From: "Yang, Weijiang" <weijiang.yang@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: <pbonzini@redhat.com>, <peterz@infradead.org>,
<john.allen@amd.com>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <rick.p.edgecombe@intel.com>,
<chao.gao@intel.com>, <binbin.wu@linux.intel.com>,
Zhang Yi Z <yi.z.zhang@linux.intel.com>
Subject: Re: [PATCH v5 04/19] KVM:x86: Refresh CPUID on write to guest MSR_IA32_XSS
Date: Tue, 8 Aug 2023 22:20:37 +0800 [thread overview]
Message-ID: <d888f479-370a-00d3-b929-780e0600dee5@intel.com> (raw)
In-Reply-To: <ZM0hG7Pn/fkGruWu@google.com>
On 8/5/2023 12:02 AM, Sean Christopherson wrote:
> On Thu, Aug 03, 2023, Yang Weijiang wrote:
>> Update CPUID(EAX=0DH,ECX=1) when the guest's XSS is modified.
>> CPUID(EAX=0DH,ECX=1).EBX reports required storage size of
>> all enabled xstate features in XCR0 | XSS. Guest can allocate
>> sufficient xsave buffer based on the info.
> Please wrap changelogs closer to ~75 chars. I'm pretty sure this isn't the first
> time I've made this request...
Thanks, will keep the changelog to 70~75 chars.
>> Note, KVM does not yet support any XSS based features, i.e.
>> supported_xss is guaranteed to be zero at this time.
>>
>> Co-developed-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
>> Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
>> ---
>> arch/x86/include/asm/kvm_host.h | 1 +
>> arch/x86/kvm/cpuid.c | 20 ++++++++++++++++++--
>> arch/x86/kvm/x86.c | 8 +++++---
>> 3 files changed, 24 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 28bd38303d70..20bbcd95511f 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -804,6 +804,7 @@ struct kvm_vcpu_arch {
>>
>> u64 xcr0;
>> u64 guest_supported_xcr0;
>> + u64 guest_supported_xss;
>>
>> struct kvm_pio_request pio;
>> void *pio_data;
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index 7f4d13383cf2..0338316b827c 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -249,6 +249,17 @@ static u64 cpuid_get_supported_xcr0(struct kvm_cpuid_entry2 *entries, int nent)
>> return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0;
>> }
>>
>> +static u64 cpuid_get_supported_xss(struct kvm_cpuid_entry2 *entries, int nent)
>> +{
>> + struct kvm_cpuid_entry2 *best;
>> +
>> + best = cpuid_entry2_find(entries, nent, 0xd, 1);
>> + if (!best)
>> + return 0;
>> +
>> + return (best->ecx | ((u64)best->edx << 32)) & kvm_caps.supported_xss;
>> +}
>> +
>> static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *entries,
>> int nent)
>> {
>> @@ -276,8 +287,11 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
>>
>> best = cpuid_entry2_find(entries, nent, 0xD, 1);
>> if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
>> - cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
>> - best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
>> + cpuid_entry_has(best, X86_FEATURE_XSAVEC))) {
>> + u64 xstate = vcpu->arch.xcr0 | vcpu->arch.ia32_xss;
> Nit, the variable should be xfeatures, not xstate. Though I vote to avoid the
> variable entirely,
>
> best = cpuid_entry2_find(entries, nent, 0xD, 1);
> if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
> best->ebx = xstate_required_size(vcpu->arch.xcr0 |
> vcpu->arch.ia32_xss, true);
>
> though it's only a slight preference, i.e. feel free to keep your approach if
> you or others feel strongly about the style.
Yes, the variable is not necessary, will remove it.
>> + }
>>
>> best = __kvm_find_kvm_cpuid_features(vcpu, entries, nent);
>> if (kvm_hlt_in_guest(vcpu->kvm) && best &&
>> @@ -325,6 +339,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
>>
>> vcpu->arch.guest_supported_xcr0 =
>> cpuid_get_supported_xcr0(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);
>> + vcpu->arch.guest_supported_xss =
>> + cpuid_get_supported_xss(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);
> Blech. I tried to clean up this ugly, but Paolo disagreed[*]. Can you fold in
> the below (compile tested only) patch at the very beginning of this series? It
> implements my suggested alternative. And then this would become:
>
> static u64 vcpu_get_supported_xss(struct kvm_vcpu *vcpu)
> {
> struct kvm_cpuid_entry2 *best;
>
> best = kvm_find_cpuid_entry_index(vcpu, 0xd, 1);
> if (!best)
> return 0;
>
> return (best->ecx | ((u64)best->edx << 32)) & kvm_caps.supported_xss;
> }
>
> [*] https://lore.kernel.org/all/ZGfius5UkckpUyXl@google.com
Sure, will take it into my series, thanks!
>> /*
>> * FP+SSE can always be saved/restored via KVM_{G,S}ET_XSAVE, even if
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 0b9033551d8c..5d6d6fa33e5b 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -3780,10 +3780,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>> * IA32_XSS[bit 8]. Guests have to use RDMSR/WRMSR rather than
>> * XSAVES/XRSTORS to save/restore PT MSRs.
