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hw/virtio/balloon: Replace TARGET_PAGE_SIZE with BALLOON_PAGE_SIZE 

The balloon code currently calls madvise() with TARGET_PAGE_SIZE as
length parameter. Since the virtio-balloon protocol is always based
on 4k pages, no matter what the host and guest are using as page size,
this could cause problems: If TARGET_PAGE_SIZE is bigger than 4k, the
madvise call also destroys the 4k areas after the current one - which
might be wrong since the guest did not want free that area yet (in
case the guest used as smaller MMU page size than the hard-coded
TARGET_PAGE_SIZE). So to fix this issue, introduce a proper define
called BALLOON_PAGE_SIZE (which is 4096) to use this as the size
parameter for the madvise() call instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Thomas Huth 2016-04-14 10:50:07 +02:00 committed by Michael S. Tsirkin
parent e7658fcc4c
commit 01310e2aa7
1 changed files with 3 additions and 2 deletions
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5
hw/virtio/virtio-balloon.c
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@ -19,7 +19,6 @@
#include "qemu-common.h" #include "qemu-common.h"
#include "hw/virtio/virtio.h" #include "hw/virtio/virtio.h"
#include "hw/i386/pc.h" #include "hw/i386/pc.h"
#include "cpu.h"
#include "sysemu/balloon.h" #include "sysemu/balloon.h"
#include "hw/virtio/virtio-balloon.h" #include "hw/virtio/virtio-balloon.h"
#include "sysemu/kvm.h" #include "sysemu/kvm.h"
@ -35,12 +34,14 @@
#include "hw/virtio/virtio-bus.h" #include "hw/virtio/virtio-bus.h"
#include "hw/virtio/virtio-access.h" #include "hw/virtio/virtio-access.h"
#define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT)
static void balloon_page(void *addr, int deflate) static void balloon_page(void *addr, int deflate)
{ {
#if defined(__linux__) #if defined(__linux__)
if (!qemu_balloon_is_inhibited() && (!kvm_enabled() || if (!qemu_balloon_is_inhibited() && (!kvm_enabled() ||
kvm_has_sync_mmu())) { kvm_has_sync_mmu())) {
qemu_madvise(addr, TARGET_PAGE_SIZE, qemu_madvise(addr, BALLOON_PAGE_SIZE,
deflate ? QEMU_MADV_WILLNEED : QEMU_MADV_DONTNEED); deflate ? QEMU_MADV_WILLNEED : QEMU_MADV_DONTNEED);
} }
#endif #endif