Re: [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs

Re: [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs

[Tony W Wang-oc]

On Sat, Oct 5, 2019, Sean Christopherson wrote:
>Add an entry in struct cpuinfo_x86 to track VMX capabilities and fill
>the capabilities during IA32_FEATURE_CONTROL MSR initialization.
>
>Make the VMX capabilities dependent on X86_INTEL_FEATURE_CONTROL and
>X86_FEATURE_NAMES so as to avoid unnecessary overhead on CPUs that
>can't
>possibly support VMX, or when /proc/cpuinfo is not available.
>
>Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
>---
> arch/x86/Kconfig.cpu                  |  4 ++
> arch/x86/include/asm/processor.h      |  3 ++
> arch/x86/include/asm/vmxfeatures.h    |  5 +++
> arch/x86/kernel/cpu/common.c          |  3 ++
> arch/x86/kernel/cpu/feature_control.c | 59
>+++++++++++++++++++++++++++
> 5 files changed, 74 insertions(+)
>
>diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
>index e78f39adae7b..e7571bd0f515 100644
>--- a/arch/x86/Kconfig.cpu
>+++ b/arch/x86/Kconfig.cpu
>@@ -391,6 +391,10 @@ config X86_FEATURE_CONTROL_MSR
> 	def_bool y
> 	depends on CPU_SUP_INTEL || CPU_SUP_CENTAUR ||
>CPU_SUP_ZHAOXIN
>
>+config X86_VMX_FEATURE_NAMES
>+	def_bool y
>+	depends on X86_FEATURE_CONTROL_MSR &&
>X86_FEATURE_NAMES
>+
> menuconfig PROCESSOR_SELECT
> 	bool "Supported processor vendors" if EXPERT
> 	---help---
>diff --git a/arch/x86/include/asm/processor.h
>b/arch/x86/include/asm/processor.h
>index 4c3f41d7be5f..3b5dc9b1e7c4 100644
>--- a/arch/x86/include/asm/processor.h
>+++ b/arch/x86/include/asm/processor.h
>@@ -84,6 +84,9 @@ struct cpuinfo_x86 {
> #ifdef CONFIG_X86_64
> 	/* Number of 4K pages in DTLB/ITLB combined(in pages): */
> 	int			x86_tlbsize;
>+#endif
>+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
>+	__u32			vmx_capability[NVMXINTS];
> #endif
> 	__u8			x86_virt_bits;
> 	__u8			x86_phys_bits;
>diff --git a/arch/x86/include/asm/vmxfeatures.h
>b/arch/x86/include/asm/vmxfeatures.h
>index ab82e3643d0c..d33ea1c165fd 100644
>--- a/arch/x86/include/asm/vmxfeatures.h
>+++ b/arch/x86/include/asm/vmxfeatures.h
>@@ -2,6 +2,11 @@
> #ifndef _ASM_X86_VMXFEATURES_H
> #define _ASM_X86_VMXFEATURES_H
>
>+/*
>+ * Defines VMX CPU feature bits
>+ */
>+#define NVMXINTS			3 /* N 32-bit words worth of info */
>+
> /*
>  * Note: If the comment begins with a quoted string, that string is used
>  * in /proc/cpuinfo instead of the macro name.  If the string is "",
>diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
>index 9ae7d1bcd4f4..33537556dac6 100644
>--- a/arch/x86/kernel/cpu/common.c
>+++ b/arch/x86/kernel/cpu/common.c
>@@ -1421,6 +1421,9 @@ static void identify_cpu(struct cpuinfo_x86 *c)
> #endif
> 	c->x86_cache_alignment = c->x86_clflush_size;
> 	memset(&c->x86_capability, 0, sizeof(c->x86_capability));
>+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
>+	memset(&c->vmx_capability, 0, sizeof(c->vmx_capability));
>+#endif
>
> 	generic_identify(c);
>
>diff --git a/arch/x86/kernel/cpu/feature_control.c
>b/arch/x86/kernel/cpu/feature_control.c
>index 74c76159a046..43eb65e8cd18 100644
>--- a/arch/x86/kernel/cpu/feature_control.c
>+++ b/arch/x86/kernel/cpu/feature_control.c
>@@ -4,6 +4,61 @@
> #include <asm/cpufeature.h>
> #include <asm/msr-index.h>
> #include <asm/processor.h>
>+#include <asm/vmx.h>
>+
>+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
>+enum vmx_feature_leafs {
>+	MISC_FEATURES = 0,
>+	PRIMARY_PROC_CONTROLS,
>+	SECONDARY_PROC_CONTROLS,
>+	NR_VMX_FEATURE_WORDS,
>+};
>+
>+#define EPT_BIT(x) BIT(VMX_FEATURE_##x & 0x1f)
>+
>+static void init_vmx_capabilities(struct cpuinfo_x86 *c)
>+{
>+	u32 supported, funcs, ept, vpid, ign;
>+
>+	BUILD_BUG_ON(NVMXINTS != NR_VMX_FEATURE_WORDS);
>+
>+	/*
>+	 * The high bits contain the allowed-1 settings, i.e. features that can
>+	 * be turned on.  The low bits contain the allowed-0 settings, i.e.
>+	 * features that can be turned off.  Ignore the allowed-0 settings,
>+	 * if a feature can be turned on then it's supported.
>+	 */
>+	rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);
>+	rdmsr_safe(MSR_IA32_VMX_VMFUNC, &ign, &funcs);
>+
>+	/*
>+	 * Except for EPT+VPID, which enumerates support for both in a single
>+	 * MSR, low for EPT, high for VPID.
>+	 */
>+	rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, &ept, &vpid);
>+
>+	/* Pin, EPT, VPID and VM-Func are merged into a single word. */
>+	WARN_ON_ONCE(supported >> 16);
>+	WARN_ON_ONCE(funcs >> 4);
>+	c->vmx_capability[MISC_FEATURES] = (supported & 0xffff) |
>+					   ((vpid & 0x1) << 24) |
>+					   ((funcs & 0xf) << 28);
>+
>+	/* EPT bits are scattered and must be manually handled. */
>+	if (ept & VMX_EPT_EXECUTE_ONLY_BIT)
>+		c->vmx_capability[MISC_FEATURES] |=
>EPT_BIT(EPT_EXECUTE_ONLY);
>+	if (ept & VMX_EPT_1GB_PAGE_BIT)

