 +106,7 @@ struct dma_fence >> *__dma_fence_unwrap_merge(unsigned int num_fences, >> fences[i] = dma_fence_unwrap_first(fences[i], &iter[i]); >> >> count = 0; >> - do { >> + while (true) { >> unsigned int sel; >> >> restart: >> @@ -144,11 +144,40 @@ struct dma_fence >> *__dma_fence_unwrap_merge(unsigned int num_fences, >> } >> } >> >> - if (tmp) { >> - array[count++] = dma_fence_get(tmp); >> - fences[sel] = dma_fence_unwrap_next(&iter[sel]); >> + if (!tmp) >> + break; >> + >> + /* >> + * We could use a binary search here, but since the assumption >> + * is that the main input are already sorted dma_fence_arrays >> + * just looking from end has a higher chance of finding the >> + * right location on the first try >> + */ >> + >> + for (i = count; i--;) { > > This is broken. The first iteration of this loop will always index out > of bounds. Nope, that is correct. The condition is evaluated before the loop, so the i-- reduces the index to the last element in the array. Regards, Christian. > What you probably want here is: > > + for (i = count - 1; count && i--;) { > > This intentionally overflows for count == 0, but the ++i after the loop > undoes that. Maybe it would be worth a comment to point out that's > intentional. > >> + if (likely(array[i]->context < tmp->context)) >> + break; >> + >> + if (array[i]->context == tmp->context) { >> + if (dma_fence_is_later(tmp, array[i])) { >> + dma_fence_put(array[i]); >> + array[i] = dma_fence_get(tmp); >> + } >> + fences[sel] = dma_fence_unwrap_next(&iter[sel]); >> + goto restart; >> + } >> } >> - } while (tmp); >> + >> + ++i; >> + /* >> + * Make room for the fence, this should be a nop most of the >> + * time. >> + */ >> + memcpy(&array[i + 1], &array[i], (count - i) * sizeof(*array)); > > Need memmove here, src and dst alias. > > I took it for a spin with these things fixed and it seemed to resolve > the issue as well. How do you want to proceed? I guess I would be > comfortable putting a Reviewed-by and/or Tested-by on a version with > these things fixed (with the usual caveat that I'm not a maintainer - I > guess the process requires (at least one) reviewer to be?). > > By the way, I guess you might've had some internal branches where this > fix needed to go into quick or something? Usually I'm happy to make a v2 > for my patches myself, too ;) > > Regards, > Friedrich > >> + array[i] = dma_fence_get(tmp); >> + fences[sel] = dma_fence_unwrap_next(&iter[sel]); >> + count++; >> + }; >> >> if (count == 0) { >> tmp = dma_fence_allocate_private_stub(ktime_get()); >

1 month, 2 weeks

Re: Requirements to merge new heaps in the kernel

by Al Viro

On Thu, Oct 31, 2024 at 05:45:23PM +0100, Maxime Ripard wrote: > On Wed, Oct 30, 2024 at 12:16:22PM +0100, metux wrote: > > On 22.10.24 10:38, Maxime Ripard wrote: > > > I'm still interested in merging a carve-out driver[1], since it seems to be > > > in every vendor BSP and got asked again last week. > > > > > > I remember from our discussion that for new heap types to be merged, we > > > needed a kernel use-case. Looking back, I'm not entirely sure how one > > > can provide that given that heaps are essentially facilities for > > > user-space. > > > > For those who didn't follow your work, could you please give a short > > intro what's that all about ? > > > > If I understand you correctly, you'd like the infrastructure of > > kmalloc() et al for things / memory regions that aren't the usual heap, > > right ? > > No, not really. The discussion is about dma-buf heaps. They allow to > allocate buffers suitable for DMA from userspace. It might or might not > from the system memory, at the heap driver discretion. I'm afraid you've misinterpreted that - our hexapedal friend had just * noticed that excessive crossposting can get it banned * got itself a new address * posted a solitary ping as the first test * followed that by testing the ability to cross-post (posting you'd been replying to, contents on chatGPT level) * proceeded to use its shiny new address for more of the chorus whinge exercise they'd been holding with several other similar fellows (or sock puppets, for all I know). Just ignore the wanker - it wasn't trying to get any information other than "will the posting get through" anyway.

