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From 38dcbd1ff68da81b9172d8036622e41fe591c5c0 Mon Sep 17 00:00:00 2001
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From: Andrea Arcangeli <aarcange@redhat.com>
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Date: Fri, 7 Feb 2014 11:02:33 +0100
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Subject: [PATCH 10/28] exec: always use MADV_DONTFORK
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RH-Author: Andrea Arcangeli <aarcange@redhat.com>
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Message-id: <1391770953-20138-2-git-send-email-aarcange@redhat.com>
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Patchwork-id: 57131
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O-Subject: [RHEL-7.0 qemu-kvm PATCH] exec: always use MADV_DONTFORK
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Bugzilla: 1004197
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Andrew Jones <drjones@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
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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 upstream commit 3e469dbfe413c25d48321c3a19ddfae0727dc6e5)
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---
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exec.c | 1 +
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1 file changed, 1 insertion(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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exec.c | 1 +
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1 files changed, 1 insertions(+), 0 deletions(-)
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diff --git a/exec.c b/exec.c
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index ce9310c..6fe2fe7 100644
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--- a/exec.c
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+++ b/exec.c
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@@ -1194,6 +1194,7 @@ 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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--
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1.7.1
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