From: Xin Li <[email protected]>
Add IA32_VMX_BASIC MSR bitfield shift macros and use them to define VMX
basic information bitfields.
Add VMX_BASIC_FEATURES and VMX_BASIC_RESERVED_BITS to form a valid bitmask
of IA32_VMX_BASIC MSR. As a result, to add a new VMX basic feature bit,
just change the 2 new macros in the header file.
Also replace hardcoded VMX basic numbers with the new VMX basic macros.
Tested-by: Shan Kang <[email protected]>
Signed-off-by: Xin Li <[email protected]>
---
arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
arch/x86/kvm/vmx/nested.c | 10 +++------
arch/x86/kvm/vmx/vmx.c | 2 +-
tools/arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
4 files changed, 52 insertions(+), 22 deletions(-)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 1d111350197f..4607448ff805 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1084,13 +1084,30 @@
#define MSR_IA32_VMX_PROCBASED_CTLS3 0x00000492
/* VMX_BASIC bits and bitmasks */
-#define VMX_BASIC_VMCS_SIZE_SHIFT 32
-#define VMX_BASIC_TRUE_CTLS (1ULL << 55)
-#define VMX_BASIC_64 0x0001000000000000LLU
-#define VMX_BASIC_MEM_TYPE_SHIFT 50
-#define VMX_BASIC_MEM_TYPE_MASK 0x003c000000000000LLU
-#define VMX_BASIC_MEM_TYPE_WB 6LLU
-#define VMX_BASIC_INOUT 0x0040000000000000LLU
+#define VMX_BASIC_VMCS_SIZE_SHIFT 32
+#define VMX_BASIC_ALWAYS_0 BIT_ULL(31)
+#define VMX_BASIC_RESERVED_RANGE_1 GENMASK_ULL(47, 45)
+#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT 48
+#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT)
+#define VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT 49
+#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT)
+#define VMX_BASIC_MEM_TYPE_SHIFT 50
+#define VMX_BASIC_MEM_TYPE_WB 6LLU
+#define VMX_BASIC_INOUT_SHIFT 54
+#define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT)
+#define VMX_BASIC_TRUE_CTLS_SHIFT 55
+#define VMX_BASIC_TRUE_CTLS BIT_ULL(VMX_BASIC_TRUE_CTLS_SHIFT)
+#define VMX_BASIC_RESERVED_RANGE_2 GENMASK_ULL(63, 56)
+
+#define VMX_BASIC_FEATURES \
+ (VMX_BASIC_DUAL_MONITOR_TREATMENT | \
+ VMX_BASIC_INOUT | \
+ VMX_BASIC_TRUE_CTLS)
+
+#define VMX_BASIC_RESERVED_BITS \
+ (VMX_BASIC_ALWAYS_0 | \
+ VMX_BASIC_RESERVED_RANGE_1 | \
+ VMX_BASIC_RESERVED_RANGE_2)
/* Resctrl MSRs: */
/* - Intel: */
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c5ec0ef51ff7..5280ba944c87 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1203,21 +1203,17 @@ static bool is_bitwise_subset(u64 superset, u64 subset, u64 mask)
static int vmx_restore_vmx_basic(struct vcpu_vmx *vmx, u64 data)
{
- const u64 feature_and_reserved =
- /* feature (except bit 48; see below) */
- BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |
- /* reserved */
- BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56);
u64 vmx_basic = vmcs_config.nested.basic;
- if (!is_bitwise_subset(vmx_basic, data, feature_and_reserved))
+ if (!is_bitwise_subset(vmx_basic, data,
+ VMX_BASIC_FEATURES | VMX_BASIC_RESERVED_BITS))
return -EINVAL;
/*
* KVM does not emulate a version of VMX that constrains physical
* addresses of VMX structures (e.g. VMCS) to 32-bits.
