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From: Dave Hansen <dave.hansen@intel.com>
To: Jim Mattson <jmattson@google.com>
Cc: Borislav Petkov <bp@alien8.de>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
	Jiaxi Chen <jiaxi.chen@linux.intel.com>,
	Kim Phillips <kim.phillips@amd.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] x86: KVM: Add feature flag for AMD's FsGsKernelGsBaseNonSerializing
Date: Thu, 5 Oct 2023 10:52:01 -0700	[thread overview]
Message-ID: <4059e9c6-e85b-085f-b5c5-9da209bbfab2@intel.com> (raw)
In-Reply-To: <CALMp9eQL4m6PVVhntG9-RbY6w60pxka2tpCvTi01dQXPJ7QEJA@mail.gmail.com>

On 10/5/23 09:41, Jim Mattson wrote:
>>
>> But I'm struggling to think of cases where Intel has read-only
>> "defeature bits" like this one.  There are certainly things like
>> MSR_IA32_MISC_ENABLE_FAST_STRING that can be toggled, but read-only
>> indicators of a departure from established architecture seems ...
>> suboptimal.
...
> CPUID.(EAX=7,ECX=0):EBX[bit 13] (Haswell) - "Deprecates FPU CS and FPU
> DS values if 1."
> CPUID.(EAX=7,ECX=0):EBX[bit 6] (Skylake) - "FDP_EXCPTN_ONLY. x87 FPU
> Data Pointer updated only on x87 exceptions if 1."

Thanks!

Trying to group these does make sense to me.  I don't think people take
architecture breakage lightly, but I certainly never considered that it
might, for instance, be important enough to create a new VM migration pool.

I'll try to keep an eye out for these.

  parent reply	other threads:[~2023-10-05 17:52 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-04  0:20 [PATCH] x86: KVM: Add feature flag for AMD's FsGsKernelGsBaseNonSerializing Jim Mattson
2023-10-04  0:57 ` Dave Hansen
2023-10-04  2:44   ` Jim Mattson
2023-10-04  3:27     ` Dave Hansen
2023-10-04  4:24       ` Jim Mattson
2023-10-04  7:58     ` Borislav Petkov
2023-10-04 20:29       ` Jim Mattson
2023-10-05 16:22       ` Jim Mattson
2023-10-05 16:35         ` Dave Hansen
2023-10-05 16:41           ` Jim Mattson
2023-10-05 16:51             ` Paolo Bonzini
2023-10-05 17:52             ` Dave Hansen [this message]
2023-10-05 16:38       ` Paolo Bonzini
2023-10-05 17:06         ` Jim Mattson
2023-10-05 17:14           ` Paolo Bonzini
2023-10-05 17:27             ` Jim Mattson

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