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Subject[PATCH 08/16] KVM: x86/mmu: Incorporate guest's page level into max level for shadow MMU
Date
Restrict the max level for a shadow page based on the guest's level
instead of capping the level after the fact for host-mapped huge pages,
e.g. hugetlbfs pages. Explicitly capping the max level using the guest
mapping level also eliminates FNAME(page_fault)'s subtle dependency on
THP only supporting 2mb pages.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/mmu/paging_tmpl.h | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 1938a6e4e631..7d57ec576df0 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -773,7 +773,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
struct guest_walker walker;
int r;
kvm_pfn_t pfn;
- int level = PT_PAGE_TABLE_LEVEL;
+ int level;
unsigned long mmu_seq;
bool map_writable, is_self_change_mapping;
bool lpage_disallowed = (error_code & PFERR_FETCH_MASK) &&
@@ -818,18 +818,14 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu,
&walker, user_fault, &vcpu->arch.write_fault_to_shadow_pgtable);

- max_level = lpage_disallowed ? PT_PAGE_TABLE_LEVEL :
- PT_MAX_HUGEPAGE_LEVEL;
-
- if (walker.level >= PT_DIRECTORY_LEVEL && !is_self_change_mapping) {
- level = mapping_level(vcpu, walker.gfn, &max_level);
- if (likely(max_level > PT_DIRECTORY_LEVEL)) {
- level = min(walker.level, level);
- walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
- }
- } else {
+ if (lpage_disallowed || is_self_change_mapping)
max_level = PT_PAGE_TABLE_LEVEL;
- }
+ else
+ max_level = walker.level;
+
+ level = mapping_level(vcpu, walker.gfn, &max_level);
+ if (level > PT_PAGE_TABLE_LEVEL)
+ walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);

mmu_seq = vcpu->kvm->mmu_notifier_seq;
smp_rmb();
--
2.24.0
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