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Date: Fri, 27 Oct 2023 09:29:32 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"xin@...or.com" <xin@...or.com>
CC: "Yang, Weijiang" <weijiang.yang@...el.com>,
"Christopherson,, Sean" <seanjc@...gle.com>,
"x86@...nel.org" <x86@...nel.org>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"hpa@...or.com" <hpa@...or.com>,
"mingo@...hat.com" <mingo@...hat.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"bp@...en8.de" <bp@...en8.de>,
"pbonzini@...hat.com" <pbonzini@...hat.com>
Subject: Re: [PATCH v2 1/2] KVM: VMX: Cleanup VMX basic information defines
and usages
>
> +/* VMX_BASIC bits and bitmasks */
> +#define VMX_BASIC_32BIT_PHYS_ADDR_ONLY BIT_ULL(48)
> +#define VMX_BASIC_MEM_TYPE_WB 6LLU
Strictly speaking, VMX_BASIC_MEM_TYPE_MB isn't any bit definition or bitmasks of
VMX_BASIC MSR. So perhaps better to put it somewhere under separately.
> +#define VMX_BASIC_INOUT BIT_ULL(54)
> +
> +/* VMX_MISC bits and bitmasks */
Your next patch is to "Cleanup VMX misc information defines and usages", so I
guess it's better to move any VMX_MISC related change to that patch.
> #define VMX_MISC_PREEMPTION_TIMER_RATE_MASK 0x0000001f
> #define VMX_MISC_SAVE_EFER_LMA 0x00000020
> #define VMX_MISC_ACTIVITY_HLT 0x00000040
> @@ -143,6 +149,16 @@ static inline u32 vmx_basic_vmcs_size(u64 vmx_basic)
> return (vmx_basic & GENMASK_ULL(44, 32)) >> 32;
> }
>
> +static inline u32 vmx_basic_vmcs_basic_cap(u64 vmx_basic)
> +{
> + return (vmx_basic & GENMASK_ULL(63, 45)) >> 32;
> +}
> +
> +static inline u32 vmx_basic_vmcs_mem_type(u64 vmx_basic)
> +{
> + return (vmx_basic & GENMASK_ULL(53, 50)) >> 50;
> +}
> +
> static inline int vmx_misc_preemption_timer_rate(u64 vmx_misc)
> {
> return vmx_misc & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 4ba46e1b29d2..274d480d9071 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -1201,23 +1201,34 @@ static bool is_bitwise_subset(u64 superset, u64 subset, u64 mask)
> return (superset | subset) == superset;
> }
>
> +#define VMX_BASIC_VMCS_SIZE_SHIFT 32
> +#define VMX_BASIC_DUAL_MONITOR_TREATMENT BIT_ULL(49)
> +#define VMX_BASIC_MEM_TYPE_SHIFT 50
> +#define VMX_BASIC_TRUE_CTLS BIT_ULL(55)
If I am reading correctly, the two "*_SHIFT" above are not used? The above
vmx_basic_vmcs_mem_type() and vmx_basic_vmcs_basic_cap() use hard-coded values
directly.
And How about moving all these bit/mask definitions to <asm/vmx.h> above?
It's better they stay together for better readability.
> +
> +#define VMX_BASIC_FEATURES_MASK \
> + (VMX_BASIC_DUAL_MONITOR_TREATMENT | \
> + VMX_BASIC_INOUT | \
> + VMX_BASIC_TRUE_CTLS)
> +
> +#define VMX_BASIC_RESERVED_BITS \
> + (GENMASK_ULL(63, 56) | GENMASK_ULL(47, 45) | BIT_ULL(31))
> +
Also move these to <asm/vmx.h>?
> 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))
> + static_assert(!(VMX_BASIC_FEATURES_MASK & VMX_BASIC_RESERVED_BITS));
> +
> + if (!is_bitwise_subset(vmx_basic, data,
> + VMX_BASIC_FEATURES_MASK | 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 4c3a70f26b42..b68d54f6e9f8 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2568,14 +2568,13 @@ static u64 adjust_vmx_controls64(u64 ctl_opt, u32 msr)
> static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> struct vmx_capability *vmx_cap)
> {
> - u32 vmx_msr_low, vmx_msr_high;
> u32 _pin_based_exec_control = 0;
> u32 _cpu_based_exec_control = 0;
> u32 _cpu_based_2nd_exec_control = 0;
> u64 _cpu_based_3rd_exec_control = 0;
> u32 _vmexit_control = 0;
> u32 _vmentry_control = 0;
> - u64 misc_msr;
> + u64 vmx_basic;
> int i;
>
> /*
> @@ -2693,28 +2692,26 @@ 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_basic);
>
> /* 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_basic) > 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_basic & 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_mem_type(vmx_basic) != 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_basic);
> + vmcs_conf->basic_cap = vmx_basic_vmcs_basic_cap(vmx_basic);
>
> - vmcs_conf->revision_id = vmx_msr_low;
> + vmcs_conf->revision_id = vmx_basic_vmcs_revision_id(vmx_basic);
I actually tried to do similar thing before, and Sean gave me below advice:
Rather than do all of these weird dances, what about saving the
full/raw
MSR in the config, and then using the helpers to extract info as
needed?
https://lkml.kernel.org/kvm/20230330092149.101047-1-kai.huang@intel.com/T/#m4879a3c7e66ede7bfa568a25aea4f6e3778e6e34
I agreed, but I has been too lazy to do this, sorry :-)
So maybe we should still go with this approach?
>
> vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
> vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;
> @@ -2722,7 +2719,8 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> vmcs_conf->cpu_based_3rd_exec_ctrl = _cpu_based_3rd_exec_control;
> vmcs_conf->vmexit_ctrl = _vmexit_control;
> vmcs_conf->vmentry_ctrl = _vmentry_control;
> - vmcs_conf->misc = misc_msr;
> +
> + rdmsrl(MSR_IA32_VMX_MISC, vmcs_conf->misc);
Better to move VMX_MISC code to next patch I suppose.
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