Avi Kivity wrote:
> On 07/24/2009 12:41 PM, Jan Kiszka wrote:
>> I vaguely recall that someone promised to add a feature reporting
>> facility for all those nice things, modern VM-extensions may or may not
>> support (something like or even an extension of /proc/cpuinfo). What is
>> the state of this plan? Would be specifically interesting for Intel CPUs
>> as there seem to be many of them out there with restrictions for special
>> use cases - like real-time.
>>
>
> Newer kernels do report some vmx features (like flexpriority) in
> /proc/cpuinfo but not all.
>
Ah, nice. Then we just need this?
------------>
From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Subject: [PATCH] x86: Report VMX feature vwbinvd
Not all VMX-capable CPUs support guest exists on wbinvd execution. If
this is not supported, the instruction will run natively on behalf of
the guest. This can cause multi-millisecond latencies to the host which
is very problematic in real-time scenarios.
Report the wbinvd trapping feature along with other VMX feature flags,
calling it 'vwbinvd' ('virtual wbinvd').
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
arch/x86/include/asm/cpufeature.h | 1 +
arch/x86/kernel/cpu/intel.c | 4 ++++
2 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 4a28d22..8647524 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -165,6 +165,7 @@
#define X86_FEATURE_FLEXPRIORITY (8*32+ 2) /* Intel FlexPriority */
#define X86_FEATURE_EPT (8*32+ 3) /* Intel Extended Page Table */
#define X86_FEATURE_VPID (8*32+ 4) /* Intel Virtual Processor ID */
+#define X86_FEATURE_VWBINVD (8*32+ 5) /* Guest Exiting on WBINVD */
#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 3260ab0..2d921b0 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -297,6 +297,7 @@ static void __cpuinit detect_vmx_virtcap(struct cpuinfo_x86 *c)
#define X86_VMX_FEATURE_PROC_CTLS2_VIRT_APIC 0x00000001
#define X86_VMX_FEATURE_PROC_CTLS2_EPT 0x00000002
#define X86_VMX_FEATURE_PROC_CTLS2_VPID 0x00000020
+#define X86_VMX_FEATURE_PROC_CTLS2_VWBINVD 0x00000040
u32 vmx_msr_low, vmx_msr_high, msr_ctl, msr_ctl2;
@@ -305,6 +306,7 @@ static void __cpuinit detect_vmx_virtcap(struct cpuinfo_x86 *c)
clear_cpu_cap(c, X86_FEATURE_FLEXPRIORITY);
clear_cpu_cap(c, X86_FEATURE_EPT);
clear_cpu_cap(c, X86_FEATURE_VPID);
+ clear_cpu_cap(c, X86_FEATURE_VWBINVD);
rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, vmx_msr_low, vmx_msr_high);
msr_ctl = vmx_msr_high | vmx_msr_low;
@@ -323,6 +325,8 @@ static void __cpuinit detect_vmx_virtcap(struct cpuinfo_x86 *c)
set_cpu_cap(c, X86_FEATURE_EPT);
if (msr_ctl2 & X86_VMX_FEATURE_PROC_CTLS2_VPID)
set_cpu_cap(c, X86_FEATURE_VPID);
+ if (msr_ctl2 & X86_VMX_FEATURE_PROC_CTLS2_VWBINVD)
+ set_cpu_cap(c, X86_FEATURE_VWBINVD);
}
}
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