On Mon, Jun 21, 2010 at 11:18:13AM +0300, Avi Kivity wrote:
> If a process with a memory slot is COWed, the page will change its address
> (despite having an elevated reference count). This breaks internal memory
> slots which have their physical addresses loaded into vmcs registers (see
> the APIC access memory slot).
>
> Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 5 +++++
> 1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 33156a3..d9a33e6 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5633,6 +5633,11 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
> int user_alloc)
> {
> int npages = memslot->npages;
> + int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
> +
> + /* Prevent internal slot pages from being moved by fork()/COW. */
> + if (memslot->id >= KVM_MEMORY_SLOTS)
> + map_flags = MAP_SHARED | MAP_ANONYMOUS;
>
> /*To keep backward compatibility with older userspace,
> *x86 needs to hanlde !user_alloc case.
Forgot to use map_flags below.
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