From: "Yang, Weijiang" <weijiang.yang@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: <pbonzini@redhat.com>, <dave.hansen@intel.com>, <x86@kernel.org>,
<kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<peterz@infradead.org>, <chao.gao@intel.com>,
<rick.p.edgecombe@intel.com>, <mlevitsk@redhat.com>,
<john.allen@amd.com>
Subject: Re: [PATCH v10 17/27] KVM: x86: Report KVM supported CET MSRs as to-be-saved
Date: Wed, 8 May 2024 15:00:12 +0800 [thread overview]
Message-ID: <5a8c31bd-0fe3-48f2-8ec3-b143fe289827@intel.com> (raw)
In-Reply-To: <Zjpkl0U23qEOO3DY@google.com>
On 5/8/2024 1:27 AM, Sean Christopherson wrote:
> On Mon, May 06, 2024, Weijiang Yang wrote:
>> On 5/2/2024 6:40 AM, Sean Christopherson wrote:
>>> On Sun, Feb 18, 2024, Yang Weijiang wrote:
[...]
>> For the latter, IIUC KVM still needs to expose the index within the synthetic
>> namespace so that userspace can read/write the intended MSRs, of course not
>> expose the synthetic MSR index via existing uAPI, But you said the "index"
>> exposed to userspace can simply be '0' in this case, then how to distinguish
>> the synthetic MSRs in userspace and KVM? And how userspace can be aware of
>> the synthetic MSR index allocation in KVM?
> The idea is to have a synthetic index that is exposed to userspace, and a separate
> KVM-internal index for emulating accesses. The value that is exposed to userspace
> can start at 0 and be a simple incrementing value as we add synthetic MSRs, as the
> .type == SYNTHETIC makes it impossible for the value to collide with a "real" MSR.
>
> Translating to a KVM-internal index is a hack to avoid having to plumb a 64-bit
> index into all the MSR code. We could do that, i.e. pass the full kvm_x86_reg_id
> into the MSR helpers, but I'm not convinced it'd be worth the churn. That said,
> I'm not opposed to the idea either, if others prefer that approach.
>
> E.g.
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 738c449e4f9e..21152796238a 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -420,6 +420,8 @@ struct kvm_x86_reg_id {
> __u16 rsvd16;
> };
>
> +#define MSR_KVM_GUEST_SSP 0
> +
> #define KVM_SYNC_X86_REGS (1UL << 0)
> #define KVM_SYNC_X86_SREGS (1UL << 1)
> #define KVM_SYNC_X86_EVENTS (1UL << 2)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f45cdd9d8c1f..1a9e1e0c9f49 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5990,6 +5990,19 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
> }
> }
>
> +static int kvm_translate_synthetic_msr(u32 *index)
> +{
> + switch (*index) {
> + case MSR_KVM_GUEST_SSP:
> + *index = MSR_KVM_INTERNAL_GUEST_SSP;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> long kvm_arch_vcpu_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg)
> {
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index cc585051d24b..3b5a038f5260 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -49,6 +49,15 @@ void kvm_spurious_fault(void);
> #define KVM_FIRST_EMULATED_VMX_MSR MSR_IA32_VMX_BASIC
> #define KVM_LAST_EMULATED_VMX_MSR MSR_IA32_VMX_VMFUNC
>
> +/*
> + * KVM's internal, non-ABI indices for synthetic MSRs. The values themselves
> + * are arbitrary and have no meaning, the only requirement is that they don't
> + * conflict with "real" MSRs that KVM supports. Use values at the uppper end
> + * of KVM's reserved paravirtual MSR range to minimize churn, i.e. these values
> + * will be usable until KVM exhausts its supply of paravirtual MSR indices.
> + */
> +#define MSR_KVM_INTERNAL_GUEST_SSP 0x4b564dff
> +
> #define KVM_DEFAULT_PLE_GAP 128
> #define KVM_VMX_DEFAULT_PLE_WINDOW 4096
> #define KVM_DEFAULT_PLE_WINDOW_GROW 2
OK, I'll post an RFC patch for this change, thanks a lot!