*/
- if (data & BIT_ULL(48))
+ if (data & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
return -EINVAL;
if (vmx_basic_vmcs_revision_id(vmx_basic) !=
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 72e3943f3693..f597243d6a72 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2701,7 +2701,7 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
#ifdef CONFIG_X86_64
/* IA-32 SDM Vol 3B: 64-bit CPUs always have VMX_BASIC_MSR[48]==0. */
- if (vmx_msr_high & (1u<<16))
+ if (vmx_msr_high & (1u << (VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT - 32)))
return -EIO;
#endif
diff --git a/tools/arch/x86/include/asm/msr-index.h b/tools/arch/x86/include/asm/msr-index.h
index 1d111350197f..4607448ff805 100644
--- a/tools/arch/x86/include/asm/msr-index.h
+++ b/tools/arch/x86/include/asm/msr-index.h
@@ -1084,13 +1084,30 @@
#define MSR_IA32_VMX_PROCBASED_CTLS3 0x00000492
/* VMX_BASIC bits and bitmasks */
-#define VMX_BASIC_VMCS_SIZE_SHIFT 32
-#define VMX_BASIC_TRUE_CTLS (1ULL << 55)
-#define VMX_BASIC_64 0x0001000000000000LLU
-#define VMX_BASIC_MEM_TYPE_SHIFT 50
-#define VMX_BASIC_MEM_TYPE_MASK 0x003c000000000000LLU
-#define VMX_BASIC_MEM_TYPE_WB 6LLU
-#define VMX_BASIC_INOUT 0x0040000000000000LLU
+#define VMX_BASIC_VMCS_SIZE_SHIFT 32
+#define VMX_BASIC_ALWAYS_0 BIT_ULL(31)
+#define VMX_BASIC_RESERVED_RANGE_1 GENMASK_ULL(47, 45)
+#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT 48
+#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT)
+#define VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT 49
+#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT)
+#define VMX_BASIC_MEM_TYPE_SHIFT 50
+#define VMX_BASIC_MEM_TYPE_WB 6LLU
+#define VMX_BASIC_INOUT_SHIFT 54
+#define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT)
+#define VMX_BASIC_TRUE_CTLS_SHIFT 55
+#define VMX_BASIC_TRUE_CTLS BIT_ULL(VMX_BASIC_TRUE_CTLS_SHIFT)
+#define VMX_BASIC_RESERVED_RANGE_2 GENMASK_ULL(63, 56)
+
+#define VMX_BASIC_FEATURES \
+ (VMX_BASIC_DUAL_MONITOR_TREATMENT | \
+ VMX_BASIC_INOUT | \
+ VMX_BASIC_TRUE_CTLS)
+
+#define VMX_BASIC_RESERVED_BITS \
+ (VMX_BASIC_ALWAYS_0 | \
+ VMX_BASIC_RESERVED_RANGE_1 | \
+ VMX_BASIC_RESERVED_RANGE_2)
/* Resctrl MSRs: */
/* - Intel: */
--
2.40.1
On Wed, Sep 27, 2023, Xin Li (Intel) wrote:
> From: Xin Li <[email protected]>
>
> Add IA32_VMX_BASIC MSR bitfield shift macros and use them to define VMX
> basic information bitfields.
Why? Unless something actually uses the shift independently, just define the
BIT_ULL(...) straightaway.
> Add VMX_BASIC_FEATURES and VMX_BASIC_RESERVED_BITS to form a valid bitmask
> of IA32_VMX_BASIC MSR. As a result, to add a new VMX basic feature bit,
> just change the 2 new macros in the header file.
Not if a new feature bit lands in the middle of one of the reserved ranges, then
the developer will have to update at least three macros, and add a new one. More
below.
> Also replace hardcoded VMX basic numbers with the new VMX basic macros.
>
> Tested-by: Shan Kang <[email protected]>
> Signed-off-by: Xin Li <[email protected]>
> ---
> arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
> arch/x86/kvm/vmx/nested.c | 10 +++------
> arch/x86/kvm/vmx/vmx.c | 2 +-
> tools/arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
Please drop the tools/ update, copying kernel headers into tools is a perf tools
thing that I want no part of.
