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Subject[PATCH v1 RESEND 7/9] x86/kvm/nVMX: introduce scache for kvm_init_shadow_ept_mmu
Date
MMU re-initialization is expensive, in particular,
update_permission_bitmask() and update_pkru_bitmask() are.

Cache the data used to setup shadow EPT MMU and avoid full re-init when
it is unchanged.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 14 +++++++++++
arch/x86/kvm/mmu.c | 51 ++++++++++++++++++++++++++++++-----------
2 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6ca7d28d57e9..ab46e9493bd4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -273,8 +273,22 @@ union kvm_mmu_page_role {
};
};

+/*
+ * This structure complements kvm_mmu_page_role caching everything needed for
+ * MMU configuration. If nothing in both these structures changed, MMU
+ * re-configuration can be skipped. @valid bit is set on first usage so we don't
+ * treat all-zero structure as valid data.
+ */
union kvm_mmu_scache {
unsigned int word;
+ struct {
+ unsigned int valid:1;
+ unsigned int execonly:1;
+ unsigned int cr4_pse:1;
+ unsigned int cr4_pke:1;
+ unsigned int cr4_smap:1;
+ unsigned int cr4_smep:1;
+ };
};

union kvm_mmu_role {
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 8d8e6fa75fa3..9e9e12d7cb28 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4708,6 +4708,24 @@ static void paging32E_init_context(struct kvm_vcpu *vcpu,
paging64_init_context_common(vcpu, context, PT32E_ROOT_LEVEL);
}

+static union kvm_mmu_role
+kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu)
+{
+ union kvm_mmu_role role = {0};
+
+ role.base_role.access = ACC_ALL;
+ role.base_role.cr0_wp = is_write_protection(vcpu);
+
+ role.scache.cr4_smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP) != 0;
+ role.scache.cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP) != 0;
+ role.scache.cr4_pse = !!is_pse(vcpu);
+ role.scache.cr4_pke = kvm_read_cr4_bits(vcpu, X86_CR4_PKE) != 0;
+
+ role.scache.valid = 1;
+
+ return role;
+}
+
static union kvm_mmu_page_role
kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu)
{
@@ -4814,16 +4832,18 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);

-static union kvm_mmu_page_role
-kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty)
+static union kvm_mmu_role
+kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
+ bool execonly)
{
- union kvm_mmu_page_role role = vcpu->arch.mmu->mmu_role.base_role;
+ union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu);

- role.level = PT64_ROOT_4LEVEL;
- role.direct = false;
- role.ad_disabled = !accessed_dirty;
- role.guest_mode = true;
- role.access = ACC_ALL;
+ role.base_role.level = PT64_ROOT_4LEVEL;
+ role.base_role.direct = false;
+ role.base_role.ad_disabled = !accessed_dirty;
+ role.base_role.guest_mode = true;
+
+ role.scache.execonly = execonly;

return role;
}
@@ -4832,10 +4852,16 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
bool accessed_dirty, gpa_t new_eptp)
{
struct kvm_mmu *context = vcpu->arch.mmu;
- union kvm_mmu_page_role root_page_role =
- kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty);
+ union kvm_mmu_role new_role =
+ kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty,
+ execonly);
+
+ __kvm_mmu_new_cr3(vcpu, new_eptp, new_role.base_role, false);
+
+ new_role.base_role.word &= mmu_base_role_mask.word;
+ if (new_role.as_u64 == context->mmu_role.as_u64)
+ return;

- __kvm_mmu_new_cr3(vcpu, new_eptp, root_page_role, false);
context->shadow_root_level = PT64_ROOT_4LEVEL;

context->nx = true;
@@ -4847,8 +4873,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
context->update_pte = ept_update_pte;
context->root_level = PT64_ROOT_4LEVEL;
context->direct_map = false;
- context->mmu_role.base_role.word =
- root_page_role.word & mmu_base_role_mask.word;
+ context->mmu_role.as_u64 = new_role.as_u64;
context->get_pdptr = kvm_pdptr_read;

update_permission_bitmask(vcpu, context, true);
--
2.14.4
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