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Commit fe135d2c authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: MMU: Simplify calculation of pte access 



The nx bit is awkwardly placed in the 63rd bit position; furthermore it
has a reversed meaning compared to the other bits, which means we can't use
a bitwise and to calculate compounded access masks.

So, we simplify things by creating a new 3-bit exec/write/user access word,
and doing all calculations in that.

Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent b3e4e63f

drivers/kvm/mmu.c

+10 −4
Original line number Diff line number Diff line
@@ -85,7 +85,8 @@ static int dbg = 1; 
#define PT_PAGE_SIZE_MASK (1ULL << 7)

#define PT_PAT_MASK (1ULL << 7)

#define PT_GLOBAL_MASK (1ULL << 8)

#define PT64_NX_MASK (1ULL << 63)

#define PT64_NX_SHIFT 63

#define PT64_NX_MASK (1ULL << PT64_NX_SHIFT)



#define PT_PAT_SHIFT 7

#define PT_DIR_PAT_SHIFT 12
@@ -153,6 +154,11 @@ static int dbg = 1; 


#define RMAP_EXT 4



#define ACC_EXEC_MASK    1

#define ACC_WRITE_MASK   PT_WRITABLE_MASK

#define ACC_USER_MASK    PT_USER_MASK

#define ACC_ALL          (ACC_EXEC_MASK | ACC_WRITE_MASK | ACC_USER_MASK)



struct kvm_rmap_desc {

	u64 *shadow_ptes[RMAP_EXT];

	struct kvm_rmap_desc *more;
@@ -921,7 +927,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, struct page *page) 
				>> PAGE_SHIFT;

			new_table = kvm_mmu_get_page(vcpu, pseudo_gfn,

						     v, level - 1,

						     1, 3, &table[index]);

						     1, ACC_ALL, &table[index]);

			if (!new_table) {

				pgprintk("nonpaging_map: ENOMEM\n");

				kvm_release_page_clean(page);
@@ -988,7 +994,7 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu) 


		ASSERT(!VALID_PAGE(root));

		sp = kvm_mmu_get_page(vcpu, root_gfn, 0,

				      PT64_ROOT_LEVEL, 0, 0, NULL);

				      PT64_ROOT_LEVEL, 0, ACC_ALL, NULL);

		root = __pa(sp->spt);

		++sp->root_count;

		vcpu->mmu.root_hpa = root;
@@ -1009,7 +1015,7 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu) 
			root_gfn = 0;

		sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30,

				      PT32_ROOT_LEVEL, !is_paging(vcpu),

				      0, NULL);

				      ACC_ALL, NULL);

		root = __pa(sp->spt);

		++sp->root_count;

		vcpu->mmu.pae_root[i] = root | PT_PRESENT_MASK;

drivers/kvm/paging_tmpl.h

+33 −25
Original line number Diff line number Diff line
@@ -66,7 +66,8 @@ struct guest_walker { 
	int level;

	gfn_t table_gfn[PT_MAX_FULL_LEVELS];

	pt_element_t pte;

	pt_element_t inherited_ar;

	unsigned pt_access;

	unsigned pte_access;

	gfn_t gfn;

	u32 error_code;

};
@@ -110,7 +111,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker, 
{

	pt_element_t pte;

	gfn_t table_gfn;

	unsigned index;

	unsigned index, pt_access, pte_access;

	gpa_t pte_gpa;



	pgprintk("%s: addr %lx\n", __FUNCTION__, addr);
@@ -128,7 +129,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker, 
	ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) ||

	       (vcpu->cr3 & CR3_NONPAE_RESERVED_BITS) == 0);



	walker->inherited_ar = PT_USER_MASK | PT_WRITABLE_MASK;

	pt_access = ACC_ALL;



	for (;;) {

		index = PT_INDEX(addr, walker->level);
@@ -165,6 +166,14 @@ static int FNAME(walk_addr)(struct guest_walker *walker, 
			pte |= PT_ACCESSED_MASK;

		}



		pte_access = pte & (PT_WRITABLE_MASK | PT_USER_MASK);

		pte_access |= ACC_EXEC_MASK;

#if PTTYPE == 64

		if (is_nx(vcpu))

			pte_access &= ~(pte >> PT64_NX_SHIFT);

#endif

		pte_access &= pt_access;



		if (walker->level == PT_PAGE_TABLE_LEVEL) {

			walker->gfn = gpte_to_gfn(pte);

			break;
@@ -180,7 +189,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker, 
			break;

		}



		walker->inherited_ar &= pte;

		pt_access = pte_access;

		--walker->level;

	}
@@ -197,7 +206,10 @@ static int FNAME(walk_addr)(struct guest_walker *walker, 
	}



	walker->pte = pte;

	pgprintk("%s: pte %llx\n", __FUNCTION__, (u64)pte);

	walker->pt_access = pt_access;

	walker->pte_access = pte_access;

	pgprintk("%s: pte %llx pte_access %x pt_access %x\n",

		 __FUNCTION__, (u64)pte, pt_access, pte_access);

	return 1;



not_present:
@@ -218,7 +230,8 @@ static int FNAME(walk_addr)(struct guest_walker *walker, 
}



static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte,

			   u64 *shadow_pte, u64 access_bits,

			   u64 *shadow_pte, unsigned pt_access,

			   unsigned pte_access,

			   int user_fault, int write_fault,

			   int *ptwrite, struct guest_walker *walker,

			   gfn_t gfn)
@@ -228,12 +241,11 @@ static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte, 
	int was_rmapped = is_rmap_pte(*shadow_pte);

	struct page *page;



	pgprintk("%s: spte %llx gpte %llx access %llx write_fault %d"

	pgprintk("%s: spte %llx gpte %llx access %x write_fault %d"