https://lore.kernel.org/all/Y8bZ%2FJ98V5i3wG%[email protected]
> 4 files changed, 52 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index 1d111350197f..4607448ff805 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -1084,13 +1084,30 @@
> #define MSR_IA32_VMX_PROCBASED_CTLS3 0x00000492
>
> /* VMX_BASIC bits and bitmasks */
> -#define VMX_BASIC_VMCS_SIZE_SHIFT 32
> -#define VMX_BASIC_TRUE_CTLS (1ULL << 55)
> -#define VMX_BASIC_64 0x0001000000000000LLU
> -#define VMX_BASIC_MEM_TYPE_SHIFT 50
> -#define VMX_BASIC_MEM_TYPE_MASK 0x003c000000000000LLU
> -#define VMX_BASIC_MEM_TYPE_WB 6LLU
> -#define VMX_BASIC_INOUT 0x0040000000000000LLU
> +#define VMX_BASIC_VMCS_SIZE_SHIFT 32
> +#define VMX_BASIC_ALWAYS_0 BIT_ULL(31)
> +#define VMX_BASIC_RESERVED_RANGE_1 GENMASK_ULL(47, 45)
> +#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT 48
> +#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT)
> +#define VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT 49
> +#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT)
> +#define VMX_BASIC_MEM_TYPE_SHIFT 50
> +#define VMX_BASIC_MEM_TYPE_WB 6LLU
> +#define VMX_BASIC_INOUT_SHIFT 54
> +#define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT)
> +#define VMX_BASIC_TRUE_CTLS_SHIFT 55
> +#define VMX_BASIC_TRUE_CTLS BIT_ULL(VMX_BASIC_TRUE_CTLS_SHIFT)
> +#define VMX_BASIC_RESERVED_RANGE_2 GENMASK_ULL(63, 56)
> +
> +#define VMX_BASIC_FEATURES \
Maybe VMX_BASIC_FEATURES_MASK to make it more obvious it's a mask of multiple
bits?
> + (VMX_BASIC_DUAL_MONITOR_TREATMENT | \
> + VMX_BASIC_INOUT | \
> + VMX_BASIC_TRUE_CTLS)
> +
> +#define VMX_BASIC_RESERVED_BITS \
> + (VMX_BASIC_ALWAYS_0 | \
> + VMX_BASIC_RESERVED_RANGE_1 | \
> + VMX_BASIC_RESERVED_RANGE_2)
I don't see any value in defining VMX_BASIC_RESERVED_RANGE_1 and
VMX_BASIC_RESERVED_RANGE_2 separately. Or VMX_BASIC_ALWAYS_0 for the matter.
And I don't think these macros need to go in msr-index.h, e.g. just define them
above vmx_restore_vmx_basic() as that's likely going to be the only user, ever.
And what's really missing is a static_assert() or BUILD_BUG_ON() to ensure that
VMX_BASIC_FEATURES doesn't overlap with VMX_BASIC_RESERVED_BITS.
> /* Resctrl MSRs: */
> /* - Intel: */
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index c5ec0ef51ff7..5280ba944c87 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -1203,21 +1203,17 @@ static bool is_bitwise_subset(u64 superset, u64 subset, u64 mask)
>
> static int vmx_restore_vmx_basic(struct vcpu_vmx *vmx, u64 data)
> {
> - const u64 feature_and_reserved =
> - /* feature (except bit 48; see below) */
> - BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |
> - /* reserved */
> - BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56);
> u64 vmx_basic = vmcs_config.nested.basic;
>
> - if (!is_bitwise_subset(vmx_basic, data, feature_and_reserved))
> + if (!is_bitwise_subset(vmx_basic, data,
> + VMX_BASIC_FEATURES | VMX_BASIC_RESERVED_BITS))
> return -EINVAL;
>
> /*
> * KVM does not emulate a version of VMX that constrains physical
> * addresses of VMX structures (e.g. VMCS) to 32-bits.
> */
> - if (data & BIT_ULL(48))
> + if (data & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
> return -EINVAL;
>
> if (vmx_basic_vmcs_revision_id(vmx_basic) !=
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 72e3943f3693..f597243d6a72 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2701,7 +2701,7 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>
> #ifdef CONFIG_X86_64
> /* IA-32 SDM Vol 3B: 64-bit CPUs always have VMX_BASIC_MSR[48]==0. */
> - if (vmx_msr_high & (1u<<16))
> + if (vmx_msr_high & (1u << (VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT - 32)))
In all honestly, I find the existing code easier to read. I'm definitely not
saying the existing code is good, but IMO this is at best a wash.
