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Date: Tue, 11 Dec 2012 21:47:51 -0200
From: Marcelo Tosatti <mtosatti@...hat.com>
To: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc: Gleb Natapov <gleb@...hat.com>,
LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] KVM: MMU: move adjusting pte access for softmmu
to FNAME(page_fault)
On Mon, Dec 10, 2012 at 05:12:20PM +0800, Xiao Guangrong wrote:
> Then, no mmu specified code exists in the common function and drop two
> parameters in set_spte
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> ---
> arch/x86/kvm/mmu.c | 47 ++++++++++++-------------------------------
> arch/x86/kvm/paging_tmpl.h | 25 ++++++++++++++++++----
> 2 files changed, 33 insertions(+), 39 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 01d7c2a..2a3c890 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2342,8 +2342,7 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
> }
>
> static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> - unsigned pte_access, int user_fault,
> - int write_fault, int level,
> + unsigned pte_access, int level,
> gfn_t gfn, pfn_t pfn, bool speculative,
> bool can_unsync, bool host_writable)
> {
> @@ -2378,9 +2377,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>
> spte |= (u64)pfn << PAGE_SHIFT;
>
> - if ((pte_access & ACC_WRITE_MASK)
> - || (!vcpu->arch.mmu.direct_map && write_fault
> - && !is_write_protection(vcpu) && !user_fault)) {
> + if (pte_access & ACC_WRITE_MASK) {
>
> /*
> * There are two cases:
> @@ -2399,19 +2396,6 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>
> spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE;
>
> - if (!vcpu->arch.mmu.direct_map
> - && !(pte_access & ACC_WRITE_MASK)) {
> - spte &= ~PT_USER_MASK;
> - /*
> - * If we converted a user page to a kernel page,
> - * so that the kernel can write to it when cr0.wp=0,
> - * then we should prevent the kernel from executing it
> - * if SMEP is enabled.
> - */
> - if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
> - spte |= PT64_NX_MASK;
> - }
> -
> /*
> * Optimization: for pte sync, if spte was writable the hash
> * lookup is unnecessary (and expensive). Write protection
> @@ -2442,18 +2426,15 @@ done:
>
> static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> unsigned pt_access, unsigned pte_access,
> - int user_fault, int write_fault,
> - int *emulate, int level, gfn_t gfn,
> - pfn_t pfn, bool speculative,
> - bool host_writable)
> + int write_fault, int *emulate, int level, gfn_t gfn,
> + pfn_t pfn, bool speculative, bool host_writable)
> {
> int was_rmapped = 0;
> int rmap_count;
>
> - pgprintk("%s: spte %llx access %x write_fault %d"
> - " user_fault %d gfn %llx\n",
> + pgprintk("%s: spte %llx access %x write_fault %d gfn %llx\n",
> __func__, *sptep, pt_access,
> - write_fault, user_fault, gfn);
> + write_fault, gfn);
>
> if (is_rmap_spte(*sptep)) {
> /*
> @@ -2477,9 +2458,8 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> was_rmapped = 1;
> }
>
> - if (set_spte(vcpu, sptep, pte_access, user_fault, write_fault,
> - level, gfn, pfn, speculative, true,
> - host_writable)) {
> + if (set_spte(vcpu, sptep, pte_access, level, gfn, pfn, speculative,
> + true, host_writable)) {
> if (write_fault)
> *emulate = 1;
> kvm_mmu_flush_tlb(vcpu);
> @@ -2571,10 +2551,9 @@ static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
> return -1;
>
> for (i = 0; i < ret; i++, gfn++, start++)
> - mmu_set_spte(vcpu, start, ACC_ALL,
> - access, 0, 0, NULL,
> - sp->role.level, gfn,
> - page_to_pfn(pages[i]), true, true);
> + mmu_set_spte(vcpu, start, ACC_ALL, access, 0, NULL,
> + sp->role.level, gfn, page_to_pfn(pages[i]),
> + true, true);
>
> return 0;
> }
> @@ -2636,8 +2615,8 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
> unsigned pte_access = ACC_ALL;
>
> mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, pte_access,
> - 0, write, &emulate,
> - level, gfn, pfn, prefault, map_writable);
> + write, &emulate, level, gfn, pfn,
> + prefault, map_writable);
> direct_pte_prefetch(vcpu, iterator.sptep);
> ++vcpu->stat.pf_fixed;
> break;
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 891eb6d..ec481e9 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -330,7 +330,7 @@ FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> * we call mmu_set_spte() with host_writable = true because
> * pte_prefetch_gfn_to_pfn always gets a writable pfn.
> */
> - mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0,
> + mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0,
> NULL, PT_PAGE_TABLE_LEVEL, gfn, pfn, true, true);
>
> return true;
> @@ -405,7 +405,7 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
> */
> static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
> struct guest_walker *gw,
> - int user_fault, int write_fault, int hlevel,
> + int write_fault, int hlevel,
> pfn_t pfn, bool map_writable, bool prefault)
> {
> struct kvm_mmu_page *sp = NULL;
> @@ -478,7 +478,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
>
> clear_sp_write_flooding_count(it.sptep);
> mmu_set_spte(vcpu, it.sptep, access, gw->pte_access,
> - user_fault, write_fault, &emulate, it.level,
> + write_fault, &emulate, it.level,
> gw->gfn, pfn, prefault, map_writable);
> FNAME(pte_prefetch)(vcpu, gw, it.sptep);
>
> @@ -544,6 +544,21 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
> return 0;
> }
>
> + if (write_fault && !(walker.pte_access & ACC_WRITE_MASK) &&
> + !is_write_protection(vcpu) && !user_fault) {
> + walker.pte_access |= ACC_WRITE_MASK;
> + walker.pte_access &= ~ACC_USER_MASK;
> +
> + /*
> + * If we converted a user page to a kernel page,
> + * so that the kernel can write to it when cr0.wp=0,
> + * then we should prevent the kernel from executing it
> + * if SMEP is enabled.
> + */
> + if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
> + walker.pte_access &= ~ACC_EXEC_MASK;
> + }
Don't think you should modify walker.pte_access here, since it can be
used afterwards (eg for handle_abnormal_pfn).
BTW, your patch is fixing a bug:
host_writable is ignored for CR0.WP emulation:
if (host_writable)
spte |= SPTE_HOST_WRITEABLE;
else
pte_access &= ~ACC_WRITE_MASK;
spte |= (u64)pfn << PAGE_SHIFT;
if ((pte_access & ACC_WRITE_MASK)
|| (!vcpu->arch.mmu.direct_map && write_fault
&& !is_write_protection(vcpu) && !user_fault)) {
--
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