Gracefully handle faults on VMXON, e.g. #GP due to VMX being disabled by BIOS, instead of letting the fault crash the system. Now that KVM uses cpufeatures to query support instead of reading MSR_IA32_FEAT_CTL directly, it's possible for a bug in a different subsystem to cause KVM to incorrectly attempt VMXON[*]. Crashing the system is especially annoying if the system is configured such that hardware_enable() will be triggered during boot. Oppurtunistically rename @addr to @vmxon_pointer and use a named param to reference it in the inline assembly. Print 0xdeadbeef in the ultra-"rare" case that reading MSR_IA32_FEAT_CTL also faults. [*] https://lkml.kernel.org/r/20200226231615.13664-1-sean.j.christopherson@xxxxxxxxx Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> --- arch/x86/kvm/vmx/vmx.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 07634caa560d..3aba51d782e2 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -2218,18 +2218,33 @@ static __init int vmx_disabled_by_bios(void) !boot_cpu_has(X86_FEATURE_VMX); } -static void kvm_cpu_vmxon(u64 addr) +static int kvm_cpu_vmxon(u64 vmxon_pointer) { + u64 msr; + cr4_set_bits(X86_CR4_VMXE); intel_pt_handle_vmx(1); - asm volatile ("vmxon %0" : : "m"(addr)); + asm_volatile_goto("1: vmxon %[vmxon_pointer]\n\t" + _ASM_EXTABLE(1b, %l[fault]) + : : [vmxon_pointer] "m"(vmxon_pointer) + : : fault); + return 0; + +fault: + WARN_ONCE(1, "VMXON faulted, MSR_IA32_FEAT_CTL (0x3a) = 0x%llx\n", + rdmsrl_safe(MSR_IA32_FEAT_CTL, &msr) ? 0xdeadbeef : msr); + intel_pt_handle_vmx(0); + cr4_clear_bits(X86_CR4_VMXE); + + return -EFAULT; } static int hardware_enable(void) { int cpu = raw_smp_processor_id(); u64 phys_addr = __pa(per_cpu(vmxarea, cpu)); + int r; if (cr4_read_shadow() & X86_CR4_VMXE) return -EBUSY; @@ -2246,7 +2261,10 @@ static int hardware_enable(void) INIT_LIST_HEAD(&per_cpu(blocked_vcpu_on_cpu, cpu)); spin_lock_init(&per_cpu(blocked_vcpu_on_cpu_lock, cpu)); - kvm_cpu_vmxon(phys_addr); + r = kvm_cpu_vmxon(phys_addr); + if (r) + return r; + if (enable_ept) ept_sync_global(); -- 2.24.1