I would much rather we do something like this and move away from the hi/lo crud
entirely:
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 86ce9efe6c66..f103980c3d02 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2693,28 +2693,28 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
_vmexit_control &= ~x_ctrl;
}
- rdmsr(MSR_IA32_VMX_BASIC, vmx_msr_low, vmx_msr_high);
+ rdmsrl(MSR_IA32_VMX_BASIC, vmx_msr);
/* IA-32 SDM Vol 3B: VMCS size is never greater than 4kB. */
- if ((vmx_msr_high & 0x1fff) > PAGE_SIZE)
+ if ((VMX_BASIC_VMCS_SIZE(vmx_msr) > PAGE_SIZE)
return -EIO;
#ifdef CONFIG_X86_64
/* IA-32 SDM Vol 3B: 64-bit CPUs always have VMX_BASIC_MSR[48]==0. */
- if (vmx_msr_high & (1u<<16))
+ if (vmx_msr & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
return -EIO;
#endif
/* Require Write-Back (WB) memory type for VMCS accesses. */
- if (((vmx_msr_high >> 18) & 15) != 6)
+ if (VMX_BASIC_VMCS_MEMTYPE(vmx_msr) != VMX_BASIC_MEM_TYPE_WB)
return -EIO;
rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
- vmcs_conf->size = vmx_msr_high & 0x1fff;
- vmcs_conf->basic_cap = vmx_msr_high & ~0x1fff;
+ vmcs_conf->size = VMX_BASIC_VMCS_SIZE(vmx_msr);
+ vmcs_conf->basic_cap = ????(vmx_msr);
- vmcs_conf->revision_id = vmx_msr_low;
+ vmcs_conf->revision_id = (u32)vmx_msr;
vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;
On 10/18/2023 2:08 PM, Sean Christopherson wrote:
>> Add IA32_VMX_BASIC MSR bitfield shift macros and use them to define VMX
>> basic information bitfields.
>
> Why? Unless something actually uses the shift independently, just define the
> BIT_ULL(...) straightaway.
Well, reading "BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |" is hard.
But Lemme remove those shifts not being used now.
>> Add VMX_BASIC_FEATURES and VMX_BASIC_RESERVED_BITS to form a valid bitmask
>> of IA32_VMX_BASIC MSR. As a result, to add a new VMX basic feature bit,
>> just change the 2 new macros in the header file.
>
> Not if a new feature bit lands in the middle of one of the reserved ranges, then
> the developer will have to update at least three macros, and add a new one. More
> below.
yes, it is the case for VMX nested exception feature bit.
>
>> Also replace hardcoded VMX basic numbers with the new VMX basic macros.
>>
>> Tested-by: Shan Kang <[email protected]>
>> Signed-off-by: Xin Li <[email protected]>
>> ---
>> arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
>> arch/x86/kvm/vmx/nested.c | 10 +++------
>> arch/x86/kvm/vmx/vmx.c | 2 +-
>> tools/arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
>
> Please drop the tools/ update, copying kernel headers into tools is a perf tools
> thing that I want no part of.
>
> https://lore.kernel.org/all/Y8bZ%2FJ98V5i3wG%[email protected]
why can't we simply remove tools/arch/x86/include/asm/msr-index.h?
>
>> 4 files changed, 52 insertions(+), 22 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
>> index 1d111350197f..4607448ff805 100644
>> --- a/arch/x86/include/asm/msr-index.h
>> +++ b/arch/x86/include/asm/msr-index.h
>> @@ -1084,13 +1084,30 @@
>> #define MSR_IA32_VMX_PROCBASED_CTLS3 0x00000492
>>
>> /* VMX_BASIC bits and bitmasks */
>> -#define VMX_BASIC_VMCS_SIZE_SHIFT 32
>> -#define VMX_BASIC_TRUE_CTLS (1ULL << 55)
>> -#define VMX_BASIC_64 0x0001000000000000LLU
>> -#define VMX_BASIC_MEM_TYPE_SHIFT 50
>> -#define VMX_BASIC_MEM_TYPE_MASK 0x003c000000000000LLU
>> -#define VMX_BASIC_MEM_TYPE_WB 6LLU
>> -#define VMX_BASIC_INOUT 0x0040000000000000LLU
>> +#define VMX_BASIC_VMCS_SIZE_SHIFT 32
>> +#define VMX_BASIC_ALWAYS_0 BIT_ULL(31)
>> +#define VMX_BASIC_RESERVED_RANGE_1 GENMASK_ULL(47, 45)
>> +#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT 48
>> +#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT)
>> +#define VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT 49
>> +#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT)
>> +#define VMX_BASIC_MEM_TYPE_SHIFT 50
>> +#define VMX_BASIC_MEM_TYPE_WB 6LLU
>> +#define VMX_BASIC_INOUT_SHIFT 54
>> +#define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT)
>> +#define VMX_BASIC_TRUE_CTLS_SHIFT 55
>> +#define VMX_BASIC_TRUE_CTLS BIT_ULL(VMX_BASIC_TRUE_CTLS_SHIFT)
>> +#define VMX_BASIC_RESERVED_RANGE_2 GENMASK_ULL(63, 56)
>> +
>> +#define VMX_BASIC_FEATURES \
>
> Maybe VMX_BASIC_FEATURES_MASK to make it more obvious it's a mask of multiple
> bits?