>> */
>> - if (data & ~kvm_caps.supported_xss)
>> + if (data & ~vcpu->arch.guest_supported_xss)
>> return 1;
>> - vcpu->arch.ia32_xss = data;
>> - kvm_update_cpuid_runtime(vcpu);
>> + if (vcpu->arch.ia32_xss != data) {
>> + vcpu->arch.ia32_xss = data;
>> + kvm_update_cpuid_runtime(vcpu);
>> + }
> Nit, I prefer this style:
>
> if (vcpu->arch.ia32_xss == data)
> break;
>
> vcpu->arch.ia32_xss = data;
> kvm_update_cpuid_runtime(vcpu);
>
> so that the common path isn't buried in an if-statement.
Yeah, I feel I'm a bit awkward to make code look nicer :-)
>> break;
>> case MSR_SMI_COUNT:
>> if (!msr_info->host_initiated)
>> --
>
> From: Sean Christopherson <seanjc@google.com>
> Date: Fri, 4 Aug 2023 08:48:03 -0700
> Subject: [PATCH] KVM: x86: Rework cpuid_get_supported_xcr0() to operate on
> vCPU data
>
> Rework and rename cpuid_get_supported_xcr0() to explicitly operate on vCPU
> state, i.e. on a vCPU's CPUID state. Prior to commit 275a87244ec8 ("KVM:
> x86: Don't adjust guest's CPUID.0x12.1 (allowed SGX enclave XFRM)"), KVM
> incorrectly fudged guest CPUID at runtime, which in turn necessitated
> massaging the incoming CPUID state for KVM_SET_CPUID{2} so as not to run
> afoul of kvm_cpuid_check_equal().
>
> Opportunistically move the helper below kvm_update_cpuid_runtime() to make
> it harder to repeat the mistake of querying supported XCR0 for runtime
> updates.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/cpuid.c | 33 ++++++++++++++++-----------------
> 1 file changed, 16 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 7f4d13383cf2..5e42846c948a 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -234,21 +234,6 @@ void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
> vcpu->arch.pv_cpuid.features = best->eax;
> }
>
> -/*
> - * Calculate guest's supported XCR0 taking into account guest CPUID data and
> - * KVM's supported XCR0 (comprised of host's XCR0 and KVM_SUPPORTED_XCR0).
> - */
> -static u64 cpuid_get_supported_xcr0(struct kvm_cpuid_entry2 *entries, int nent)
> -{
> - struct kvm_cpuid_entry2 *best;
> -
> - best = cpuid_entry2_find(entries, nent, 0xd, 0);
> - if (!best)
> - return 0;
> -
> - return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0;
> -}
> -
> static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *entries,
> int nent)
> {
> @@ -299,6 +284,21 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
> }
> EXPORT_SYMBOL_GPL(kvm_update_cpuid_runtime);
>
> +/*
> + * Calculate guest's supported XCR0 taking into account guest CPUID data and
> + * KVM's supported XCR0 (comprised of host's XCR0 and KVM_SUPPORTED_XCR0).
> + */
> +static u64 vcpu_get_supported_xcr0(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_cpuid_entry2 *best;
> +
> + best = kvm_find_cpuid_entry_index(vcpu, 0xd, 0);
> + if (!best)
> + return 0;
> +
> + return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0;
> +}
> +
> static bool kvm_cpuid_has_hyperv(struct kvm_cpuid_entry2 *entries, int nent)
> {
> struct kvm_cpuid_entry2 *entry;
> @@ -323,8 +323,7 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
> kvm_apic_set_version(vcpu);
> }
>
> - vcpu->arch.guest_supported_xcr0 =
> - cpuid_get_supported_xcr0(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);
> + vcpu->arch.guest_supported_xcr0 = vcpu_get_supported_xcr0(vcpu);
>
> /*
> * FP+SSE can always be saved/restored via KVM_{G,S}ET_XSAVE, even if
>
> base-commit: f0147fcfab840fe9a3f03e9645d25c1326373fe6
next prev parent reply other threads:[~2023-08-08 17:28 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-03 4:27 [PATCH v5 00/19] Enable CET Virtualization Yang Weijiang
2023-08-03 4:27 ` [PATCH v5 01/19] x86/cpufeatures: Add CPU feature flags for shadow stacks Yang Weijiang
2023-08-03 4:27 ` [PATCH v5 02/19] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Yang Weijiang
2023-08-03 4:27 ` [PATCH v5 03/19] KVM:x86: Report XSS as to-be-saved if there are supported features Yang Weijiang
2023-08-03 4:27 ` [PATCH v5 04/19] KVM:x86: Refresh CPUID on write to guest MSR_IA32_XSS Yang Weijiang
