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SubjectRe: [PATCH 3/3] KVM: MMU: track the refcount when unmap the page
On Tue, Jul 03, 2012 at 02:32:14PM +0800, Xiao Guangrong wrote:
> It will trigger a WARN_ON if the page has been freed but it is still
> used in mmu, it can help us to detect mm bug early
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
> ---
> arch/x86/kvm/mmu.c | 8 ++++++++
> 1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index cac3408..af7e076 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -527,6 +527,14 @@ static int mmu_spte_clear_track_bits(u64 *sptep)
> return 0;
>
> pfn = spte_to_pfn(old_spte);
> +
> + /*
> + * KVM does not hold the refcount of the page used by
> + * kvm mmu, before reclaiming the page, we should
> + * unmap it from mmu first.
> + */
> + WARN_ON(!page_count(pfn_to_page(pfn)));
> +

Except for mmio pfns.

Applied patch 1 and 2 to master, thanks.



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