1 month, 3 weeks

Re: [PATCH v6 02/15] net: generalise net_iov chunk owners

by Christoph Hellwig

On Tue, Oct 29, 2024 at 04:35:16PM +0000, Pavel Begunkov wrote: > I see, the reply is about your phrase about additional memory > abstractions: > > "... don't really need to build memory buffer abstraction over > memory buffer abstraction." Yes, over the exsting memory buffer abstraction (dma_buf). > If you mean internals, making up a dmabuf that has never existed in the > picture in the first place is not cleaner or easier in any way. If that > changes, e.g. there is more code to reuse in the future, we can unify it > then. I'm not sure what "making up" means here, they are all made up :) > > with pre-registering the memry with the iommu to get good performance > > in IOMMU-enabled setups. > > The page pool already does that just like it handles the normal > path without providers. In which case is basically is a dma-buf. If you'd expose it as such we could actually use to communicate between subsystems in the kernel.

1 month, 3 weeks

Re: [PATCH 1/3] dma-buf/dma-fence_array: use kvzalloc

by Christian König

Am 25.10.24 um 08:52 schrieb Friedrich Vock: > On 24.10.24 22:29, Matthew Brost wrote: >> On Thu, Oct 24, 2024 at 02:41:57PM +0200, Christian König wrote: >>> Reports indicates that some userspace applications try to merge more >>> than >>> 80k of fences into a single dma_fence_array leading to a warning from >> >> Really, yikes. > > Not really IME. Unless Christian means some reports I don't have access > to, the cases where userspace applications tried to do that were really > just cases where the fence count exploded exponentially because > dma_fence_unwrap_merge failed to actually merge identical fences (see > patch 2). At no point have I actually seen apps trying to merge 80k+ > unique fences. While working on it I've modified our stress test tool to send the same 1GiB SDMA copy to 100k different contexts. Turned out it's perfectly possible to create so many fences, there is nothing blocking userspace to do it. While this isn't a realistic use case the kernel should at least not crash or spill a warning, but either handle or reject it gracefully. Friedrich can you confirm that patch two in this series fixes the problem? I would really like to get it into drm-misc-fixes before 6.12 comes out. Thanks, Christian. > > Regards, > Friedrich > >> >>> kzalloc() that the requested size becomes to big. >>> >>> While that is clearly an userspace bug we should probably handle >>> that case >>> gracefully in the kernel. >>> >>> So we can either reject requests to merge more than a reasonable >>> amount of >>> fences (64k maybe?) or we can start to use kvzalloc() instead of >>> kzalloc(). >>> This patch here does the later. >>> >> >> This patch seems reasonable to me if the above use is in fact valid. >> >>> Signed-off-by: Christian König <christian.koenig(a)amd.com> >>> CC: stable(a)vger.kernel.org >> >> Fixes tag? >> >> Patch itself LGTM: >> Reviewed-by: Matthew Brost <matthew.brost(a)intel.com> >> >>> --- >>> drivers/dma-buf/dma-fence-array.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/dma-buf/dma-fence-array.c >>> b/drivers/dma-buf/dma-fence-array.c >>> index 8a08ffde31e7..46ac42bcfac0 100644 >>> --- a/drivers/dma-buf/dma-fence-array.c >>> +++ b/drivers/dma-buf/dma-fence-array.c >>> @@ -119,8 +119,8 @@ static void dma_fence_array_release(struct >>> dma_fence *fence) >>> for (i = 0; i < array->num_fences; ++i) >>> dma_fence_put(array->fences[i]); >>> >>> - kfree(array->fences); >>> - dma_fence_free(fence); >>> + kvfree(array->fences); >>> + kvfree_rcu(fence, rcu); >>> } >>> >>> static void dma_fence_array_set_deadline(struct dma_fence *fence, >>> @@ -153,7 +153,7 @@ struct dma_fence_array >>> *dma_fence_array_alloc(int num_fences) >>> { >>> struct dma_fence_array *array; >>> >>> - return kzalloc(struct_size(array, callbacks, num_fences), >>> GFP_KERNEL); >>> + return kvzalloc(struct_size(array, callbacks, num_fences), >>> GFP_KERNEL); >>> } >>> EXPORT_SYMBOL(dma_fence_array_alloc); >>> >>> -- >>> 2.34.1 >>> >