next prev parent reply other threads:[~2024-05-08 7:00 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-19 7:47 [PATCH v10 00/27] Enable CET Virtualization Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 01/27] x86/fpu/xstate: Always preserve non-user xfeatures/flags in __state_perm Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 02/27] x86/fpu/xstate: Refine CET user xstate bit enabling Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 03/27] x86/fpu/xstate: Add CET supervisor mode state support Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 04/27] x86/fpu/xstate: Introduce XFEATURE_MASK_KERNEL_DYNAMIC xfeature set Yang Weijiang
2024-05-01 18:45 ` Sean Christopherson
2024-05-02 17:46 ` Dave Hansen
2024-05-07 22:57 ` Sean Christopherson
2024-05-07 23:17 ` Dave Hansen
2024-05-08 1:19 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 05/27] x86/fpu/xstate: Introduce fpu_guest_cfg for guest FPU configuration Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 06/27] x86/fpu/xstate: Create guest fpstate with guest specific config Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 07/27] x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal fpstate Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 08/27] KVM: x86: Rework cpuid_get_supported_xcr0() to operate on vCPU data Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 09/27] KVM: x86: Rename kvm_{g,s}et_msr()* to menifest emulation operations Yang Weijiang
2024-05-01 18:54 ` Sean Christopherson
2024-05-06 5:58 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 10/27] KVM: x86: Refine xsave-managed guest register/MSR reset handling Yang Weijiang
2024-02-20 3:04 ` Chao Gao
2024-02-20 13:23 ` Yang, Weijiang
2024-05-01 20:40 ` Sean Christopherson
2024-05-06 7:26 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 11/27] KVM: x86: Add kvm_msr_{read,write}() helpers Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 12/27] KVM: x86: Report XSS as to-be-saved if there are supported features Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 13/27] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS Yang Weijiang
2024-02-20 8:51 ` Chao Gao
2024-05-01 20:43 ` Sean Christopherson
2024-05-06 7:30 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 14/27] KVM: x86: Initialize kvm_caps.supported_xss Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 15/27] KVM: x86: Load guest FPU state when access XSAVE-managed MSRs Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 16/27] KVM: x86: Add fault checks for guest CR4.CET setting Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 17/27] KVM: x86: Report KVM supported CET MSRs as to-be-saved Yang Weijiang
2024-05-01 22:40 ` Sean Christopherson
2024-05-06 8:31 ` Yang, Weijiang
2024-05-07 17:27 ` Sean Christopherson
2024-05-08 7:00 ` Yang, Weijiang [this message]
2024-02-19 7:47 ` [PATCH v10 18/27] KVM: VMX: Introduce CET VMCS fields and control bits Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 19/27] KVM: x86: Use KVM-governed feature framework to track "SHSTK/IBT enabled" Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 20/27] KVM: VMX: Emulate read and write to CET MSRs Yang Weijiang
2024-03-12 22:55 ` Sean Christopherson
2024-03-13 9:43 ` Yang, Weijiang
2024-03-13 16:00 ` Sean Christopherson
2024-02-19 7:47 ` [PATCH v10 21/27] KVM: x86: Save and reload SSP to/from SMRAM Yang Weijiang
2024-05-01 22:50 ` Sean Christopherson
2024-05-06 8:41 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 22/27] KVM: VMX: Set up interception for CET MSRs Yang Weijiang
2024-05-01 23:07 ` Sean Christopherson
2024-05-06 8:48 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 23/27] KVM: VMX: Set host constant supervisor states to VMCS fields Yang Weijiang
2024-02-19 7:47 ` [PATCH v10 24/27] KVM: x86: Enable CET virtualization for VMX and advertise to userspace Yang Weijiang
2024-05-01 23:15 ` Sean Christopherson
2024-05-01 23:24 ` Edgecombe, Rick P
2024-05-06 9:19 ` Yang, Weijiang
2024-05-06 16:54 ` Sean Christopherson
2024-05-07 2:37 ` Yang, Weijiang
2024-05-06 17:05 ` Edgecombe, Rick P
2024-05-06 23:33 ` Sean Christopherson
2024-05-06 23:53 ` Edgecombe, Rick P
2024-05-07 14:21 ` Sean Christopherson
2024-05-07 14:45 ` Edgecombe, Rick P
2024-05-07 15:08 ` Sean Christopherson
2024-05-07 15:33 ` Edgecombe, Rick P
2024-05-16 7:13 ` Yang, Weijiang
2024-05-16 14:39 ` Sean Christopherson
2024-05-16 15:36 ` Dave Hansen
2024-05-16 16:58 ` Sean Christopherson
2024-05-17 8:27 ` Yang, Weijiang
2024-05-17 8:57 ` Thomas Gleixner
2024-05-17 14:26 ` Sean Christopherson
2024-05-20 9:43 ` Yang, Weijiang
2024-05-20 17:09 ` Sean Christopherson
2024-05-20 17:15 ` Dave Hansen
2024-05-01 23:34 ` Sean Christopherson
2024-05-06 9:41 ` Yang, Weijiang
2024-05-16 7:20 ` Yang, Weijiang
2024-05-16 14:43 ` Sean Christopherson
2024-05-17 8:04 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 25/27] KVM: nVMX: Introduce new VMX_BASIC bit for event error_code delivery to L1 Yang Weijiang
2024-05-01 23:19 ` Sean Christopherson
2024-05-06 9:19 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 26/27] KVM: nVMX: Enable CET support for nested guest Yang Weijiang
2024-05-01 23:23 ` Sean Christopherson
2024-05-06 9:25 ` Yang, Weijiang
2024-02-19 7:47 ` [PATCH v10 27/27] KVM: x86: Don't emulate instructions guarded by CET Yang Weijiang
2024-05-01 23:24 ` Sean Christopherson
2024-05-06 9:26 ` Yang, Weijiang
2024-03-06 14:44 ` [PATCH v10 00/27] Enable CET Virtualization Yang, Weijiang
2024-05-01 23:27 ` Sean Christopherson
2024-05-06 9:31 ` Yang, Weijiang
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