2983660f65
CVE-2013-4377: Fix crash when unplugging virtio devices (bz #1012633, bz #1012641) Fix 'new snapshot' slowness after the first snap (bz #988436) Fix 9pfs xattrs on kernel 3.11 (bz #1013676) CVE-2013-4344: buffer overflow in scsi_target_emulate_report_luns (bz #1015274, bz #1007330)
44 lines
1.7 KiB
Diff
44 lines
1.7 KiB
Diff
From 57ea2d21ae1863fd4002b2aea8ea8db8e206d464 Mon Sep 17 00:00:00 2001
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From: Andrea Arcangeli <aarcange@redhat.com>
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Date: Thu, 25 Jul 2013 12:11:15 +0200
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Subject: [PATCH] exec: always use MADV_DONTFORK
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MADV_DONTFORK prevents fork to fail with -ENOMEM if the default
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overcommit heuristics decides there's too much anonymous virtual
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memory allocated. If the KVM secondary MMU is synchronized with MMU
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notifiers or not, doesn't make a difference in that regard.
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Secondly it's always more efficient to avoid copying the guest
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physical address space in the fork child (so we avoid to mark all the
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guest memory readonly in the parent and so we skip the establishment
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and teardown of lots of pagetables in the child).
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In the common case we can ignore the error if MADV_DONTFORK is not
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available. Leave a second invocation that errors out in the KVM path
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if MMU notifiers are missing and KVM is enabled, to abort in such
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case.
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Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
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Tested-By: Benoit Canet <benoit@irqsave.net>
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Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Gleb Natapov <gleb@redhat.com>
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(cherry picked from commit 3e469dbfe413c25d48321c3a19ddfae0727dc6e5)
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Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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---
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exec.c | 1 +
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1 file changed, 1 insertion(+)
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diff --git a/exec.c b/exec.c
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index 394f7e2..2ea8f04 100644
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--- a/exec.c
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+++ b/exec.c
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@@ -1172,6 +1172,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
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qemu_ram_setup_dump(new_block->host, size);
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qemu_madvise(new_block->host, size, QEMU_MADV_HUGEPAGE);
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+ qemu_madvise(new_block->host, size, QEMU_MADV_DONTFORK);
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if (kvm_enabled())
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kvm_setup_guest_memory(new_block->host, size);
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