1 month, 3 weeks

Re: [PATCH v6 02/15] net: generalise net_iov chunk owners

by Christoph Hellwig

On Thu, Oct 24, 2024 at 05:40:02PM +0100, Pavel Begunkov wrote: > On 10/24/24 17:06, Christoph Hellwig wrote: > > On Thu, Oct 24, 2024 at 03:23:06PM +0100, Pavel Begunkov wrote: > > > > That's not what this series does. It adds the new memory_provider_ops > > > > set of hooks, with once implementation for dmabufs, and one for > > > > io_uring zero copy. > > > > > > First, it's not a _new_ abstraction over a buffer as you called it > > > before, the abstraction (net_iov) is already merged. > > > > Umm, it is a new ops vector. > > I don't understand what you mean. Callback? struct memory_provider_ops. It's a method table or ops vetor, no callbacks involved. > Then please go ahead and take a look at the patchset in question > and see how much of dmabuf handling is there comparing to pure > networking changes. The point that it's a new set of API and lots > of changes not related directly to dmabufs stand. dmabufs is useful > there as an abstraction there, but it's a very long stretch saying > that the series is all about it. I did take a look, that's why I replied. > > > on an existing network specific abstraction, which are not restricted to > > > pages or anything specific in the long run, but the flow of which from > > > net stack to user and back is controlled by io_uring. If you worry about > > > abuse, io_uring can't even sanely initialise those buffers itself and > > > therefore asking the page pool code to do that. > > > > No, I worry about trying to io_uring for not good reason. This > > It sounds that the argument is that you just don't want any > io_uring APIs, I don't think you'd be able to help you with > that. No, that's complete misinterpreting what I'm saying. Of course an io_uring API is fine. But tying low-level implementation details to to is not. > > pre-cludes in-kernel uses which would be extremly useful for > > Uses of what? devmem TCP is merged, I'm not removing it, > and the net_iov abstraction is in there, which can be potentially > be reused by other in-kernel users if that'd even make sense. How when you are hardcoding io uring memory registrations instead of making them a generic dmabuf? Which btw would also really help with pre-registering the memry with the iommu to get good performance in IOMMU-enabled setups.

1 month, 3 weeks

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Re: [PATCH 1/3] dma-buf/dma-fence_array: use kvzalloc

by Christian König

Am 25.10.24 um 11:05 schrieb Tvrtko Ursulin: > > On 25/10/2024 09:59, Tvrtko Ursulin wrote: >> >> On 24/10/2024 13:41, Christian König wrote: >>> Reports indicates that some userspace applications try to merge more >>> than >>> 80k of fences into a single dma_fence_array leading to a warning from >>> kzalloc() that the requested size becomes to big. >>> >>> While that is clearly an userspace bug we should probably handle >>> that case >>> gracefully in the kernel. >>> >>> So we can either reject requests to merge more than a reasonable >>> amount of >>> fences (64k maybe?) or we can start to use kvzalloc() instead of >>> kzalloc(). >>> This patch here does the later. >> >> Rejecting would potentially be safer, otherwise there is a path for >> userspace to trigger a warn in kvmalloc_node (see 0829b5bcdd3b >> ("drm/i915: 2 GiB of relocations ought to be enough for anybody*")) >> and spam dmesg at will. > > Actually that is a WARN_ON_*ONCE* there so maybe not so critical to > invent a limit. Up for discussion I suppose. > > Regards, > > Tvrtko > >> >> Question is what limit to set... That's one of the reasons why I opted for kvzalloc() initially. I mean we could use some nice round number like 65536, but that would be totally arbitrary. Any comments on the other two patches? I need to get them upstream. Thanks, Christian. >> >> Regards, >> >> Tvrtko >> >>> Signed-off-by: Christian König <christian.koenig(a)amd.com> >>> CC: stable(a)vger.kernel.org >>> --- >>> drivers/dma-buf/dma-fence-array.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/dma-buf/dma-fence-array.c >>> b/drivers/dma-buf/dma-fence-array.c >>> index 8a08ffde31e7..46ac42bcfac0 100644 >>> --- a/drivers/dma-buf/dma-fence-array.c >>> +++ b/drivers/dma-buf/dma-fence-array.c >>> @@ -119,8 +119,8 @@ static void dma_fence_array_release(struct >>> dma_fence *fence) >>> for (i = 0; i < array->num_fences; ++i) >>> dma_fence_put(array->fences[i]); >>> - kfree(array->fences); >>> - dma_fence_free(fence); >>> + kvfree(array->fences); >>> + kvfree_rcu(fence, rcu); >>> } >>> static void dma_fence_array_set_deadline(struct dma_fence *fence, >>> @@ -153,7 +153,7 @@ struct dma_fence_array >>> *dma_fence_array_alloc(int num_fences) >>> { >>> struct dma_fence_array *array; >>> - return kzalloc(struct_size(array, callbacks, num_fences), >>> GFP_KERNEL); >>> + return kvzalloc(struct_size(array, callbacks, num_fences), >>> GFP_KERNEL); >>> } >>> EXPORT_SYMBOL(dma_fence_array_alloc);

1 month, 3 weeks

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