The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: e6f8b6c12f03818baacc5f504fe83fa5e20771d6
Gitweb: https://git.kernel.org/tip/e6f8b6c12f03818baacc5f504fe83fa5e20771d6
Author: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
AuthorDate: Fri, 10 Apr 2020 13:54:02 +02:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Sat, 11 Apr 2020 16:42:41 +02:00
KVM: VMX: Extend VMXs #AC interceptor to handle split lock #AC in guest
Two types of #AC can be generated in Intel CPUs:
1. legacy alignment check #AC
2. split lock #AC
Reflect #AC back into the guest if the guest has legacy alignment checks
enabled or if split lock detection is disabled.
If the #AC is not a legacy one and split lock detection is enabled, then
invoke handle_guest_split_lock() which will either warn and disable split
lock detection for this task or force SIGBUS on it.
[ tglx: Switch it to handle_guest_split_lock() and rename the misnamed
helper function. ]
Suggested-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200410115517.176308876@xxxxxxxxxxxxx
---
arch/x86/kvm/vmx/vmx.c | 37 ++++++++++++++++++++++++++++++++++---
1 file changed, 34 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 8959514..8305097 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4588,6 +4588,26 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
return 1;
}
+/*
+ * If the host has split lock detection disabled, then #AC is
+ * unconditionally injected into the guest, which is the pre split lock
+ * detection behaviour.
+ *
+ * If the host has split lock detection enabled then #AC is
+ * only injected into the guest when:
+ * - Guest CPL == 3 (user mode)
+ * - Guest has #AC detection enabled in CR0
+ * - Guest EFLAGS has AC bit set
+ */
+static inline bool guest_inject_ac(struct kvm_vcpu *vcpu)
+{
+ if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
+ return true;
+
+ return vmx_get_cpl(vcpu) == 3 && kvm_read_cr0_bits(vcpu, X86_CR0_AM) &&
+ (kvm_get_rflags(vcpu) & X86_EFLAGS_AC);
+}
+
static int handle_exception_nmi(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -4653,9 +4673,6 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
return handle_rmode_exception(vcpu, ex_no, error_code);
switch (ex_no) {
- case AC_VECTOR:
- kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);
- return 1;
case DB_VECTOR:
dr6 = vmcs_readl(EXIT_QUALIFICATION);
if (!(vcpu->guest_debug &
@@ -4684,6 +4701,20 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;
kvm_run->debug.arch.exception = ex_no;
break;
+ case AC_VECTOR:
+ if (guest_inject_ac(vcpu)) {
+ kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);
+ return 1;
+ }
+
+ /*
+ * Handle split lock. Depending on detection mode this will
+ * either warn and disable split lock detection for this
+ * task or force SIGBUS on it.
+ */
+ if (handle_guest_split_lock(kvm_rip_read(vcpu)))
+ return 1;
+ fallthrough;
default:
kvm_run->exit_reason = KVM_EXIT_EXCEPTION;
kvm_run->ex.exception = ex_no;
|