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[v2,3/3] KVM: vmx: handle vm-exit for UMWAIT and TPAUSE

Message ID 20190524075637.29496-4-tao3.xu@intel.com (mailing list archive)
State New, archived
Headers show
Series KVM: x86: Enable user wait instructions | expand

Commit Message

Tao Xu May 24, 2019, 7:56 a.m. UTC 
As the latest Intel 64 and IA-32 Architectures Software Developer's
Manual, UMWAIT and TPAUSE instructions cause a VM exit if the
“RDTSC exiting” and “enable user wait and pause” VM-execution controls
are both 1.

This patch is to handle the vm-exit for UMWAIT and TPAUSE as invalid_op.

Co-developed-by: Jingqi Liu <jingqi.liu@intel.com>
Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
Signed-off-by: Tao Xu <tao3.xu@intel.com>
---
 arch/x86/include/uapi/asm/vmx.h |  6 +++++-
 arch/x86/kvm/vmx/vmx.c          | 16 ++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

Comments

Paolo Bonzini May 29, 2019, 1:28 a.m. UTC | #1 
On 24/05/19 09:56, Tao Xu wrote:
> As the latest Intel 64 and IA-32 Architectures Software Developer's
> Manual, UMWAIT and TPAUSE instructions cause a VM exit if the
> “RDTSC exiting” and “enable user wait and pause” VM-execution controls
> are both 1.
> 
> This patch is to handle the vm-exit for UMWAIT and TPAUSE as invalid_op.

KVM never enables RDTSC exiting, so this is not necessary.

Paolo
Tao Xu May 29, 2019, 2:25 a.m. UTC | #2 
On 29/05/2019 09:28, Paolo Bonzini wrote:
> On 24/05/19 09:56, Tao Xu wrote:
>> As the latest Intel 64 and IA-32 Architectures Software Developer's
>> Manual, UMWAIT and TPAUSE instructions cause a VM exit if the
>> “RDTSC exiting” and “enable user wait and pause” VM-execution controls
>> are both 1.
>>
>> This patch is to handle the vm-exit for UMWAIT and TPAUSE as invalid_op.
> 
> KVM never enables RDTSC exiting, so this is not necessary.
> 
> Paolo
> 
OK, but should we just drop this patch?
Or add the VMX_EXIT_REASONS bits of UMWAIT and TPAUSE and handle like 
XSAVES/XRSTORS:
"kvm_skip_emulated_instruction(vcpu);"
"WARN(1, "this should never happen\n");"

Looking forward to your reply.

Tao
Paolo Bonzini May 29, 2019, 2:39 a.m. UTC | #3 
On 29/05/19 04:25, Tao Xu wrote:
>>
> OK, but should we just drop this patch?
> Or add the VMX_EXIT_REASONS bits of UMWAIT and TPAUSE and handle like
> XSAVES/XRSTORS:
> "kvm_skip_emulated_instruction(vcpu);"
> "WARN(1, "this should never happen\n");"

Yes, this sounds good to me.

Paolo
diff mbox series

Patch

diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
index d213ec5c3766..d88d7a68849b 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -85,6 +85,8 @@ 
 #define EXIT_REASON_PML_FULL            62
 #define EXIT_REASON_XSAVES              63
 #define EXIT_REASON_XRSTORS             64
+#define EXIT_REASON_UMWAIT              67
+#define EXIT_REASON_TPAUSE              68
 
 #define VMX_EXIT_REASONS \
 	{ EXIT_REASON_EXCEPTION_NMI,         "EXCEPTION_NMI" }, \
@@ -142,7 +144,9 @@ 
 	{ EXIT_REASON_RDSEED,                "RDSEED" }, \
 	{ EXIT_REASON_PML_FULL,              "PML_FULL" }, \
 	{ EXIT_REASON_XSAVES,                "XSAVES" }, \
-	{ EXIT_REASON_XRSTORS,               "XRSTORS" }
+	{ EXIT_REASON_XRSTORS,               "XRSTORS" }, \
+	{ EXIT_REASON_UMWAIT,                "UMWAIT" }, \
+	{ EXIT_REASON_TPAUSE,                "TPAUSE" }
 
 #define VMX_ABORT_SAVE_GUEST_MSR_FAIL        1
 #define VMX_ABORT_LOAD_HOST_PDPTE_FAIL       2
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 49e107692aee..0743a4ac2b61 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5337,6 +5337,20 @@  static int handle_monitor(struct kvm_vcpu *vcpu)
 	return handle_nop(vcpu);
 }
 
+static int handle_umwait(struct kvm_vcpu *vcpu)
+{
+	printk_once(KERN_WARNING "kvm: Can't use UMWAIT instruction "
+		"when RDTSC exiting VM-execution control is enabled!\n");
+	return handle_invalid_op(vcpu);
+}
+
+static int handle_tpause(struct kvm_vcpu *vcpu)
+{
+	printk_once(KERN_WARNING "kvm: Can't use TPAUSE instruction "
+		"when RDTSC exiting VM-execution control is enabled!\n");
+	return handle_invalid_op(vcpu);
+}
+
 static int handle_invpcid(struct kvm_vcpu *vcpu)
 {
 	u32 vmx_instruction_info;
@@ -5547,6 +5561,8 @@  static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
 	[EXIT_REASON_VMFUNC]		      = handle_vmx_instruction,
 	[EXIT_REASON_PREEMPTION_TIMER]	      = handle_preemption_timer,
 	[EXIT_REASON_ENCLS]		      = handle_encls,
+	[EXIT_REASON_UMWAIT]                  = handle_umwait,
+	[EXIT_REASON_TPAUSE]                  = handle_tpause,
 };
 
 static const int kvm_vmx_max_exit_handlers =