kvm: x86: Use fast CR3 switch for nested VMX

Use the fast CR3 switch mechanism to locklessly change the MMU root
page when switching between L1 and L2. The switch from L2 to L1 should
always go through the fast path, while the switch from L1 to L2 should
go through the fast path if L1's CR3/EPTP for L2 hasn't changed
since the last time.

Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3d822a97dfa1660ccf7f5196b322c006a8761066..9b73cfcef917a745093b245b3031f5a030bd2944 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4054,7 +4054,7 @@ static bool fast_cr3_switch(struct kvm_vcpu *vcpu, gpa_t new_cr3,
                        return false;
 
                swap(mmu->root_hpa, mmu->prev_root.hpa);
-               mmu->prev_root.cr3 = kvm_read_cr3(vcpu);
+               mmu->prev_root.cr3 = mmu->get_cr3(vcpu);
 
                if (new_cr3 == prev_cr3 &&
                    VALID_PAGE(mmu->root_hpa) &&
@@ -4091,6 +4091,7 @@ void kvm_mmu_new_cr3(struct kvm_vcpu *vcpu, gpa_t new_cr3)
 {
        __kvm_mmu_new_cr3(vcpu, new_cr3, kvm_mmu_calc_root_page_role(vcpu));
 }
+EXPORT_SYMBOL_GPL(kvm_mmu_new_cr3);
 
 static unsigned long get_cr3(struct kvm_vcpu *vcpu)
 {
@@ -4725,12 +4726,13 @@ kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty)
 }
 
 void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
-                            bool accessed_dirty)
+                            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);
 
+       __kvm_mmu_new_cr3(vcpu, new_eptp, root_page_role);
        context->shadow_root_level = PT64_ROOT_4LEVEL;
 
        context->nx = true;

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 11ab3d62ad65a0f7f5156aae2afa27ccc84092e1..3177127cee96f89635176e550aa10f26646f0b2c 100644 (file)
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -64,7 +64,7 @@ reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
 void kvm_init_mmu(struct kvm_vcpu *vcpu, bool reset_roots);
 void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu);
 void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
-                            bool accessed_dirty);
+                            bool accessed_dirty, gpa_t new_eptp);
 bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu);
 int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
                                u64 fault_address, char *insn, int insn_len);

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cbe31b9d2b81b47053da3fe2d858d5a8fb91289b..c6ea892a610e8aa235a6bf615cc4fbc124b74229 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -10741,11 +10741,11 @@ static int nested_ept_init_mmu_context(struct kvm_vcpu *vcpu)
        if (!valid_ept_address(vcpu, nested_ept_get_cr3(vcpu)))
                return 1;
 
-       kvm_mmu_unload(vcpu);
        kvm_init_shadow_ept_mmu(vcpu,
                        to_vmx(vcpu)->nested.msrs.ept_caps &
                        VMX_EPT_EXECUTE_ONLY_BIT,
-                       nested_ept_ad_enabled(vcpu));
+                       nested_ept_ad_enabled(vcpu),
+                       nested_ept_get_cr3(vcpu));
        vcpu->arch.mmu.set_cr3           = vmx_set_cr3;
        vcpu->arch.mmu.get_cr3           = nested_ept_get_cr3;
        vcpu->arch.mmu.inject_page_fault = nested_ept_inject_page_fault;
@@ -11342,12 +11342,16 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
                                return 1;
                        }
                }
-
-               vcpu->arch.cr3 = cr3;
-               __set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
        }
 
-       kvm_mmu_reset_context(vcpu);
+       if (!nested_ept)
+               kvm_mmu_new_cr3(vcpu, cr3);
+
+       vcpu->arch.cr3 = cr3;
+       __set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
+
+       kvm_init_mmu(vcpu, false);
+
        return 0;
 }
 

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f519eb8d06b142240b511a247a9c7a0b47a3393b..8f461e0ed38219a5e953c4dc9412f877dbafd5f6 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2127,16 +2127,22 @@ static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
 
 static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
 {
+       int ret = -EINTR;
+       int idx = srcu_read_lock(&vcpu->kvm->srcu);
+
        if (kvm_arch_vcpu_runnable(vcpu)) {
                kvm_make_request(KVM_REQ_UNHALT, vcpu);
-               return -EINTR;
+               goto out;
        }
        if (kvm_cpu_has_pending_timer(vcpu))
-               return -EINTR;
+               goto out;
        if (signal_pending(current))
-               return -EINTR;
+               goto out;
 
-       return 0;
+       ret = 0;
+out:
+       srcu_read_unlock(&vcpu->kvm->srcu, idx);
+       return ret;
 }
 
 /*