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Commit 92a476cb authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Marcelo Tosatti
Browse files

KVM: MMU: properly check last spte in fast_page_fault() 



Using sp->role.level instead of @level since @level is not got from the
page table hierarchy

There is no issue in current code since the fast page fault currently only
fixes the fault caused by dirty-log that is always on the last level
(level = 1)

This patch makes the code more readable and avoids potential issue in the
further development

Reviewed-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent a086f6a1

arch/x86/kvm/mmu.c

+6 −4
Original line number Diff line number Diff line
@@ -2802,9 +2802,9 @@ static bool page_fault_can_be_fast(u32 error_code) 
}



static bool

fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 spte)

fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,

			u64 *sptep, u64 spte)

{

	struct kvm_mmu_page *sp = page_header(__pa(sptep));

	gfn_t gfn;



	WARN_ON(!sp->role.direct);
@@ -2830,6 +2830,7 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level, 
			    u32 error_code)

{

	struct kvm_shadow_walk_iterator iterator;

	struct kvm_mmu_page *sp;

	bool ret = false;

	u64 spte = 0ull;
@@ -2853,7 +2854,8 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level, 
		goto exit;

	}



	if (!is_last_spte(spte, level))

	sp = page_header(__pa(iterator.sptep));

	if (!is_last_spte(spte, sp->role.level))

		goto exit;



	/*
@@ -2879,7 +2881,7 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level, 
	 * the gfn is not stable for indirect shadow page.

	 * See Documentation/virtual/kvm/locking.txt to get more detail.

	 */

	ret = fast_pf_fix_direct_spte(vcpu, iterator.sptep, spte);

	ret = fast_pf_fix_direct_spte(vcpu, sp, iterator.sptep, spte);

exit:

	trace_fast_page_fault(vcpu, gva, error_code, iterator.sptep,

			      spte, ret);