On Thu, Sep 10, 2009 at 07:38:57PM +0300, Izik Eidus wrote:
> this flag notify that the host physical page we are pointing to from
> the spte is write protected, and therefore we cant change its access
> to be write unless we run get_user_pages(write = 1).
>
> (this is needed for change_pte support in kvm)
>
> Signed-off-by: Izik Eidus <ieidus@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 15 +++++++++++----
> arch/x86/kvm/paging_tmpl.h | 18 +++++++++++++++---
> 2 files changed, 26 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 62d2f86..a7151b8 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -156,6 +156,8 @@ module_param(oos_shadow, bool, 0644);
> #define CREATE_TRACE_POINTS
> #include "mmutrace.h"
>
> +#define SPTE_HOST_WRITEABLE (1ULL << PT_FIRST_AVAIL_BITS_SHIFT)
> +
> #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
>
> struct kvm_rmap_desc {
> @@ -1754,7 +1756,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> unsigned pte_access, int user_fault,
> int write_fault, int dirty, int level,
> gfn_t gfn, pfn_t pfn, bool speculative,
> - bool can_unsync)
> + bool can_unsync, bool reset_host_protection)
> {
> u64 spte;
> int ret = 0;
> @@ -1781,6 +1783,9 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> spte |= kvm_x86_ops->get_mt_mask(vcpu, gfn,
> kvm_is_mmio_pfn(pfn));
>
> + if (reset_host_protection)
> + spte |= SPTE_HOST_WRITEABLE;
> +
> spte |= (u64)pfn << PAGE_SHIFT;
>
> if ((pte_access & ACC_WRITE_MASK)
> @@ -1826,7 +1831,8 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> unsigned pt_access, unsigned pte_access,
> int user_fault, int write_fault, int dirty,
> int *ptwrite, int level, gfn_t gfn,
> - pfn_t pfn, bool speculative)
> + pfn_t pfn, bool speculative,
> + bool reset_host_protection)
> {
> int was_rmapped = 0;
> int was_writeble = is_writeble_pte(*sptep);
> @@ -1858,7 +1864,8 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> }
>
> if (set_spte(vcpu, sptep, pte_access, user_fault, write_fault,
> - dirty, level, gfn, pfn, speculative, true)) {
> + dirty, level, gfn, pfn, speculative, true,
> + reset_host_protection)) {
> if (write_fault)
> *ptwrite = 1;
> kvm_x86_ops->tlb_flush(vcpu);
> @@ -1906,7 +1913,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
> if (iterator.level == level) {
> mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, ACC_ALL,
> 0, write, 1, &pt_write,
> - level, gfn, pfn, false);
> + level, gfn, pfn, false, true);
> ++vcpu->stat.pf_fixed;
> break;
> }
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index d2fec9c..c9256ee 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -273,9 +273,13 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page,
> if (mmu_notifier_retry(vcpu, vcpu->arch.update_pte.mmu_seq))
> return;
> kvm_get_pfn(pfn);
> + /*
> + * we call mmu_set_spte() with reset_host_protection = true beacuse that
> + * vcpu->arch.update_pte.pfn was fetched from get_user_pages(write = 1).
> + */
> mmu_set_spte(vcpu, spte, page->role.access, pte_access, 0, 0,
> gpte & PT_DIRTY_MASK, NULL, PT_PAGE_TABLE_LEVEL,
> - gpte_to_gfn(gpte), pfn, true);
> + gpte_to_gfn(gpte), pfn, true, true);
> }
>
> /*
> @@ -308,7 +312,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
> user_fault, write_fault,
> gw->ptes[gw->level-1] & PT_DIRTY_MASK,
> ptwrite, level,
> - gw->gfn, pfn, false);
> + gw->gfn, pfn, false, true);
> break;
> }
>
> @@ -558,6 +562,7 @@ static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
> static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
> {
> int i, offset, nr_present;
> + bool reset_host_protection;
>
> offset = nr_present = 0;
>
> @@ -595,9 +600,16 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
>
> nr_present++;
> pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
> + if (!(sp->spt[i] & SPTE_HOST_WRITEABLE)) {
> + pte_access &= ~PT_WRITABLE_MASK;
> + reset_host_protection = 0;
> + } else {
> + reset_host_protection = 1;
> + }
> set_spte(vcpu, &sp->spt[i], pte_access, 0, 0,
> is_dirty_gpte(gpte), PT_PAGE_TABLE_LEVEL, gfn,
> - spte_to_pfn(sp->spt[i]), true, false);
> + spte_to_pfn(sp->spt[i]), true, false,
> + reset_host_protection);
Why can't you use the writable bit in the spte? So that you can only
sync a writeable spte if it was writeable before, in sync_page?
Is there any other need for the extra bit?
> }
>
> return !nr_present;
> --
> 1.5.6.5
>
> --
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