From 139f7425fdf54f054463e7524b9f54c41af8407f Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 5 May 2020 09:40:46 -0400 Subject: kvm: x86: Use KVM CPU capabilities to determine CR4 reserved bits Using CPUID data can be useful for the processor compatibility check, but that's it. Using it to compute guest-reserved bits can have both false positives (such as LA57 and UMIP which we are already handling) and false negatives: in particular, with this patch we don't allow anymore a KVM guest to set CR4.PKE when CR4.PKE is clear on the host. Fixes: b9dd21e104bc ("KVM: x86: simplify handling of PKRU") Reported-by: Jim Mattson Tested-by: Jim Mattson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 20 +++++--------------- 1 file changed, 5 insertions(+), 15 deletions(-) (limited to 'arch/x86/kvm/x86.c') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c5835f9cb9ad..8d296e3d0d56 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -926,19 +926,6 @@ EXPORT_SYMBOL_GPL(kvm_set_xcr); __reserved_bits; \ }) -static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c) -{ - u64 reserved_bits = __cr4_reserved_bits(cpu_has, c); - - if (kvm_cpu_cap_has(X86_FEATURE_LA57)) - reserved_bits &= ~X86_CR4_LA57; - - if (kvm_cpu_cap_has(X86_FEATURE_UMIP)) - reserved_bits &= ~X86_CR4_UMIP; - - return reserved_bits; -} - static int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) { if (cr4 & cr4_reserved_bits) @@ -9675,7 +9662,9 @@ int kvm_arch_hardware_setup(void *opaque) if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES)) supported_xss = 0; - cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data); +#define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f) + cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_); +#undef __kvm_cpu_cap_has if (kvm_has_tsc_control) { /* @@ -9707,7 +9696,8 @@ int kvm_arch_check_processor_compat(void *opaque) WARN_ON(!irqs_disabled()); - if (kvm_host_cr4_reserved_bits(c) != cr4_reserved_bits) + if (__cr4_reserved_bits(cpu_has, c) != + __cr4_reserved_bits(cpu_has, &boot_cpu_data)) return -EIO; return ops->check_processor_compatibility(); -- cgit v1.2.3 From 495907ec36def1d28a44e2d1b5a51affe716aacf Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Tue, 5 May 2020 11:47:50 -0400 Subject: KVM: X86: Declare KVM_CAP_SET_GUEST_DEBUG properly KVM_CAP_SET_GUEST_DEBUG should be supported for x86 however it's not declared as supported. My wild guess is that userspaces like QEMU are using "#ifdef KVM_CAP_SET_GUEST_DEBUG" to check for the capability instead, but that could be wrong because the compilation host may not be the runtime host. The userspace might still want to keep the old "#ifdef" though to not break the guest debug on old kernels. Signed-off-by: Peter Xu Message-Id: <20200505154750.126300-1-peterx@redhat.com> [Do the same for PPC and s390. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/kvm/x86.c') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8d296e3d0d56..d786c7d27ce5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3372,6 +3372,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_GET_MSR_FEATURES: case KVM_CAP_MSR_PLATFORM_INFO: case KVM_CAP_EXCEPTION_PAYLOAD: + case KVM_CAP_SET_GUEST_DEBUG: r = 1; break; case KVM_CAP_SYNC_REGS: -- cgit v1.2.3