From: Dave Hansen <dave.hansen@intel.com>
To: Uros Bizjak <ubizjak@gmail.com>, Chao Gao <chao.gao@intel.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, tglx@linutronix.de, seanjc@google.com,
pbonzini@redhat.com, peterz@infradead.org,
rick.p.edgecombe@intel.com, weijiang.yang@intel.com,
john.allen@amd.com, bp@alien8.de, chang.seok.bae@intel.com,
xin3.li@intel.com,
Aruna Ramakrishna <aruna.ramakrishna@oracle.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eric Biggers <ebiggers@google.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Kees Cook <kees@kernel.org>, Maxim Levitsky <mlevitsk@redhat.com>,
Mitchell Levy <levymitchell0@gmail.com>,
Nikolay Borisov <nik.borisov@suse.com>,
Oleg Nesterov <oleg@redhat.com>,
Samuel Holland <samuel.holland@sifive.com>,
Sohil Mehta <sohil.mehta@intel.com>,
Stanislav Spassov <stanspas@amazon.de>,
Vignesh Balasubramanian <vigbalas@amd.com>,
Zhao Liu <zhao1.liu@intel.com>
Subject: Re: [PATCH v7 0/6] Introduce CET supervisor state support
Date: Fri, 16 May 2025 08:15:56 -0700 [thread overview]
Message-ID: <ede5efc3-1a6d-45c7-807d-ac83d3de223e@intel.com> (raw)
In-Reply-To: <CAFULd4Y3VvqNS8VEvw0ObnqnVDtsC-q3kDEnyc070=gZ9oehgg@mail.gmail.com>
On 5/16/25 00:51, Uros Bizjak wrote:
> I wonder if the same approach can be used to optimize switching of
> Intel PT configuration context. There was a patch series [1] posted
> some time ago that showed substantial reduction of overhead when
> switching Intel PT configuration context on VM-Entry/Exit using
> XSAVES/XRSTORS instructions:
>
> Manual save(rdmsr): ~334 cycles
> Manual restore(wrmsr): ~1668 cycles
>
> XSAVES insturction: ~124 cycles
> XRSTORS instruction: ~378 cycles
There's nothing stopping us from using XSAVES/XRSTORS for PT,
independent of the kernel FPU infrastructure. RFBM exists for a reason.
There's also WRMSRLIST which we're not using yet either. It's an even
better fit and doesn't have the goofiness that using XSAVE does like the
legacy portion of the save area including the header.
prev parent reply other threads:[~2025-05-16 15:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-12 8:57 Chao Gao
2025-05-12 8:57 ` [PATCH v7 1/6] x86/fpu/xstate: Differentiate default features for host and guest FPUs Chao Gao
2025-05-21 16:49 ` Sean Christopherson
2025-05-22 14:44 ` Chao Gao
2025-05-12 8:57 ` [PATCH v7 2/6] x86/fpu: Initialize guest FPU permissions from guest defaults Chao Gao
2025-05-12 8:57 ` [PATCH v7 3/6] x86/fpu: Initialize guest fpstate and FPU pseudo container " Chao Gao
2025-05-12 14:13 ` Sean Christopherson
2025-05-12 15:21 ` Chao Gao
2025-05-12 8:57 ` [PATCH v7 4/6] x86/fpu: Remove xfd argument from __fpstate_reset() Chao Gao
2025-05-12 8:57 ` [PATCH v7 5/6] x86/fpu/xstate: Introduce "guest-only" supervisor xfeature set Chao Gao
2025-05-12 8:57 ` [PATCH v7 6/6] x86/fpu/xstate: Add CET supervisor xfeature support as a guest-only feature Chao Gao
2025-05-15 15:41 ` [PATCH v7 0/6] Introduce CET supervisor state support Ingo Molnar
2025-05-16 15:19 ` Dave Hansen
2025-05-16 15:20 ` Dave Hansen
2025-05-21 0:22 ` Chao Gao
2025-05-21 16:59 ` Sean Christopherson
2025-05-22 7:51 ` Peter Zijlstra
2025-05-16 7:51 ` Uros Bizjak
2025-05-16 9:02 ` Chao Gao
2025-05-16 15:15 ` Dave Hansen [this message]
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