From: "Yang, Weijiang" <weijiang.yang@intel.com>
To: Chao Gao <chao.gao@intel.com>
Cc: <seanjc@google.com>, <pbonzini@redhat.com>,
<dave.hansen@intel.com>, <x86@kernel.org>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <peterz@infradead.org>,
<rick.p.edgecombe@intel.com>, <mlevitsk@redhat.com>,
<john.allen@amd.com>
Subject: Re: [PATCH v10 10/27] KVM: x86: Refine xsave-managed guest register/MSR reset handling
Date: Tue, 20 Feb 2024 21:23:01 +0800 [thread overview]
Message-ID: <119db925-4472-4070-adb3-767f2bd00726@intel.com> (raw)
In-Reply-To: <ZdQWu3D3Jku1iAvd@chao-email>
On 2/20/2024 11:04 AM, Chao Gao wrote:
> On Sun, Feb 18, 2024 at 11:47:16PM -0800, Yang Weijiang wrote:
>> Tweak the code a bit to facilitate resetting more xstate components in
>> the future, e.g., CET's xstate-managed MSRs.
>>
>> No functional change intended.
> Strictly speaking, there is a functional change. in the previous logic, if
> either of BNDCSR or BNDREGS state is not supported (kvm_mpx_supported() will
> return false), KVM won't reset either of them.
> Since this gets changed, I vote
> to drop 'No functional change ..'
Yes, I'll remove it since existing logic is slightly changed.
>> Suggested-by: Chao Gao <chao.gao@intel.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
>> ---
>> arch/x86/kvm/x86.c | 30 +++++++++++++++++++++++++++---
>> 1 file changed, 27 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 10847e1cc413..5a9c07751c0e 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -12217,11 +12217,27 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
>> static_branch_dec(&kvm_has_noapic_vcpu);
>> }
>>
>> +#define XSTATE_NEED_RESET_MASK (XFEATURE_MASK_BNDREGS | \
>> + XFEATURE_MASK_BNDCSR)
>> +
>> +static bool kvm_vcpu_has_xstate(unsigned long xfeature)
> kvm_vcpu_has_xstate is a misnomer because it doesn't take a vCPU.
True, I'll change it, thanks!
>> +{
>> + switch (xfeature) {
>> + case XFEATURE_MASK_BNDREGS:
>> + case XFEATURE_MASK_BNDCSR:
>> + return kvm_cpu_cap_has(X86_FEATURE_MPX);
>> + default:
>> + return false;
>> + }
>> +}
>> +
>> void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>> {
>> struct kvm_cpuid_entry2 *cpuid_0x1;
>> unsigned long old_cr0 = kvm_read_cr0(vcpu);
>> + DECLARE_BITMAP(reset_mask, 64);
>> unsigned long new_cr0;
>> + unsigned int i;
>>
>> /*
>> * Several of the "set" flows, e.g. ->set_cr0(), read other registers
>> @@ -12274,7 +12290,12 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>> kvm_async_pf_hash_reset(vcpu);
>> vcpu->arch.apf.halted = false;
>>
>> - if (vcpu->arch.guest_fpu.fpstate && kvm_mpx_supported()) {
>> + bitmap_from_u64(reset_mask, (kvm_caps.supported_xcr0 |
>> + kvm_caps.supported_xss) &
>> + XSTATE_NEED_RESET_MASK);
>> +
>> + if (vcpu->arch.guest_fpu.fpstate &&
>> + !bitmap_empty(reset_mask, XFEATURE_MAX)) {
>> struct fpstate *fpstate = vcpu->arch.guest_fpu.fpstate;
>>
>> /*
>> @@ -12284,8 +12305,11 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>> if (init_event)
>> kvm_put_guest_fpu(vcpu);
>>
>> - fpstate_clear_xstate_component(fpstate, XFEATURE_BNDREGS);
>> - fpstate_clear_xstate_component(fpstate, XFEATURE_BNDCSR);
>> + for_each_set_bit(i, reset_mask, XFEATURE_MAX) {
>> + if (!kvm_vcpu_has_xstate(i))
>> + continue;
> The kvm_vcpu_has_xstate() check is superfluous because @i is derived from
> kvm_caps.supported_xcr0/xss, which already guarantees that all unsupported
> xfeatures are filtered out.
Yeah, at least currently I can skip the check for CET/MPX feaures, will remove it, thanks!
>
> I recommend dropping this check. w/ this change,
>
> Reviewed-by: Chao Gao <chao.gao@intel.com>
>
>> + fpstate_clear_xstate_component(fpstate, i);
>> + }
>>
>> if (init_event)
>> kvm_load_guest_fpu(vcpu);
>> --
>> 2.43.0
>>
next prev parent reply other threads:[~2024-02-20 13:23 UTC|newest]
Thread overview: 94+ 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 [this message]
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
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
2024-05-22 9:03 ` Yang, Weijiang
2024-05-22 15:06 ` Edgecombe, Rick P
2024-05-23 10:07 ` Yang, Weijiang
2024-05-22 8:41 ` Yang, Weijiang
2024-05-27 9:05 ` Yang, Weijiang
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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