2023-08-04 16:02 ` Sean Christopherson
2023-08-04 21:43 ` Paolo Bonzini
2023-08-09 3:11 ` Yang, Weijiang
2023-08-08 14:20 ` Yang, Weijiang [this message]
2023-08-04 18:27 ` Sean Christopherson
2023-08-07 6:55 ` Paolo Bonzini
2023-08-09 8:56 ` Yang, Weijiang
2023-08-10 0:01 ` Paolo Bonzini
2023-08-10 1:12 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 05/19] KVM:x86: Initialize kvm_caps.supported_xss Yang Weijiang
2023-08-04 18:45 ` Sean Christopherson
2023-08-08 15:08 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 06/19] KVM:x86: Load guest FPU state when access XSAVE-managed MSRs Yang Weijiang
2023-08-03 4:27 ` [PATCH v5 07/19] KVM:x86: Add fault checks for guest CR4.CET setting Yang Weijiang
2023-08-03 9:07 ` Chao Gao
2023-08-03 4:27 ` [PATCH v5 08/19] KVM:x86: Report KVM supported CET MSRs as to-be-saved Yang Weijiang
2023-08-03 10:39 ` Chao Gao
2023-08-04 3:13 ` Yang, Weijiang
2023-08-04 5:51 ` Chao Gao
2023-08-04 18:51 ` Sean Christopherson
2023-08-04 22:01 ` Paolo Bonzini
2023-08-08 15:16 ` Yang, Weijiang
2023-08-06 8:54 ` Yang, Weijiang
2023-08-04 18:55 ` Sean Christopherson
2023-08-08 15:26 ` Yang, Weijiang
2023-08-04 21:47 ` Paolo Bonzini
2023-08-09 3:14 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 09/19] KVM:x86: Make guest supervisor states as non-XSAVE managed Yang Weijiang
2023-08-03 11:15 ` Chao Gao
2023-08-04 3:26 ` Yang, Weijiang
2023-08-04 20:45 ` Sean Christopherson
2023-08-04 20:59 ` Peter Zijlstra
2023-08-04 21:32 ` Paolo Bonzini
2023-08-09 2:51 ` Yang, Weijiang
2023-08-09 2:39 ` Yang, Weijiang
2023-08-10 9:29 ` Yang, Weijiang
2023-08-10 14:29 ` Dave Hansen
2023-08-10 15:15 ` Paolo Bonzini
2023-08-10 15:37 ` Sean Christopherson
2023-08-11 3:03 ` Yang, Weijiang
2023-08-28 21:00 ` Dave Hansen
2023-08-29 7:05 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 10/19] KVM:VMX: Introduce CET VMCS fields and control bits Yang Weijiang
2023-08-03 4:27 ` [PATCH v5 11/19] KVM:VMX: Emulate read and write to CET MSRs Yang Weijiang
2023-08-04 5:14 ` Chao Gao
2023-08-04 21:27 ` Sean Christopherson
2023-08-04 21:45 ` Paolo Bonzini
2023-08-04 22:21 ` Sean Christopherson
2023-08-07 7:03 ` Paolo Bonzini
2023-08-06 8:44 ` Yang, Weijiang
2023-08-07 7:00 ` Paolo Bonzini
2023-08-04 8:28 ` Chao Gao
2023-08-09 7:12 ` Yang, Weijiang
2023-08-04 21:40 ` Paolo Bonzini
2023-08-09 3:05 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 12/19] KVM:x86: Save and reload SSP to/from SMRAM Yang Weijiang
2023-08-04 7:53 ` Chao Gao
2023-08-04 15:25 ` Sean Christopherson
2023-08-06 9:14 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 13/19] KVM:VMX: Set up interception for CET MSRs Yang Weijiang
2023-08-04 8:16 ` Chao Gao
2023-08-06 9:22 ` Yang, Weijiang
2023-08-07 1:16 ` Chao Gao
2023-08-09 6:11 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 14/19] KVM:VMX: Set host constant supervisor states to VMCS fields Yang Weijiang
2023-08-04 8:23 ` Chao Gao
2023-08-03 4:27 ` [PATCH v5 15/19] KVM:x86: Optimize CET supervisor SSP save/reload Yang Weijiang
2023-08-04 8:43 ` Chao Gao
2023-08-09 9:00 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 16/19] KVM:x86: Enable CET virtualization for VMX and advertise to userspace Yang Weijiang
2023-08-03 4:27 ` [PATCH v5 17/19] KVM:x86: Enable guest CET supervisor xstate bit support Yang Weijiang
2023-08-04 22:02 ` Paolo Bonzini
2023-08-09 6:07 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 18/19] KVM:nVMX: Refine error code injection to nested VM Yang Weijiang
2023-08-04 21:38 ` Sean Christopherson
2023-08-09 3:00 ` Yang, Weijiang
2023-08-03 4:27 ` [PATCH v5 19/19] KVM:nVMX: Enable CET support for " Yang Weijiang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d888f479-370a-00d3-b929-780e0600dee5@intel.com \
--to=weijiang.yang@intel.com \
--cc=binbin.wu@linux.intel.com \
--cc=chao.gao@intel.com \
--cc=john.allen@amd.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=rick.p.edgecombe@intel.com \
--cc=seanjc@google.com \
--cc=yi.z.zhang@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®