Re: [PATCH 4/5] KVM: MMU: move adjusting softmmu pte access toFNAME(page_fault)

[Marcelo Tosatti]

On Mon, Nov 05, 2012 at 08:12:07PM +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@xxxxxxxxxxxxxxxxxx>
>  arch/x86/kvm/mmu.c         |   42 +++++++++++-------------------------------
>  arch/x86/kvm/paging_tmpl.h |   25 ++++++++++++++++++++-----
>  2 files changed, 31 insertions(+), 36 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 49957df..4229e78 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2351,8 +2351,7 @@ static bool gfn_need_write_protect(struct kvm_vcpu *vcpu, u64 *sptep,
> 
>  /* The return value indicates whether the @gfn need to be write protected. */
>  static bool vcpu_adjust_access(struct kvm_vcpu *vcpu, u64 *sptep,
> -			       unsigned *pte_access, int user_fault,
> -			       int write_fault, int level, gfn_t gfn,
> +			       unsigned *pte_access, int level, gfn_t gfn,
>  			       bool can_unsync, bool host_writable)
>  {
>  	bool ret = false;
> @@ -2361,21 +2360,6 @@ static bool vcpu_adjust_access(struct kvm_vcpu *vcpu, u64 *sptep,
>  	if (!host_writable)
>  		access &= ~ACC_WRITE_MASK;
> 
> -	if (!(access & ACC_WRITE_MASK) && (!vcpu->arch.mmu.direct_map &&
> -	      write_fault && !is_write_protection(vcpu) && !user_fault)) {
> -		access |= ACC_WRITE_MASK;
> -		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))
> -			access &= ~ACC_EXEC_MASK;
> -	}
> -
>  	if ((access & ACC_WRITE_MASK) &&
>  		  gfn_need_write_protect(vcpu, sptep, level, gfn, can_unsync)) {
>  		access &= ~ACC_WRITE_MASK;
> @@ -2387,8 +2371,7 @@ static bool vcpu_adjust_access(struct kvm_vcpu *vcpu, u64 *sptep,
>  }
> 
>  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)
>  {
> @@ -2398,8 +2381,8 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  	if (set_mmio_spte(sptep, gfn, pfn, pte_access))
>  		return 0;
> 
> -	ret = vcpu_adjust_access(vcpu, sptep, &pte_access, user_fault,
> -		      write_fault, level, gfn, can_unsync, host_writable);
> +	ret = vcpu_adjust_access(vcpu, sptep, &pte_access, level, gfn,
> +				 can_unsync, host_writable);
> 
>  	spte = PT_PRESENT_MASK;
>  	if (!speculative)
> @@ -2440,17 +2423,14 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> 
>  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,
> +			 int write_fault, int *emulate, int level,
> +			 gfn_t gfn, pfn_t pfn, bool speculative,
>  			 bool host_writable)
>  {
>  	bool was_rmapped = false;
> 
> -	pgprintk("%s: spte %llx access %x write_fault %d"
> -		 " user_fault %d gfn %llx\n",
> -		 __func__, *sptep, pt_access,
> -		 write_fault, user_fault, gfn);
> +	pgprintk("%s: spte %llx access %x write_fault %d gfn %llx\n",
> +		 __func__, *sptep, pt_access, write_fault, gfn);
> 
>  	if (is_rmap_spte(*sptep)) {
>  		if (pfn != spte_to_pfn(*sptep)) {
> @@ -2462,7 +2442,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  			was_rmapped = true;
>  	}
> 
> -	if (set_spte(vcpu, sptep, pte_access, user_fault, write_fault,
> +	if (set_spte(vcpu, sptep, pte_access,
>  		      level, gfn, pfn, speculative, true,
>  		      host_writable)) {
>  		if (write_fault)
> @@ -2556,7 +2536,7 @@ static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
> 
>  	for (i = 0; i < ret; i++, gfn++, start++)
>  		mmu_set_spte(vcpu, start, ACC_ALL,
> -			     access, 0, 0, NULL,
> +			     access, 0, NULL,
>  			     sp->role.level, gfn,
>  			     page_to_pfn(pages[i]), true, true);
> 
> @@ -2620,7 +2600,7 @@ 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,
> +				     write, &emulate,
>  				     level, gfn, pfn, prefault, map_writable);
>  			direct_pte_prefetch(vcpu, iterator.sptep);
>  			++vcpu->stat.pf_fixed;
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 891eb6d..b1bcd68 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;
> +	}
> +

What about sync_page path?

>  	if (walker.level >= PT_DIRECTORY_LEVEL)
>  		force_pt_level = mapping_level_dirty_bitmap(vcpu, walker.gfn);
>  	else
> @@ -572,7 +587,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
>  	kvm_mmu_free_some_pages(vcpu);
>  	if (!force_pt_level)
>  		transparent_hugepage_adjust(vcpu, &walker.gfn, &pfn, &level);
> -	r = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
> +	r = FNAME(fetch)(vcpu, addr, &walker, write_fault,
>  			 level, pfn, map_writable, prefault);
>  	++vcpu->stat.pf_fixed;
>  	kvm_mmu_audit(vcpu, AUDIT_POST_PAGE_FAULT);
> @@ -747,7 +762,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
> 
>  		host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE;
> 
> -		set_spte(vcpu, &sp->spt[i], pte_access, 0, 0,
> +		set_spte(vcpu, &sp->spt[i], pte_access,
>  			 PT_PAGE_TABLE_LEVEL, gfn,
>  			 spte_to_pfn(sp->spt[i]), true, false,
>  			 host_writable);
> -- 
> 1.7.7.6
> 
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