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Subject[PATCH 1/3] KVM: x86/mmu: Add helper macro for computing hugepage GFN mask
Date
Add a helper to compute the GFN mask given a hugepage level, KVM is
accumulating quite a few users with the addition of the TDP MMU.

Note, gcc is clever enough to use a single NEG instruction instead of
SUB+NOT, i.e. use the more common "~(level -1)" pattern instead of
round_gfn_for_level()'s direct two's complement trickery.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu/mmu.c | 2 +-
arch/x86/kvm/mmu/paging_tmpl.h | 4 ++--
arch/x86/kvm/mmu/tdp_iter.c | 2 +-
4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d44858b69353..6ea046415f29 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -119,6 +119,7 @@
#define KVM_HPAGE_SIZE(x) (1UL << KVM_HPAGE_SHIFT(x))
#define KVM_HPAGE_MASK(x) (~(KVM_HPAGE_SIZE(x) - 1))
#define KVM_PAGES_PER_HPAGE(x) (KVM_HPAGE_SIZE(x) / PAGE_SIZE)
+#define KVM_HPAGE_GFN_MASK(x) (~(KVM_PAGES_PER_HPAGE(x) - 1))

static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
{
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 17587f496ec7..3bfc7ee44e51 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2886,7 +2886,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
disallowed_hugepage_adjust(*it.sptep, gfn, it.level,
&pfn, &level);

- base_gfn = gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
+ base_gfn = gfn & KVM_HPAGE_GFN_MASK(it.level);
if (it.level == level)
break;

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 50e268eb8e1a..76ee36f2afd2 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -698,7 +698,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gpa_t addr,
disallowed_hugepage_adjust(*it.sptep, gw->gfn, it.level,
&pfn, &level);

- base_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
+ base_gfn = gw->gfn & KVM_HPAGE_GFN_MASK(it.level);
if (it.level == level)
break;

@@ -751,7 +751,7 @@ FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu,
bool *write_fault_to_shadow_pgtable)
{
int level;
- gfn_t mask = ~(KVM_PAGES_PER_HPAGE(walker->level) - 1);
+ gfn_t mask = KVM_HPAGE_GFN_MASK(walker->level);
bool self_changed = false;

if (!(walker->pte_access & ACC_WRITE_MASK ||
diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c
index 87b7e16911db..c6e914c96641 100644
--- a/arch/x86/kvm/mmu/tdp_iter.c
+++ b/arch/x86/kvm/mmu/tdp_iter.c
@@ -17,7 +17,7 @@ static void tdp_iter_refresh_sptep(struct tdp_iter *iter)

static gfn_t round_gfn_for_level(gfn_t gfn, int level)
{
- return gfn & -KVM_PAGES_PER_HPAGE(level);
+ return gfn & KVM_HPAGE_GFN_MASK(level);
}

/*
--
2.28.0
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