| Message ID | 20220516232138.1783324-6-dmatlack@google.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | KVM: Extend Eager Page Splitting to the shadow MMU | expand |
On Mon, May 16, 2022, David Matlack wrote: > The quadrant is only used when gptes are 4 bytes, but > mmu_alloc_{direct,shadow}_roots() pass in a non-zero quadrant for PAE > page directories regardless. Make this less confusing by only passing in > a non-zero quadrant when it is actually necessary. > > Signed-off-by: David Matlack <dmatlack@google.com> > --- One nit, otherwise Reviewed-by: Sean Christopherson <seanjc@google.com> > arch/x86/kvm/mmu/mmu.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 515e0b33144a..8508c4bfddb5 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -3406,9 +3406,10 @@ static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant, > struct kvm_mmu_page *sp; > > role.level = level; > + role.quadrant = quadrant; > > - if (role.has_4_byte_gpte) > - role.quadrant = quadrant; > + WARN_ON_ONCE(quadrant && !role.has_4_byte_gpte); > + WARN_ON_ONCE(role.direct && role.has_4_byte_gpte); > > sp = kvm_mmu_get_page(vcpu, gfn, role); > ++sp->root_count; > @@ -3444,7 +3445,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) > for (i = 0; i < 4; ++i) { > WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i])); > > - root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), i, > + root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), 0, > PT32_ROOT_LEVEL); > mmu->pae_root[i] = root | PT_PRESENT_MASK | > shadow_me_mask; > @@ -3529,6 +3530,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) > struct kvm_mmu *mmu = vcpu->arch.mmu; > u64 pdptrs[4], pm_mask; > gfn_t root_gfn, root_pgd; > + unsigned int quadrant; > hpa_t root; > unsigned i; Not really your fault, but this manages to use three different type declarations for quadrant. i is a bare "unsigned", quadrant an "unsigned int" here, and then @quadrant in mmu_alloc_root() is an "int". I suspect the "unsigned i" is originated with the "i << (30 - PAGE_SHIFT)" in mmu_alloc_direct_roots(), though even that can't create a negative value. Given that quadrant is tiny and "int i" is a de facto standard for iterator values, my preference would be to opportunisticaly consolidate this to int quadrant, i, r; > int r; > @@ -3614,7 +3616,15 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) > root_gfn = pdptrs[i] >> PAGE_SHIFT; > } > > - root = mmu_alloc_root(vcpu, root_gfn, i, PT32_ROOT_LEVEL); > + /* > + * If shadowing 32-bit non-PAE page tables, each PAE page > + * directory maps one quarter of the guest's non-PAE page > + * directory. Othwerise each PAE page direct shadows one guest > + * PAE page directory so that quadrant should be 0. > + */ > + quadrant = (mmu->cpu_role.base.level == PT32_ROOT_LEVEL) ? i : 0; > + > + root = mmu_alloc_root(vcpu, root_gfn, quadrant, PT32_ROOT_LEVEL); > mmu->pae_root[i] = root | pm_mask; > } > > -- > 2.36.0.550.gb090851708-goog >
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 515e0b33144a..8508c4bfddb5 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3406,9 +3406,10 @@ static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant, struct kvm_mmu_page *sp; role.level = level; + role.quadrant = quadrant; - if (role.has_4_byte_gpte) - role.quadrant = quadrant; + WARN_ON_ONCE(quadrant && !role.has_4_byte_gpte); + WARN_ON_ONCE(role.direct && role.has_4_byte_gpte); sp = kvm_mmu_get_page(vcpu, gfn, role); ++sp->root_count; @@ -3444,7 +3445,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) for (i = 0; i < 4; ++i) { WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i])); - root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), i, + root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), 0, PT32_ROOT_LEVEL); mmu->pae_root[i] = root | PT_PRESENT_MASK | shadow_me_mask; @@ -3529,6 +3530,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) struct kvm_mmu *mmu = vcpu->arch.mmu; u64 pdptrs[4], pm_mask; gfn_t root_gfn, root_pgd; + unsigned int quadrant; hpa_t root; unsigned i; int r; @@ -3614,7 +3616,15 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) root_gfn = pdptrs[i] >> PAGE_SHIFT; } - root = mmu_alloc_root(vcpu, root_gfn, i, PT32_ROOT_LEVEL); + /* + * If shadowing 32-bit non-PAE page tables, each PAE page + * directory maps one quarter of the guest's non-PAE page + * directory. Othwerise each PAE page direct shadows one guest + * PAE page directory so that quadrant should be 0. + */ + quadrant = (mmu->cpu_role.base.level == PT32_ROOT_LEVEL) ? i : 0; + + root = mmu_alloc_root(vcpu, root_gfn, quadrant, PT32_ROOT_LEVEL); mmu->pae_root[i] = root | pm_mask; }
The quadrant is only used when gptes are 4 bytes, but mmu_alloc_{direct,shadow}_roots() pass in a non-zero quadrant for PAE page directories regardless. Make this less confusing by only passing in a non-zero quadrant when it is actually necessary. Signed-off-by: David Matlack <dmatlack@google.com> --- arch/x86/kvm/mmu/mmu.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)