KVM: VMX: Gracefully handle faults on VMXON (4f6ea0a8) · Commits · 戴 / test

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@intel.com Signed-off-by:

Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200321193751.24985-4-sean.j.christopherson@intel.com> Reviewed-by:

Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

+21 −3

Original line number	Diff line number	Diff line
		@@ -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();

Admin message