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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	"Kenneth R. Crudup" <kenny@panix.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Fenghua Yu <fenghua.yu@intel.com>, Nadav Amit <namit@vmware.com>,
	Thomas Hellstrom <thellstrom@vmware.com>,
	Tony Luck <tony.luck@intel.com>
Subject: [patch 3/3] KVM: VMX: Extend VMXs #AC interceptor to handle split lock #AC in guest
Date: Fri, 10 Apr 2020 13:54:02 +0200
Message-ID: <20200410115517.176308876@linutronix.de> (raw)
In-Reply-To: <20200410115359.242241855@linutronix.de>

From: Xiaoyao Li <xiaoyao.li@intel.com>

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 renamed the misnomed
  	helper function ]

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kvm/vmx/vmx.c |   37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4592,6 +4592,26 @@ static int handle_machine_check(struct k
 	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);
@@ -4657,9 +4677,6 @@ static int handle_exception_nmi(struct k
 		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 &
@@ -4688,6 +4705,20 @@ static int handle_exception_nmi(struct k
 		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;


  parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-10 11:53 [patch 0/3] x86/kvm: Basic split lock #AC handling Thomas Gleixner
2020-04-10 11:54 ` [patch 1/3] x86/split_lock: Provide handle_guest_split_lock() Thomas Gleixner
2020-04-11 16:04   ` [tip: x86/urgent] " tip-bot2 for Thomas Gleixner
2020-04-10 11:54 ` [patch 2/3] KVM: x86: Emulate split-lock access as a write in emulator Thomas Gleixner
2020-04-11 16:04   ` [tip: x86/urgent] " tip-bot2 for Xiaoyao Li
2020-04-10 11:54 ` Thomas Gleixner [this message]
2020-04-11 16:04   ` [tip: x86/urgent] KVM: VMX: Extend VMXs #AC interceptor to handle split lock #AC in guest tip-bot2 for Xiaoyao Li
2020-04-10 15:15 ` [patch 0/3] x86/kvm: Basic split lock #AC handling Paolo Bonzini
2020-04-10 19:02 ` Sean Christopherson
2020-04-14  7:38   ` Thomas Gleixner

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