Typo? Should be: if (ept & VMX_EPT_AD_BIT)

TonyWWang-oc

>+		c->vmx_capability[MISC_FEATURES] |= EPT_BIT(EPT_AD);
>+	if (ept & VMX_EPT_1GB_PAGE_BIT)
>+		c->vmx_capability[MISC_FEATURES] |= EPT_BIT(EPT_1GB);
>+
>+	rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, ign, supported);
>+	c->vmx_capability[PRIMARY_PROC_CONTROLS] = supported;
>+
>+	rdmsr_safe(MSR_IA32_VMX_PROCBASED_CTLS2, &ign, &supported);
>+	c->vmx_capability[SECONDARY_PROC_CONTROLS] = supported;
>+}
>+#endif /* CONFIG_X86_VMX_FEATURE_NAMES */
>
> void init_feature_control_msr(struct cpuinfo_x86 *c)
> {
>@@ -43,5 +98,9 @@ void init_feature_control_msr(struct cpuinfo_x86 *c)
> 		pr_err_once("x86/cpu: VMX disabled by BIOS (TXT %s)\n",
> 			    tboot ? "enabled" : "disabled");
> 		clear_cpu_cap(c, X86_FEATURE_VMX);
>+	} else {
>+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
>+		init_vmx_capabilities(c);
>+#endif
> 	}
> }
>--
>2.22.0

Re: [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs

[Paolo Bonzini]

On 07/10/19 21:54, Sean Christopherson wrote:
>> For QEMU, we're defining a feature as supported if a feature can be
>> turned both on and off.  Since msr_low and msr_high can be defined
>> respectively as must-be-one and can-be-one, the features become
>> "msr_high & ~msr_low".
> 
> That makes sense for Qemu, but I don't think it's appropriate for this
> type of reporting.  E.g. if EPT and Unrestricted Guest are must-be-one on
> a hypothetical (virtual) CPU, it'd be odd to not list them as a supported
> feature.
> 
> For actual hardware (well, Intel hardware), as proposed it's a moot point.
> The only features that are must-be-one (even without "true" MSRs) and are
> documented in the SDM are CR3_LOAD_EXITING, CR3_STORE_EXITING,
> SAVE_DEBUG_CONTROLS, and LOAD_DEBUG_CONTROLS, none of which are reported
> in /proc/cpuinfo.
> 
>> Also, shouldn't this use the "true" feature availability MSRs if available?
> 
> Only if incorporating the "& ~msr_low" can-be-one logic.  If a feature is
> considered supported if it must-be-one or can-be-one then the true MSR and
> vanilla MSR will yield the same feature set.

Ok, that all makes sense.

