Il 20/06/2013 18:34, Takuya Yoshikawa ha scritto:
> From: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
>
> Without this information, users will just see unexpected performance
> problems and there is little chance we will get good reports from them:
> note that mmio generation is increased even when we just start, or stop,
> dirty logging for some memory slot, in which case users cannot expect
> all shadow pages to be zapped.
>
> printk_ratelimited() is used for this taking into account the problems
> that we can see the information many times when we start multiple VMs
> and guests can trigger this by reading ROM in a loop for example.
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
> ---
> Interestingly, I saw this information printed twice every time.
> Looks like current_mmio_gen can become mmio_max_gen...
> arch/x86/kvm/mmu.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index c60c5da..54e3968 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4385,8 +4385,10 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
> * The max value is MMIO_MAX_GEN - 1 since it is not called
> * when mark memslot invalid.
> */
> - if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1)))
> + if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1))) {
There is an off-by-one here (that I can fix in a separate patch). The
right test is >= MMIO_MAX_GEN, since we have:
#define MMIO_MAX_GEN ((1 << MMIO_GEN_SHIFT) - 1)
Paolo
> + printk_ratelimited(KERN_INFO "kvm: zapping shadow pages for mmio generation wraparound\n");
> kvm_mmu_invalidate_zap_all_pages(kvm);
> + }
> }
>
> static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
>
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