		 " user_fault %d gfn %lx\n",

		 __FUNCTION__, *shadow_pte, (u64)gpte, access_bits,

		 __FUNCTION__, *shadow_pte, (u64)gpte, pt_access,

		 write_fault, user_fault, gfn);



	access_bits &= gpte;

	/*

	 * We don't set the accessed bit, since we sometimes want to see

	 * whether the guest actually used the pte (in order to detect
@@ -242,12 +254,12 @@ static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte, 
	spte = PT_PRESENT_MASK | PT_DIRTY_MASK;

	spte |= gpte & PT64_NX_MASK;

	if (!dirty)

		access_bits &= ~PT_WRITABLE_MASK;

		pte_access &= ~ACC_WRITE_MASK;



	page = gfn_to_page(vcpu->kvm, gfn);



	spte |= PT_PRESENT_MASK;

	if (access_bits & PT_USER_MASK)

	if (pte_access & ACC_USER_MASK)

		spte |= PT_USER_MASK;



	if (is_error_page(page)) {
@@ -259,7 +271,7 @@ static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte, 


	spte |= page_to_phys(page);



	if ((access_bits & PT_WRITABLE_MASK)

	if ((pte_access & ACC_WRITE_MASK)

	    || (write_fault && !is_write_protection(vcpu) && !user_fault)) {

		struct kvm_mmu_page *shadow;
@@ -273,7 +285,7 @@ static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte, 
		if (shadow) {

			pgprintk("%s: found shadow page for %lx, marking ro\n",

				 __FUNCTION__, gfn);

			access_bits &= ~PT_WRITABLE_MASK;

			pte_access &= ~ACC_WRITE_MASK;

			if (is_writeble_pte(spte)) {

				spte &= ~PT_WRITABLE_MASK;

				kvm_x86_ops->tlb_flush(vcpu);
@@ -285,7 +297,7 @@ static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte, 


unshadowed:



	if (access_bits & PT_WRITABLE_MASK)

	if (pte_access & ACC_WRITE_MASK)

		mark_page_dirty(vcpu->kvm, gfn);



	pgprintk("%s: setting spte %llx\n", __FUNCTION__, spte);
@@ -317,8 +329,8 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page, 
	if (bytes < sizeof(pt_element_t))

		return;

	pgprintk("%s: gpte %llx spte %p\n", __FUNCTION__, (u64)gpte, spte);

	FNAME(set_pte)(vcpu, gpte, spte, PT_USER_MASK | PT_WRITABLE_MASK, 0,

		       0, NULL, NULL, gpte_to_gfn(gpte));

	FNAME(set_pte)(vcpu, gpte, spte, ACC_ALL, ACC_ALL,

		       0, 0, NULL, NULL, gpte_to_gfn(gpte));

}



/*
@@ -331,6 +343,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 
	hpa_t shadow_addr;

	int level;

	u64 *shadow_ent;

	unsigned access = walker->pt_access;



	if (!is_present_pte(walker->pte))

		return NULL;
@@ -349,7 +362,6 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 
		u64 shadow_pte;

		int metaphysical;

		gfn_t table_gfn;

		unsigned hugepage_access = 0;



		shadow_ent = ((u64 *)__va(shadow_addr)) + index;

		if (is_shadow_present_pte(*shadow_ent)) {
@@ -365,20 +377,15 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 
		if (level - 1 == PT_PAGE_TABLE_LEVEL

		    && walker->level == PT_DIRECTORY_LEVEL) {

			metaphysical = 1;

			hugepage_access = walker->pte;

			hugepage_access &= PT_USER_MASK | PT_WRITABLE_MASK;

			if (!is_dirty_pte(walker->pte))

				hugepage_access &= ~PT_WRITABLE_MASK;

			hugepage_access >>= PT_WRITABLE_SHIFT;

			if (walker->pte & PT64_NX_MASK)

				hugepage_access |= (1 << 2);

				access &= ~ACC_WRITE_MASK;

			table_gfn = gpte_to_gfn(walker->pte);

		} else {

			metaphysical = 0;

			table_gfn = walker->table_gfn[level - 2];

		}

		shadow_page = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1,

					       metaphysical, hugepage_access,

					       metaphysical, access,

					       shadow_ent);

		shadow_addr = __pa(shadow_page->spt);

		shadow_pte = shadow_addr | PT_PRESENT_MASK | PT_ACCESSED_MASK
@@ -387,7 +394,8 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 
	}



	FNAME(set_pte)(vcpu, walker->pte, shadow_ent,

		       walker->inherited_ar, user_fault, write_fault,

		       access, walker->pte_access & access,

		       user_fault, write_fault,

		       ptwrite, walker, walker->gfn);



	return shadow_ent;