This is a note to let you know that I've just added the patch titled
KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: kvm-ppc-book3s-hv-drop-prepare_done-from-struct-kvm_resize_hpt.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 3073774e638ef18d222465fe92bfc8fccb90d288 Mon Sep 17 00:00:00 2001
From: Serhii Popovych spopovyc@redhat.com Date: Mon, 4 Dec 2017 09:36:41 -0500 Subject: KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt
From: Serhii Popovych spopovyc@redhat.com
commit 3073774e638ef18d222465fe92bfc8fccb90d288 upstream.
Currently the kvm_resize_hpt structure has two fields relevant to the state of an ongoing resize: 'prepare_done', which indicates whether the worker thread has completed or not, and 'error' which indicates whether it was successful or not.
Since the success/failure isn't known until completion, this is confusingly redundant. This patch consolidates the information into just the 'error' value: -EBUSY indicates the worked is still in progress, other negative values indicate (completed) failure, 0 indicates successful completion.
As a bonus this reduces size of struct kvm_resize_hpt by __alignof__(struct kvm_hpt_info) and saves few bytes of code.
While there correct comment in struct kvm_resize_hpt which references a non-existent semaphore (leftover from an early draft).
Assert with WARN_ON() in case of HPT allocation thread work runs more than once for resize request or resize_hpt_allocate() returns -EBUSY that is treated specially.
Change comparison against zero to make checkpatch.pl happy.
Signed-off-by: Serhii Popovych spopovyc@redhat.com [dwg: Changed BUG_ON()s to WARN_ON()s and altered commit message for clarity] Signed-off-by: David Gibson david@gibson.dropbear.id.au Signed-off-by: Paul Mackerras paulus@ozlabs.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kvm/book3s_64_mmu_hv.c | 44 ++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 17 deletions(-)
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -65,11 +65,17 @@ struct kvm_resize_hpt { u32 order;
/* These fields protected by kvm->lock */ + + /* Possible values and their usage: + * <0 an error occurred during allocation, + * -EBUSY allocation is in the progress, + * 0 allocation made successfuly. + */ int error; - bool prepare_done;
- /* Private to the work thread, until prepare_done is true, - * then protected by kvm->resize_hpt_sem */ + /* Private to the work thread, until error != -EBUSY, + * then protected by kvm->lock. + */ struct kvm_hpt_info hpt; };
@@ -1444,15 +1450,23 @@ static void resize_hpt_prepare_work(stru struct kvm *kvm = resize->kvm; int err;
+ if (WARN_ON(resize->error != -EBUSY)) + return; + resize_hpt_debug(resize, "resize_hpt_prepare_work(): order = %d\n", resize->order);
err = resize_hpt_allocate(resize);
+ /* We have strict assumption about -EBUSY + * when preparing for HPT resize. + */ + if (WARN_ON(err == -EBUSY)) + err = -EINPROGRESS; + mutex_lock(&kvm->lock);
resize->error = err; - resize->prepare_done = true;
mutex_unlock(&kvm->lock); } @@ -1477,14 +1491,12 @@ long kvm_vm_ioctl_resize_hpt_prepare(str
if (resize) { if (resize->order == shift) { - /* Suitable resize in progress */ - if (resize->prepare_done) { - ret = resize->error; - if (ret != 0) - resize_hpt_release(kvm, resize); - } else { + /* Suitable resize in progress? */ + ret = resize->error; + if (ret == -EBUSY) ret = 100; /* estimated time in ms */ - } + else if (ret) + resize_hpt_release(kvm, resize);
goto out; } @@ -1504,6 +1516,8 @@ long kvm_vm_ioctl_resize_hpt_prepare(str ret = -ENOMEM; goto out; } + + resize->error = -EBUSY; resize->order = shift; resize->kvm = kvm; INIT_WORK(&resize->work, resize_hpt_prepare_work); @@ -1558,16 +1572,12 @@ long kvm_vm_ioctl_resize_hpt_commit(stru if (!resize || (resize->order != shift)) goto out;
- ret = -EBUSY; - if (!resize->prepare_done) - goto out; - ret = resize->error; - if (ret != 0) + if (ret) goto out;
ret = resize_hpt_rehash(resize); - if (ret != 0) + if (ret) goto out;
resize_hpt_pivot(resize);
Patches currently in stable-queue which might be from spopovyc@redhat.com are
queue-4.14/kvm-ppc-book3s-hv-drop-prepare_done-from-struct-kvm_resize_hpt.patch queue-4.14/kvm-ppc-book3s-hv-fix-use-after-free-in-case-of-multiple-resize-requests.patch