From: Avi Kivity A side effect of using vm86 mode to simulate real mode is that we mangle the segment registers on mode switching. The new set_cr0_no_modeswitch() accessor avoids the mangling when the restore is due to loading the virtual machine from a file. Signed-off-by: Avi Kivity Signed-off-by: Andrew Morton --- drivers/kvm/kvm.h | 4 ++-- drivers/kvm/kvm_main.c | 7 +------ drivers/kvm/vmx.c | 16 ++++++++++++++-- 3 files changed, 17 insertions(+), 10 deletions(-) diff -puN drivers/kvm/kvm.h~kvm-add-a-set_cr0_no_modeswitch-arch-accessor drivers/kvm/kvm.h --- a/drivers/kvm/kvm.h~kvm-add-a-set_cr0_no_modeswitch-arch-accessor +++ a/drivers/kvm/kvm.h @@ -271,6 +271,8 @@ struct kvm_arch_ops { struct kvm_segment *var, int seg); void (*get_cs_db_l_bits)(struct kvm_vcpu *vcpu, int *db, int *l); void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0); + void (*set_cr0_no_modeswitch)(struct kvm_vcpu *vcpu, + unsigned long cr0); void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3); void (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4); void (*set_efer)(struct kvm_vcpu *vcpu, u64 efer); @@ -292,8 +294,6 @@ struct kvm_arch_ops { int (*run)(struct kvm_vcpu *vcpu, struct kvm_run *run); int (*vcpu_setup)(struct kvm_vcpu *vcpu); void (*skip_emulated_instruction)(struct kvm_vcpu *vcpu); - - void (*update_exception_bitmap)(struct kvm_vcpu *vcpu); /* hack */ }; extern struct kvm_stat kvm_stat; diff -puN drivers/kvm/kvm_main.c~kvm-add-a-set_cr0_no_modeswitch-arch-accessor drivers/kvm/kvm_main.c --- a/drivers/kvm/kvm_main.c~kvm-add-a-set_cr0_no_modeswitch-arch-accessor +++ a/drivers/kvm/kvm_main.c @@ -1529,12 +1529,7 @@ static int kvm_dev_ioctl_set_sregs(struc vcpu->apic_base = sregs->apic_base; mmu_reset_needed |= vcpu->cr0 != sregs->cr0; - vcpu->rmode.active = ((sregs->cr0 & CR0_PE_MASK) == 0); - kvm_arch_ops->update_exception_bitmap(vcpu); - vmcs_writel(CR0_READ_SHADOW, sregs->cr0); - vmcs_writel(GUEST_CR0, - (sregs->cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON); - vcpu->cr0 = sregs->cr0; + kvm_arch_ops->set_cr0_no_modeswitch(vcpu, sregs->cr0); mmu_reset_needed |= vcpu->cr4 != sregs->cr4; kvm_arch_ops->set_cr4(vcpu, sregs->cr4); diff -puN drivers/kvm/vmx.c~kvm-add-a-set_cr0_no_modeswitch-arch-accessor drivers/kvm/vmx.c --- a/drivers/kvm/vmx.c~kvm-add-a-set_cr0_no_modeswitch-arch-accessor +++ a/drivers/kvm/vmx.c @@ -607,6 +607,19 @@ static void vmx_set_cr0(struct kvm_vcpu vcpu->cr0 = cr0; } +/* + * Used when restoring the VM to avoid corrupting segment registers + */ +static void vmx_set_cr0_no_modeswitch(struct kvm_vcpu *vcpu, unsigned long cr0) +{ + vcpu->rmode.active = ((cr0 & CR0_PE_MASK) == 0); + update_exception_bitmap(vcpu); + vmcs_writel(CR0_READ_SHADOW, cr0); + vmcs_writel(GUEST_CR0, + (cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON); + vcpu->cr0 = cr0; +} + static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) { vmcs_writel(GUEST_CR3, cr3); @@ -1740,6 +1753,7 @@ static struct kvm_arch_ops vmx_arch_ops .set_segment = vmx_set_segment, .get_cs_db_l_bits = vmx_get_cs_db_l_bits, .set_cr0 = vmx_set_cr0, + .set_cr0_no_modeswitch = vmx_set_cr0_no_modeswitch, .set_cr3 = vmx_set_cr3, .set_cr4 = vmx_set_cr4, .set_efer = vmx_set_efer, @@ -1760,8 +1774,6 @@ static struct kvm_arch_ops vmx_arch_ops .run = vmx_vcpu_run, .skip_emulated_instruction = skip_emulated_instruction, .vcpu_setup = vmx_vcpu_setup, - - .update_exception_bitmap = update_exception_bitmap, }; static int __init vmx_init(void) _