The patch titled
Subject: mm: do not drop unused pages when userfaultd is running
has been added to the -mm tree. Its filename is
mm-do-not-drop-unused-pages-when-userfaultd-is-running.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-do-not-drop-unused-pages-when-u…
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-do-not-drop-unused-pages-when-u…
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Christian Borntraeger <borntraeger(a)de.ibm.com>
Subject: mm: do not drop unused pages when userfaultd is running
KVM guests on s390 can notify the host of unused pages. This can result
in pte_unused callbacks to be true for KVM guest memory.
If a page is unused (checked with pte_unused) we might drop this page
instead of paging it. This can have side-effects on userfaultd, when the
page in question was already migrated:
The next access of that page will trigger a fault and a user fault instead
of faulting in a new and empty zero page. As QEMU does not expect a
userfault on an already migrated page this migration will fail.
The most straightforward solution is to ignore the pte_unused hint if a
userfault context is active for this VMA.
Link: http://lkml.kernel.org/r/20180703171854.63981-1-borntraeger@de.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger(a)de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky(a)de.ibm.com>
Cc: Andrea Arcangeli <aarcange(a)redhat.com>
Cc: Mike Rapoport <rppt(a)linux.vnet.ibm.com>
Cc: Janosch Frank <frankja(a)linux.ibm.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Cornelia Huck <cohuck(a)redhat.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/rmap.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff -puN mm/rmap.c~mm-do-not-drop-unused-pages-when-userfaultd-is-running mm/rmap.c
--- a/mm/rmap.c~mm-do-not-drop-unused-pages-when-userfaultd-is-running
+++ a/mm/rmap.c
@@ -64,6 +64,7 @@
#include <linux/backing-dev.h>
#include <linux/page_idle.h>
#include <linux/memremap.h>
+#include <linux/userfaultfd_k.h>
#include <asm/tlbflush.h>
@@ -1481,11 +1482,16 @@ static bool try_to_unmap_one(struct page
set_pte_at(mm, address, pvmw.pte, pteval);
}
- } else if (pte_unused(pteval)) {
+ } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
/*
* The guest indicated that the page content is of no
* interest anymore. Simply discard the pte, vmscan
* will take care of the rest.
+ * A future reference will then fault in a new zero
+ * page. When userfaultfd is active, we must not drop
+ * this page though, as its main user (postcopy
+ * migration) will not expect userfaults on already
+ * copied pages.
*/
dec_mm_counter(mm, mm_counter(page));
/* We have to invalidate as we cleared the pte */
_
Patches currently in -mm which might be from borntraeger(a)de.ibm.com are
mm-do-not-drop-unused-pages-when-userfaultd-is-running.patch
Tree/Branch: v4.4.139
Git describe: v4.4.139
Commit: 16af098616 Linux 4.4.139
Build Time: 63 min 11 sec
Passed: 10 / 10 (100.00 %)
Failed: 0 / 10 ( 0.00 %)
Errors: 0
Warnings: 31
Section Mismatches: 0
-------------------------------------------------------------------------------
defconfigs with issues (other than build errors):
19 warnings 0 mismatches : arm64-allmodconfig
17 warnings 0 mismatches : x86_64-allmodconfig
-------------------------------------------------------------------------------
Warnings Summary: 31
3 warning: (IMA) selects TCG_CRB which has unmet direct dependencies (TCG_TPM && X86 && ACPI)
2 ../drivers/media/dvb-frontends/stv090x.c:4250:1: warning: the frame size of 4832 bytes is larger than 2048 bytes [-Wframe-larger-than=]
2 ../drivers/media/dvb-frontends/stv090x.c:1211:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
2 ../drivers/media/dvb-frontends/stv090x.c:1168:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/net/ethernet/rocker/rocker.c:2172:1: warning: the frame size of 2752 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/net/ethernet/rocker/rocker.c:2172:1: warning: the frame size of 2720 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:4759:1: warning: the frame size of 2056 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:4565:1: warning: the frame size of 2096 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:4565:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:3436:1: warning: the frame size of 6784 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:3436:1: warning: the frame size of 5280 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:3095:1: warning: the frame size of 5864 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:3095:1: warning: the frame size of 5840 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:2513:1: warning: the frame size of 2304 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:2513:1: warning: the frame size of 2288 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:2141:1: warning: the frame size of 2104 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:2141:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:2073:1: warning: the frame size of 2552 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:2073:1: warning: the frame size of 2544 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:1956:1: warning: the frame size of 3264 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:1956:1: warning: the frame size of 3248 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:1858:1: warning: the frame size of 3008 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:1858:1: warning: the frame size of 2992 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:1599:1: warning: the frame size of 5296 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv090x.c:1599:1: warning: the frame size of 5280 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv0367.c:3147:1: warning: the frame size of 4144 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/stv0367.c:2490:1: warning: the frame size of 3424 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/cxd2841er.c:2401:1: warning: the frame size of 2984 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/cxd2841er.c:2401:1: warning: the frame size of 2976 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/cxd2841er.c:2282:1: warning: the frame size of 4336 bytes is larger than 2048 bytes [-Wframe-larger-than=]
