From 399badf315bd4dd571b4b3b7cf666d9a2af40229 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Fri, 5 Jan 2007 16:36:38 -0800 Subject: [PATCH] [PATCH] KVM: Prevent stale bits in cr0 and cr4 Hardware virtualization implementations allow the guests to freely change some of the bits in cr0 and cr4, but trap when changing the other bits. This is useful to avoid excessive exits due to changing, for example, the ts flag. It also means the kvm's copy of cr0 and cr4 may be stale with respect to these bits. most of the time this doesn't matter as these bits are not very interesting. Other times, however (for example when returning cr0 to userspace), they are, so get the fresh contents of these bits from the guest by means of a new arch operation. Signed-off-by: Avi Kivity Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/kvm/kvm.h | 1 + drivers/kvm/kvm_main.c | 10 ++++++++-- drivers/kvm/svm.c | 5 +++++ drivers/kvm/vmx.c | 10 ++++++++++ 4 files changed, 24 insertions(+), 2 deletions(-) diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h index 32023d1ac2..e8fe1039e3 100644 --- a/drivers/kvm/kvm.h +++ b/drivers/kvm/kvm.h @@ -283,6 +283,7 @@ struct kvm_arch_ops { void (*set_segment)(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg); void (*get_cs_db_l_bits)(struct kvm_vcpu *vcpu, int *db, int *l); + void (*decache_cr0_cr4_guest_bits)(struct kvm_vcpu *vcpu); void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0); void (*set_cr0_no_modeswitch)(struct kvm_vcpu *vcpu, unsigned long cr0); diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c index aca14139a6..bc88c33466 100644 --- a/drivers/kvm/kvm_main.c +++ b/drivers/kvm/kvm_main.c @@ -390,6 +390,7 @@ EXPORT_SYMBOL_GPL(set_cr0); void lmsw(struct kvm_vcpu *vcpu, unsigned long msw) { + kvm_arch_ops->decache_cr0_cr4_guest_bits(vcpu); set_cr0(vcpu, (vcpu->cr0 & ~0x0ful) | (msw & 0x0f)); } EXPORT_SYMBOL_GPL(lmsw); @@ -917,9 +918,10 @@ int emulate_invlpg(struct kvm_vcpu *vcpu, gva_t address) int emulate_clts(struct kvm_vcpu *vcpu) { - unsigned long cr0 = vcpu->cr0; + unsigned long cr0; - cr0 &= ~CR0_TS_MASK; + kvm_arch_ops->decache_cr0_cr4_guest_bits(vcpu); + cr0 = vcpu->cr0 & ~CR0_TS_MASK; kvm_arch_ops->set_cr0(vcpu, cr0); return X86EMUL_CONTINUE; } @@ -1072,6 +1074,7 @@ void realmode_lmsw(struct kvm_vcpu *vcpu, unsigned long msw, unsigned long realmode_get_cr(struct kvm_vcpu *vcpu, int cr) { + kvm_arch_ops->decache_cr0_cr4_guest_bits(vcpu); switch (cr) { case 0: return vcpu->cr0; @@ -1406,6 +1409,7 @@ static int kvm_dev_ioctl_get_sregs(struct kvm *kvm, struct kvm_sregs *sregs) sregs->gdt.limit = dt.limit; sregs->gdt.base = dt.base; + kvm_arch_ops->decache_cr0_cr4_guest_bits(vcpu); sregs->cr0 = vcpu->cr0; sregs->cr2 = vcpu->cr2; sregs->cr3 = vcpu->cr3; @@ -1470,6 +1474,8 @@ static int kvm_dev_ioctl_set_sregs(struct kvm *kvm, struct kvm_sregs *sregs) #endif vcpu->apic_base = sregs->apic_base; + kvm_arch_ops->decache_cr0_cr4_guest_bits(vcpu); + mmu_reset_needed |= vcpu->cr0 != sregs->cr0; kvm_arch_ops->set_cr0_no_modeswitch(vcpu, sregs->cr0); diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c index 855207a9b3..91c7f60ffd 100644 --- a/drivers/kvm/svm.c +++ b/drivers/kvm/svm.c @@ -702,6 +702,10 @@ static void svm_set_gdt(struct kvm_vcpu *vcpu, struct descriptor_table *dt) vcpu->svm->vmcb->save.gdtr.base = dt->base ; } +static void svm_decache_cr0_cr4_guest_bits(struct kvm_vcpu *vcpu) +{ +} + static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) { #ifdef CONFIG_X86_64 @@ -1645,6 +1649,7 @@ static struct kvm_arch_ops svm_arch_ops = { .get_segment = svm_get_segment, .set_segment = svm_set_segment, .get_cs_db_l_bits = svm_get_cs_db_l_bits, + .decache_cr0_cr4_guest_bits = svm_decache_cr0_cr4_guest_bits, .set_cr0 = svm_set_cr0, .set_cr0_no_modeswitch = svm_set_cr0, .set_cr3 = svm_set_cr3, diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c index c55635ddf4..aaa98e3e9c 100644 --- a/drivers/kvm/vmx.c +++ b/drivers/kvm/vmx.c @@ -737,6 +737,15 @@ static void exit_lmode(struct kvm_vcpu *vcpu) #endif +static void vmx_decache_cr0_cr4_guest_bits(struct kvm_vcpu *vcpu) +{ + vcpu->cr0 &= KVM_GUEST_CR0_MASK; + vcpu->cr0 |= vmcs_readl(GUEST_CR0) & ~KVM_GUEST_CR0_MASK; + + vcpu->cr4 &= KVM_GUEST_CR4_MASK; + vcpu->cr4 |= vmcs_readl(GUEST_CR4) & ~KVM_GUEST_CR4_MASK; +} + static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) { if (vcpu->rmode.active && (cr0 & CR0_PE_MASK)) @@ -2002,6 +2011,7 @@ static struct kvm_arch_ops vmx_arch_ops = { .get_segment = vmx_get_segment, .set_segment = vmx_set_segment, .get_cs_db_l_bits = vmx_get_cs_db_l_bits, + .decache_cr0_cr4_guest_bits = vmx_decache_cr0_cr4_guest_bits, .set_cr0 = vmx_set_cr0, .set_cr0_no_modeswitch = vmx_set_cr0_no_modeswitch, .set_cr3 = vmx_set_cr3, -- 2.39.5