Paolo

Re: [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs

[Sean Christopherson]

On Mon, Oct 07, 2019 at 07:11:24PM +0200, Paolo Bonzini wrote:
> On 04/10/19 23:56, Sean Christopherson wrote:
> > +	/*
> > +	 * The high bits contain the allowed-1 settings, i.e. features that can
> > +	 * be turned on.  The low bits contain the allowed-0 settings, i.e.
> > +	 * features that can be turned off.  Ignore the allowed-0 settings,
> > +	 * if a feature can be turned on then it's supported.
> > +	 */
> > +	rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);
> 
> For QEMU, we're defining a feature as supported if a feature can be
> turned both on and off.  Since msr_low and msr_high can be defined
> respectively as must-be-one and can-be-one, the features become
> "msr_high & ~msr_low".

That makes sense for Qemu, but I don't think it's appropriate for this
type of reporting.  E.g. if EPT and Unrestricted Guest are must-be-one on
a hypothetical (virtual) CPU, it'd be odd to not list them as a supported
feature.

For actual hardware (well, Intel hardware), as proposed it's a moot point.
The only features that are must-be-one (even without "true" MSRs) and are
documented in the SDM are CR3_LOAD_EXITING, CR3_STORE_EXITING,
SAVE_DEBUG_CONTROLS, and LOAD_DEBUG_CONTROLS, none of which are reported
in /proc/cpuinfo.

> Also, shouldn't this use the "true" feature availability MSRs if available?

Only if incorporating the "& ~msr_low" can-be-one logic.  If a feature is
considered supported if it must-be-one or can-be-one then the true MSR and
vanilla MSR will yield the same feature set.

> 
> Paolo

Re: [PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs

[Paolo Bonzini]

On 04/10/19 23:56, Sean Christopherson wrote:
> +	/*
> +	 * The high bits contain the allowed-1 settings, i.e. features that can
> +	 * be turned on.  The low bits contain the allowed-0 settings, i.e.
> +	 * features that can be turned off.  Ignore the allowed-0 settings,
> +	 * if a feature can be turned on then it's supported.
> +	 */
> +	rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);

For QEMU, we're defining a feature as supported if a feature can be
turned both on and off.  Since msr_low and msr_high can be defined
respectively as must-be-one and can-be-one, the features become
"msr_high & ~msr_low".

Also, shouldn't this use the "true" feature availability MSRs if available?

Paolo

[PATCH 10/16] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs

[Sean Christopherson]

Add an entry in struct cpuinfo_x86 to track VMX capabilities and fill
the capabilities during IA32_FEATURE_CONTROL MSR initialization.

Make the VMX capabilities dependent on X86_INTEL_FEATURE_CONTROL and
X86_FEATURE_NAMES so as to avoid unnecessary overhead on CPUs that can't
possibly support VMX, or when /proc/cpuinfo is not available.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/Kconfig.cpu                  |  4 ++
 arch/x86/include/asm/processor.h      |  3 ++
 arch/x86/include/asm/vmxfeatures.h    |  5 +++
 arch/x86/kernel/cpu/common.c          |  3 ++
 arch/x86/kernel/cpu/feature_control.c | 59 +++++++++++++++++++++++++++
 5 files changed, 74 insertions(+)

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index e78f39adae7b..e7571bd0f515 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -391,6 +391,10 @@ config X86_FEATURE_CONTROL_MSR
 	def_bool y
 	depends on CPU_SUP_INTEL || CPU_SUP_CENTAUR || CPU_SUP_ZHAOXIN
 
+config X86_VMX_FEATURE_NAMES
+	def_bool y
+	depends on X86_FEATURE_CONTROL_MSR && X86_FEATURE_NAMES
+
 menuconfig PROCESSOR_SELECT
 	bool "Supported processor vendors" if EXPERT
 	---help---
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 4c3f41d7be5f..3b5dc9b1e7c4 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -84,6 +84,9 @@ struct cpuinfo_x86 {
 #ifdef CONFIG_X86_64
 	/* Number of 4K pages in DTLB/ITLB combined(in pages): */
 	int			x86_tlbsize;
+#endif
+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
+	__u32			vmx_capability[NVMXINTS];
 #endif
 	__u8			x86_virt_bits;
 	__u8			x86_phys_bits;
diff --git a/arch/x86/include/asm/vmxfeatures.h b/arch/x86/include/asm/vmxfeatures.h
index ab82e3643d0c..d33ea1c165fd 100644
--- a/arch/x86/include/asm/vmxfeatures.h
+++ b/arch/x86/include/asm/vmxfeatures.h
@@ -2,6 +2,11 @@
 #ifndef _ASM_X86_VMXFEATURES_H
 #define _ASM_X86_VMXFEATURES_H
 
