Il 30/07/2013 15:02, Xiao Guangrong ha scritto:
> kvm_vm_ioctl_get_dirty_log() write-protects the spte based on the dirty
> bitmap, we should ensure the writable spte can be found in rmap before the
> dirty bitmap is visible. Otherwise, we cleared the dirty bitmap and failed
> to write-protect the page
>
> It need the memory barrier to prevent out-of-order that will be added in the
> later patch
Do you mean that the later patch will also introduce a memory barrier?
Paolo
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 25 ++++++++++---------------
> 1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 0fe56ad..58283bf 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2425,6 +2425,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> {
> u64 spte;
> int ret = 0;
> + bool remap = is_rmap_spte(*sptep);
>
> if (set_mmio_spte(vcpu->kvm, sptep, gfn, pfn, pte_access))
> return 0;
> @@ -2490,6 +2491,14 @@ set_pte:
> if (mmu_spte_update(sptep, spte))
> kvm_flush_remote_tlbs(vcpu->kvm);
>
> + if (!remap) {
> + if (rmap_add(vcpu, sptep, gfn) > RMAP_RECYCLE_THRESHOLD)
> + rmap_recycle(vcpu, sptep, gfn);
> +
> + if (level > PT_PAGE_TABLE_LEVEL)
> + ++vcpu->kvm->stat.lpages;
> + }
> +
> if (pte_access & ACC_WRITE_MASK)
> mark_page_dirty(vcpu->kvm, gfn);
> done:
> @@ -2501,9 +2510,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> int level, gfn_t gfn, pfn_t pfn, bool speculative,
> bool host_writable)
> {
> - int was_rmapped = 0;
> - int rmap_count;
> -
> pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__,
> *sptep, write_fault, gfn);
>
> @@ -2525,8 +2531,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> spte_to_pfn(*sptep), pfn);
> drop_spte(vcpu->kvm, sptep);
> kvm_flush_remote_tlbs(vcpu->kvm);
> - } else
> - was_rmapped = 1;
> + }
> }
>
> if (set_spte(vcpu, sptep, pte_access, level, gfn, pfn, speculative,
> @@ -2544,16 +2549,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> is_large_pte(*sptep)? "2MB" : "4kB",
> *sptep & PT_PRESENT_MASK ?"RW":"R", gfn,
> *sptep, sptep);
> - if (!was_rmapped && is_large_pte(*sptep))
> - ++vcpu->kvm->stat.lpages;
> -
> - if (is_shadow_present_pte(*sptep)) {
> - if (!was_rmapped) {
> - rmap_count = rmap_add(vcpu, sptep, gfn);
> - if (rmap_count > RMAP_RECYCLE_THRESHOLD)
> - rmap_recycle(vcpu, sptep, gfn);
> - }
> - }
>
> kvm_release_pfn_clean(pfn);
> }
>
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