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Commit cd46868c authored by Yang, Wei Y's avatar Yang, Wei Y Committed by Avi Kivity
Browse files

KVM: MMU: Fix SMEP failure during fetch 



This patch fix kvm-unit-tests hanging and incorrect PT_ACCESSED_MASK
bit set in the case of SMEP fault.  The code updated 'eperm' after
the variable was checked.

Signed-off-by: default avatarYang, Wei <wei.y.yang@intel.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent e4e517b4

arch/x86/kvm/paging_tmpl.h

+13 −9
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 
	gfn_t table_gfn;

	unsigned index, pt_access, uninitialized_var(pte_access);

	gpa_t pte_gpa;

	bool eperm;

	bool eperm, last_gpte;

	int offset;

	const int write_fault = access & PFERR_WRITE_MASK;

	const int user_fault  = access & PFERR_USER_MASK;
@@ -221,6 +221,17 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 
			eperm = true;

#endif



		last_gpte = FNAME(is_last_gpte)(walker, vcpu, mmu, pte);

		if (last_gpte) {

			pte_access = pt_access &

				     FNAME(gpte_access)(vcpu, pte, true);

			/* check if the kernel is fetching from user page */

			if (unlikely(pte_access & PT_USER_MASK) &&

			    kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))

				if (fetch_fault && !user_fault)

					eperm = true;

		}



		if (!eperm && unlikely(!(pte & PT_ACCESSED_MASK))) {

			int ret;

			trace_kvm_mmu_set_accessed_bit(table_gfn, index,
@@ -238,18 +249,12 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 


		walker->ptes[walker->level - 1] = pte;



		if (FNAME(is_last_gpte)(walker, vcpu, mmu, pte)) {

		if (last_gpte) {

			int lvl = walker->level;

			gpa_t real_gpa;

			gfn_t gfn;

			u32 ac;



			/* check if the kernel is fetching from user page */

			if (unlikely(pte_access & PT_USER_MASK) &&

			    kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))

				if (fetch_fault && !user_fault)

					eperm = true;



			gfn = gpte_to_gfn_lvl(pte, lvl);

			gfn += (addr & PT_LVL_OFFSET_MASK(lvl)) >> PAGE_SHIFT;
@@ -295,7 +300,6 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 
		walker->ptes[walker->level - 1] = pte;

	}



	pte_access = pt_access & FNAME(gpte_access)(vcpu, pte, true);

	walker->pt_access = pt_access;

	walker->pte_access = pte_access;

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