Set the vm's unhandled_msr_exits flag when user space calls the KVM_ENABLE_CAP ioctl with KVM_CAP_UNHANDLED_MSR_EXITS. After kvm fails to handle a guest rdmsr or wrmsr, check this flag and exit to user space with KVM_EXIT_MSR rather than immediately injecting a GP fault.
On reentry into kvm, use the complete_userspace_io callback path to call vmx_complete_userspace_msr. Complete the MSR access if user space was able to handle it successfully, or fail the MSR access and inject a GP fault if user space could not handle the access. Signed-off-by: Peter Hornyack <[email protected]> --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/vmx.c | 74 ++++++++++++++++++++++++++++++++++++++++- arch/x86/kvm/x86.c | 12 +++++++ 3 files changed, 86 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index a6e145b1e271..1b06cea06a8e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -682,6 +682,7 @@ struct kvm_arch { u32 bsp_vcpu_id; u64 disabled_quirks; + bool unhandled_msr_exits; }; struct kvm_vm_stat { diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 27fec385d79d..ba26d382d785 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -32,6 +32,7 @@ #include <linux/slab.h> #include <linux/tboot.h> #include <linux/hrtimer.h> +#include <uapi/linux/kvm.h> #include "kvm_cache_regs.h" #include "x86.h" @@ -5491,6 +5492,53 @@ static void fail_wrmsr(struct kvm_vcpu *vcpu, const struct msr_data *msr) kvm_inject_gp(vcpu, 0); } +/* + * On success, returns 1 so that __vcpu_run() will happen next. On error, + * returns 0. + */ +static int vmx_complete_userspace_msr(struct kvm_vcpu *vcpu) +{ + struct msr_data msr; + + if (vcpu->run->msr.index != vcpu->arch.regs[VCPU_REGS_RCX]) { + pr_debug("msr.index 0x%x changed, does not match ecx 0x%lx\n", + vcpu->run->msr.index, + vcpu->arch.regs[VCPU_REGS_RCX]); + goto err_out; + } + msr.index = vcpu->run->msr.index; + msr.data = vcpu->run->msr.data; + msr.host_initiated = false; + + switch (vcpu->run->msr.direction) { + case KVM_EXIT_MSR_RDMSR: + if (vcpu->run->msr.handled == KVM_EXIT_MSR_HANDLED) + complete_rdmsr(vcpu, &msr); + else + fail_rdmsr(vcpu, &msr); + break; + case KVM_EXIT_MSR_WRMSR: + if (vcpu->run->msr.handled == KVM_EXIT_MSR_HANDLED) + complete_wrmsr(vcpu, &msr); + else + fail_wrmsr(vcpu, &msr); + break; + default: + pr_debug("bad msr.direction %u\n", vcpu->run->msr.direction); + goto err_out; + } + + return 1; +err_out: + vcpu->run->exit_reason = KVM_EXIT_MSR; + vcpu->run->msr.direction = KVM_EXIT_MSR_COMPLETION_FAILED; + return 0; +} + +/* + * Returns 1 if the rdmsr handling is complete; returns 0 if kvm should exit to + * user space to handle this rdmsr. + */ static int handle_rdmsr(struct kvm_vcpu *vcpu) { u32 ecx = vcpu->arch.regs[VCPU_REGS_RCX]; @@ -5499,6 +5547,16 @@ static int handle_rdmsr(struct kvm_vcpu *vcpu) msr_info.index = ecx; msr_info.host_initiated = false; if (vmx_get_msr(vcpu, &msr_info)) { + if (vcpu->kvm->arch.unhandled_msr_exits) { + vcpu->run->exit_reason = KVM_EXIT_MSR; + vcpu->run->msr.direction = KVM_EXIT_MSR_RDMSR; + vcpu->run->msr.index = msr_info.index; + vcpu->run->msr.data = 0; + vcpu->run->msr.handled = 0; + vcpu->arch.complete_userspace_io = + vmx_complete_userspace_msr; + return 0; + } fail_rdmsr(vcpu, &msr_info); return 1; } @@ -5508,6 +5566,10 @@ static int handle_rdmsr(struct kvm_vcpu *vcpu) return 1; } +/* + * Returns 1 if the wrmsr handling is complete; returns 0 if kvm should exit to + * user space to handle this wrmsr. + */ static int handle_wrmsr(struct kvm_vcpu *vcpu) { struct msr_data msr; @@ -5519,6 +5581,16 @@ static int handle_wrmsr(struct kvm_vcpu *vcpu) msr.index = ecx; msr.host_initiated = false; if (kvm_set_msr(vcpu, &msr) != 0) { + if (vcpu->kvm->arch.unhandled_msr_exits) { + vcpu->run->exit_reason = KVM_EXIT_MSR; + vcpu->run->msr.direction = KVM_EXIT_MSR_WRMSR; + vcpu->run->msr.index = msr.index; + vcpu->run->msr.data = msr.data; + vcpu->run->msr.handled = 0; + vcpu->arch.complete_userspace_io = + vmx_complete_userspace_msr; + return 0; + } fail_wrmsr(vcpu, &msr); return 1; } @@ -8163,7 +8235,7 @@ static bool vmx_xsaves_supported(void) static bool vmx_msr_exits_supported(void) { - return false; + return true; } static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 4bbc2a1676c9..5c22f4655741 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2461,6 +2461,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_ENABLE_CAP_VM: case KVM_CAP_DISABLE_QUIRKS: case KVM_CAP_SET_BOOT_CPU_ID: + case KVM_CAP_UNHANDLED_MSR_EXITS: #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT case KVM_CAP_ASSIGN_DEV_IRQ: case KVM_CAP_PCI_2_3: @@ -3568,6 +3569,17 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, kvm->arch.disabled_quirks = cap->args[0]; r = 0; break; + case KVM_CAP_UNHANDLED_MSR_EXITS: + if (kvm_x86_ops->msr_exits_supported()) { + if (cap->args[0]) + kvm->arch.unhandled_msr_exits = true; + else + kvm->arch.unhandled_msr_exits = false; + r = 0; + } else { + r = -EINVAL; + } + break; default: r = -EINVAL; break; -- 2.5.0.276.gf5e568e -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