+/*
+ * Defines VMX CPU feature bits
+ */
+#define NVMXINTS			3 /* N 32-bit words worth of info */
+
 /*
  * Note: If the comment begins with a quoted string, that string is used
  * in /proc/cpuinfo instead of the macro name.  If the string is "",
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9ae7d1bcd4f4..33537556dac6 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1421,6 +1421,9 @@ static void identify_cpu(struct cpuinfo_x86 *c)
 #endif
 	c->x86_cache_alignment = c->x86_clflush_size;
 	memset(&c->x86_capability, 0, sizeof(c->x86_capability));
+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
+	memset(&c->vmx_capability, 0, sizeof(c->vmx_capability));
+#endif
 
 	generic_identify(c);
 
diff --git a/arch/x86/kernel/cpu/feature_control.c b/arch/x86/kernel/cpu/feature_control.c
index 74c76159a046..43eb65e8cd18 100644
--- a/arch/x86/kernel/cpu/feature_control.c
+++ b/arch/x86/kernel/cpu/feature_control.c
@@ -4,6 +4,61 @@
 #include <asm/cpufeature.h>
 #include <asm/msr-index.h>
 #include <asm/processor.h>
+#include <asm/vmx.h>
+
+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
+enum vmx_feature_leafs {
+	MISC_FEATURES = 0,
+	PRIMARY_PROC_CONTROLS,
+	SECONDARY_PROC_CONTROLS,
+	NR_VMX_FEATURE_WORDS,
+};
+
+#define EPT_BIT(x) BIT(VMX_FEATURE_##x & 0x1f)
+
+static void init_vmx_capabilities(struct cpuinfo_x86 *c)
+{
+	u32 supported, funcs, ept, vpid, ign;
+
+	BUILD_BUG_ON(NVMXINTS != NR_VMX_FEATURE_WORDS);
+
+	/*
+	 * The high bits contain the allowed-1 settings, i.e. features that can
+	 * be turned on.  The low bits contain the allowed-0 settings, i.e.
+	 * features that can be turned off.  Ignore the allowed-0 settings,
+	 * if a feature can be turned on then it's supported.
+	 */
+	rdmsr(MSR_IA32_VMX_PINBASED_CTLS, ign, supported);
+	rdmsr_safe(MSR_IA32_VMX_VMFUNC, &ign, &funcs);
+
+	/*
+	 * Except for EPT+VPID, which enumerates support for both in a single
+	 * MSR, low for EPT, high for VPID.
+	 */
+	rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP, &ept, &vpid);
+
+	/* Pin, EPT, VPID and VM-Func are merged into a single word. */
+	WARN_ON_ONCE(supported >> 16);
+	WARN_ON_ONCE(funcs >> 4);
+	c->vmx_capability[MISC_FEATURES] = (supported & 0xffff) |
+					   ((vpid & 0x1) << 24) |
+					   ((funcs & 0xf) << 28);
+
+	/* EPT bits are scattered and must be manually handled. */
+	if (ept & VMX_EPT_EXECUTE_ONLY_BIT)
+		c->vmx_capability[MISC_FEATURES] |= EPT_BIT(EPT_EXECUTE_ONLY);
+	if (ept & VMX_EPT_1GB_PAGE_BIT)
+		c->vmx_capability[MISC_FEATURES] |= EPT_BIT(EPT_AD);
+	if (ept & VMX_EPT_1GB_PAGE_BIT)
+		c->vmx_capability[MISC_FEATURES] |= EPT_BIT(EPT_1GB);
+
+	rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, ign, supported);
+	c->vmx_capability[PRIMARY_PROC_CONTROLS] = supported;
+
+	rdmsr_safe(MSR_IA32_VMX_PROCBASED_CTLS2, &ign, &supported);
+	c->vmx_capability[SECONDARY_PROC_CONTROLS] = supported;
+}
+#endif /* CONFIG_X86_VMX_FEATURE_NAMES */
 
 void init_feature_control_msr(struct cpuinfo_x86 *c)
 {
@@ -43,5 +98,9 @@ void init_feature_control_msr(struct cpuinfo_x86 *c)
 		pr_err_once("x86/cpu: VMX disabled by BIOS (TXT %s)\n",
 			    tboot ? "enabled" : "disabled");
 		clear_cpu_cap(c, X86_FEATURE_VMX);
+	} else {
+#ifdef CONFIG_X86_VMX_FEATURE_NAMES
+		init_vmx_capabilities(c);
+#endif
 	}
 }
-- 
2.22.0