This is better!
>
>> + (VMX_BASIC_DUAL_MONITOR_TREATMENT | \
>> + VMX_BASIC_INOUT | \
>> + VMX_BASIC_TRUE_CTLS)
>> +
>> +#define VMX_BASIC_RESERVED_BITS \
>> + (VMX_BASIC_ALWAYS_0 | \
>> + VMX_BASIC_RESERVED_RANGE_1 | \
>> + VMX_BASIC_RESERVED_RANGE_2)
>
> I don't see any value in defining VMX_BASIC_RESERVED_RANGE_1 and
> VMX_BASIC_RESERVED_RANGE_2 separately. Or VMX_BASIC_ALWAYS_0 for the matter.
> And I don't think these macros need to go in msr-index.h, e.g. just define them
> above vmx_restore_vmx_basic() as that's likely going to be the only user, ever.
hmm, I'm overusing macros, better do:
#define VMX_BASIC_RESERVED_BITS \
(BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56))
Probably should also move VMX MSR field defs from msr-index.h to
a vmx header file.
>
> And what's really missing is a static_assert() or BUILD_BUG_ON() to ensure that
> VMX_BASIC_FEATURES doesn't overlap with VMX_BASIC_RESERVED_BITS.
good idea, human beings are not good at such jobs by staring at it.
>
>> /* Resctrl MSRs: */
>> /* - Intel: */
>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>> index c5ec0ef51ff7..5280ba944c87 100644
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -1203,21 +1203,17 @@ static bool is_bitwise_subset(u64 superset, u64 subset, u64 mask)
>>
>> static int vmx_restore_vmx_basic(struct vcpu_vmx *vmx, u64 data)
>> {
>> - const u64 feature_and_reserved =
>> - /* feature (except bit 48; see below) */
>> - BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |
>> - /* reserved */
>> - BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56);
>> u64 vmx_basic = vmcs_config.nested.basic;
>>
>> - if (!is_bitwise_subset(vmx_basic, data, feature_and_reserved))
>> + if (!is_bitwise_subset(vmx_basic, data,
>> + VMX_BASIC_FEATURES | VMX_BASIC_RESERVED_BITS))
>> return -EINVAL;
>>
>> /*
>> * KVM does not emulate a version of VMX that constrains physical
>> * addresses of VMX structures (e.g. VMCS) to 32-bits.
>> */
>> - if (data & BIT_ULL(48))
>> + if (data & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
>> return -EINVAL;
>>
>> if (vmx_basic_vmcs_revision_id(vmx_basic) !=
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 72e3943f3693..f597243d6a72 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -2701,7 +2701,7 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>>
>> #ifdef CONFIG_X86_64
>> /* IA-32 SDM Vol 3B: 64-bit CPUs always have VMX_BASIC_MSR[48]==0. */
>> - if (vmx_msr_high & (1u<<16))
>> + if (vmx_msr_high & (1u << (VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT - 32)))
>
> In all honestly, I find the existing code easier to read. I'm definitely not
> saying the existing code is good, but IMO this is at best a wash.
>
> I would much rather we do something like this and move away from the hi/lo crud
> entirely:
I ever saw a TDX patch does most of this cleanup.
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 86ce9efe6c66..f103980c3d02 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2693,28 +2693,28 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> _vmexit_control &= ~x_ctrl;
> }
>
> - rdmsr(MSR_IA32_VMX_BASIC, vmx_msr_low, vmx_msr_high);
> + rdmsrl(MSR_IA32_VMX_BASIC, vmx_msr);
>
> /* IA-32 SDM Vol 3B: VMCS size is never greater than 4kB. */
> - if ((vmx_msr_high & 0x1fff) > PAGE_SIZE)
> + if ((VMX_BASIC_VMCS_SIZE(vmx_msr) > PAGE_SIZE)
> return -EIO;
>
> #ifdef CONFIG_X86_64
> /* IA-32 SDM Vol 3B: 64-bit CPUs always have VMX_BASIC_MSR[48]==0. */
> - if (vmx_msr_high & (1u<<16))
> + if (vmx_msr & VMX_BASIC_32BIT_PHYS_ADDR_ONLY)
> return -EIO;
> #endif
>
> /* Require Write-Back (WB) memory type for VMCS accesses. */
> - if (((vmx_msr_high >> 18) & 15) != 6)
> + if (VMX_BASIC_VMCS_MEMTYPE(vmx_msr) != VMX_BASIC_MEM_TYPE_WB)
> return -EIO;
>
> rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
>
> - vmcs_conf->size = vmx_msr_high & 0x1fff;
> - vmcs_conf->basic_cap = vmx_msr_high & ~0x1fff;
> + vmcs_conf->size = VMX_BASIC_VMCS_SIZE(vmx_msr);
> + vmcs_conf->basic_cap = ????(vmx_msr);
>
> - vmcs_conf->revision_id = vmx_msr_low;
> + vmcs_conf->revision_id = (u32)vmx_msr;
>
> vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
> vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;
>
--
Thanks!
