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Date: Tue, 20 Feb 2024 16:51:04 +0800 From: Chao Gao <chao.gao@...el.com> To: Yang Weijiang <weijiang.yang@...el.com> CC: <seanjc@...gle.com>, <pbonzini@...hat.com>, <dave.hansen@...el.com>, <x86@...nel.org>, <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <peterz@...radead.org>, <rick.p.edgecombe@...el.com>, <mlevitsk@...hat.com>, <john.allen@....com>, Zhang Yi Z <yi.z.zhang@...ux.intel.com> Subject: Re: [PATCH v10 13/27] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS On Sun, Feb 18, 2024 at 11:47:19PM -0800, Yang Weijiang wrote: >Update CPUID.(EAX=0DH,ECX=1).EBX to reflect current required xstate size >due to XSS MSR modification. >CPUID(EAX=0DH,ECX=1).EBX reports the required storage size of all enabled >xstate features in (XCR0 | IA32_XSS). The CPUID value can be used by guest >before allocate sufficient xsave buffer. > >Note, KVM does not yet support any XSS based features, i.e. supported_xss >is guaranteed to be zero at this time. > >Opportunistically modify XSS write access logic as: >If XSAVES is not enabled in the guest CPUID, forbid setting IA32_XSS msr >to anything but 0, even if the write is host initiated. > >Suggested-by: Sean Christopherson <seanjc@...gle.com> >Co-developed-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com> >Signed-off-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com> >Signed-off-by: Yang Weijiang <weijiang.yang@...el.com> >Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com> Reviewed-by: Chao Gao <chao.gao@...el.com>
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