1 ../drivers/media/dvb-frontends/cxd2841er.c:2282:1: warning: the frame size of 4328 bytes is larger than 2048 bytes [-Wframe-larger-than=]
===============================================================================
Detailed per-defconfig build reports below:
-------------------------------------------------------------------------------
arm64-allmodconfig : PASS, 0 errors, 19 warnings, 0 section mismatches
Warnings:
warning: (IMA) selects TCG_CRB which has unmet direct dependencies (TCG_TPM && X86 && ACPI)
warning: (IMA) selects TCG_CRB which has unmet direct dependencies (TCG_TPM && X86 && ACPI)
warning: (IMA) selects TCG_CRB which has unmet direct dependencies (TCG_TPM && X86 && ACPI)
../drivers/media/dvb-frontends/stv090x.c:1858:1: warning: the frame size of 2992 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:2141:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:2513:1: warning: the frame size of 2288 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:4565:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1956:1: warning: the frame size of 3248 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1599:1: warning: the frame size of 5280 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1211:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:4250:1: warning: the frame size of 4832 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1168:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:2073:1: warning: the frame size of 2544 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:3095:1: warning: the frame size of 5840 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:3436:1: warning: the frame size of 6784 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv0367.c:2490:1: warning: the frame size of 3424 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/cxd2841er.c:2401:1: warning: the frame size of 2976 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/cxd2841er.c:2282:1: warning: the frame size of 4336 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/net/ethernet/rocker/rocker.c:2172:1: warning: the frame size of 2720 bytes is larger than 2048 bytes [-Wframe-larger-than=]
-------------------------------------------------------------------------------
x86_64-allmodconfig : PASS, 0 errors, 17 warnings, 0 section mismatches
Warnings:
../drivers/media/dvb-frontends/stv090x.c:1858:1: warning: the frame size of 3008 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:2141:1: warning: the frame size of 2104 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:2513:1: warning: the frame size of 2304 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:4565:1: warning: the frame size of 2096 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1956:1: warning: the frame size of 3264 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1599:1: warning: the frame size of 5296 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1211:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:4250:1: warning: the frame size of 4832 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:4759:1: warning: the frame size of 2056 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:1168:1: warning: the frame size of 2080 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:2073:1: warning: the frame size of 2552 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:3095:1: warning: the frame size of 5864 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv090x.c:3436:1: warning: the frame size of 5280 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/stv0367.c:3147:1: warning: the frame size of 4144 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/cxd2841er.c:2401:1: warning: the frame size of 2984 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/media/dvb-frontends/cxd2841er.c:2282:1: warning: the frame size of 4328 bytes is larger than 2048 bytes [-Wframe-larger-than=]
../drivers/net/ethernet/rocker/rocker.c:2172:1: warning: the frame size of 2752 bytes is larger than 2048 bytes [-Wframe-larger-than=]
-------------------------------------------------------------------------------
Passed with no errors, warnings or mismatches:
arm64-allnoconfig
arm-multi_v5_defconfig
arm-multi_v7_defconfig
x86_64-defconfig
arm-allmodconfig
arm-allnoconfig
x86_64-allnoconfig
arm64-defconfig
From: Ville Syrjälä <ville.syrjala(a)linux.intel.com>
On i965/g4x IIR is edge triggered. So in order for IIR to notice that
there is still a pending interrupt we have to force and edge in ISR.
For the ISR/IIR pipe event bits we can do that by temporarily
clearing all the PIPESTAT enable bits when we ack the status bits.
This will force the ISR pipe event bit low, and it can then go back
high when we restore the PIPESTAT enable bits.
This avoids the following race:
1. stat = read(PIPESTAT)
2. an enabled PIPESTAT status bit goes high
3. write(PIPESTAT, enable|stat);
4. write(IIR, PIPE_EVENT)
The end result is IIR==0 and ISR!=0. This can lead to nasty
vblank wait/flip_done timeouts if another interrupt source
doesn't trick us into looking at the PIPESTAT status bits despite
the IIR PIPE_EVENT bit being low.
Before i965 IIR was level triggered so this problem can't actually
happen there. And curiously VLV/CHV went back to the level triggered
scheme as well. But for simplicity we'll use the same i965/g4x
compatible code for all platforms.
Cc: stable(a)vger.kernel.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106033
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105225
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106030
Signed-off-by: Ville Syrjälä <ville.syrjala(a)linux.intel.com>
---
drivers/gpu/drm/i915/i915_irq.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 2fd92a886789..364e1c85315e 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1893,9 +1893,17 @@ static void i9xx_pipestat_irq_ack(struct drm_i915_private *dev_priv,
/*
* Clear the PIPE*STAT regs before the IIR
+ *
+ * Toggle the enable bits to make sure we get an
+ * edge in the ISR pipe event bit if we don't clear
+ * all the enabled status bits. Otherwise the edge
+ * triggered IIR on i965/g4x wouldn't notice that
+ * an interrupt is still pending.
*/
- if (pipe_stats[pipe])
- I915_WRITE(reg, enable_mask | pipe_stats[pipe]);
+ if (pipe_stats[pipe]) {
+ I915_WRITE(reg, pipe_stats[pipe]);
+ I915_WRITE(reg, enable_mask);
+ }
}
spin_unlock(&dev_priv->irq_lock);
}
--
2.16.4