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Subject[PATCH 02/12] KVM: MMU: properly check last spte in fast_page_fault()
Date
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 only fixes the
fault caused by dirty-log, that means no large spte points to the dirty logged
page

The patch makes the code more readable and avoid potential issue in the further
development

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
arch/x86/kvm/mmu.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a731c0b..cf163ca 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2830,9 +2830,9 @@ 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);
@@ -2858,6 +2858,7 @@ 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;

@@ -2878,7 +2879,8 @@ 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;

/*
@@ -2904,7 +2906,7 @@ 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);
--
1.8.1.4


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