From: "H. Peter Anvin" <hpa@zytor.com>
To: Sean Christopherson <seanjc@google.com>,
"Chang S. Bae" <chang.seok.bae@intel.com>
Cc: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org,
aruna.ramakrishna@oracle.com, pbonzini@redhat.com,
levymitchell0@gmail.com, attofari@amazon.de,
linux-kernel@vger.kernel.org, CobeChen@zhaoxin.com,
TimGuo@zhaoxin.com, LeoLiu-oc@zhaoxin.com,
Lyle Li <LyleLi@zhaoxin.com>
Subject: Re: [PATCH] x86/fpu: Fix the os panic issue caused by the XGETBV instruction
Date: Fri, 17 Jan 2025 19:13:42 -0800 [thread overview]
Message-ID: <1c2e3700-5663-4e6e-9da9-500b64e778a2@zytor.com> (raw)
In-Reply-To: <Z4rVORZR2mBoRqjl@google.com>
On 1/17/25 14:10, Sean Christopherson wrote:
>>
>> Note that XFD is already listed as dependent on XGETBV1.
>>
>> But I doubt the kernel needs to be resilient to deliberately misconfigured
>> or crazy virtual machine setups.
>
> I don't see anything in the SDM that suggests this is a misconfigured CPU. Intel
> might not have plans to ship such CPUs, but AFAICT it's not a violation of the
> architecture as defined in the SDM.
>
> The SDM even explicitly says that protection keys can exist and be used without
> PKU state being supported in XSAVE at all, at which point assuming the existence
> of XGETBV1 is rather nonsensical.
>
Whether or not a combination is *possible* at all is totally separate
from whether or not it is worth for Linux to support it. The CPUID
dependency list exists for exactly that reason -- it defines *Linux
policy* with regards to feature dependencies.
-hpa
prev parent reply other threads:[~2025-01-18 3:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-02 7:54 Tony W Wang-oc
2025-01-15 18:39 ` Chang S. Bae
2025-01-17 22:10 ` Sean Christopherson
2025-01-17 23:24 ` Chang S. Bae
2025-01-18 3:13 ` H. Peter Anvin [this message]
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