Xin
On Thu, Oct 19, 2023, Xin Li wrote:
> On 10/18/2023 2:08 PM, Sean Christopherson wrote:
>
> > > Add IA32_VMX_BASIC MSR bitfield shift macros and use them to define VMX
> > > basic information bitfields.
> >
> > Why? Unless something actually uses the shift independently, just define the
> > BIT_ULL(...) straightaway.
>
> Well, reading "BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |" is hard.
I wasn't suggesting that, I was suggesting:
#define VMX_BASIC_INOUT BIT_ULL(54)
instead of
#define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT)
Defining a shift adds a pointless layer of indirection (if the shift isn't used
directly). It's especially problematic when there are a series of definitions.
E.g. if I want to know which bit a flag corresponds to, this:
#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(48)
#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(49)
#define VMX_BASIC_MEM_TYPE(x) (((x) & GENMASK_ULL(53, 50)) >> 50)
#define VMX_BASIC_INOUT BIT_ULL(54)
#define VMX_BASIC_TRUE_CTLS BIT_ULL(55)
is much easier for me to process than this
#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT 48
#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(VMX_BASIC_32BIT_PHYS_ADDR_ONLY_SHIFT)
#define VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT 49
#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(VMX_BASIC_DUAL_MONITOR_TREATMENT_SHIFT)
#define VMX_BASIC_MEM_TYPE_SHIFT 50
#define VMX_BASIC_INOUT_SHIFT 54
#define VMX_BASIC_INOUT BIT_ULL(VMX_BASIC_INOUT_SHIFT)
#define VMX_BASIC_TRUE_CTLS_SHIFT 55
#define VMX_BASIC_TRUE_CTLS BIT_ULL(VMX_BASIC_TRUE_CTLS_SHIFT)
and the former also tends to work better for IDEs that support peeking at macro
definitions.
> > > ---
> > > arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
> > > arch/x86/kvm/vmx/nested.c | 10 +++------
> > > arch/x86/kvm/vmx/vmx.c | 2 +-
> > > tools/arch/x86/include/asm/msr-index.h | 31 ++++++++++++++++++++------
> >
> > Please drop the tools/ update, copying kernel headers into tools is a perf tools
> > thing that I want no part of.
> >
> > https://lore.kernel.org/all/Y8bZ%2FJ98V5i3wG%[email protected]
>
> why can't we simply remove tools/arch/x86/include/asm/msr-index.h?
That's a question for the tools/perf folks, though I believe the answer is partly
that the perf tooling relies on *exactly* matching kernel-internal structures, and
so tools/perf doesn't want to rely on installed headers.
> > > +#define VMX_BASIC_RESERVED_BITS \
> > > + (VMX_BASIC_ALWAYS_0 | \
> > > + VMX_BASIC_RESERVED_RANGE_1 | \
> > > + VMX_BASIC_RESERVED_RANGE_2)
> >
> > I don't see any value in defining VMX_BASIC_RESERVED_RANGE_1 and
> > VMX_BASIC_RESERVED_RANGE_2 separately. Or VMX_BASIC_ALWAYS_0 for the matter.
> > And I don't think these macros need to go in msr-index.h, e.g. just define them
> > above vmx_restore_vmx_basic() as that's likely going to be the only user, ever.
>
> hmm, I'm overusing macros, better do:
> #define VMX_BASIC_RESERVED_BITS \
> (BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56))
Please define from high=>low, x86 is little-endian. I.e.
(GENMASK_ULL(63, 56) | GENMASK_ULL(47, 45) | BIT_ULL(31))
> Probably should also move VMX MSR field defs from msr-index.h to
> a vmx header file.
Why bother putting them in a header? As above, it's extremely unlikely anything
besides vmx_restore_vmx_basic() will ever care about exactly which bits are
reserved.