From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Xin Li <xin3.li@intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
hpa@zytor.com, brgerst@gmail.com, chang.seok.bae@intel.com,
jgross@suse.com
Subject: Re: [PATCH v6 0/5] x86: Enable LKGS instruction
Date: Thu, 12 Jan 2023 15:57:15 +0100 [thread overview]
Message-ID: <Y8Afy2J0io8F510i@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <Y7/5YPxbRE2AWgT0@gmail.com>
On Thu, Jan 12, 2023 at 01:13:20PM +0100, Ingo Molnar wrote:
>
> * Xin Li <xin3.li@intel.com> wrote:
>
> > LKGS instruction is introduced with Intel FRED (flexible return and event
> > delivery) specification. As LKGS is independent of FRED, we enable it as
> > a standalone CPU feature.
> >
> > LKGS behaves like the MOV to GS instruction except that it loads the base
> > address into the IA32_KERNEL_GS_BASE MSR instead of the GS segment’s
> > descriptor cache, which is exactly what Linux kernel does to load user
> > level GS base. Thus, with LKGS, there is no need to SWAPGS away from the
> > kernel GS base.
>
> Ok, this looks good to me.
>
> I've applied the first 4 patches to tip:x86/cpu, as the instruction exists
> in a public document and these patches are fine stand-alone as well, such
> as the factoring out of load_gs_index() methods from a high-use low level
> header into a new header file.
>
> Planning to apply the final, LKGS enabler patch as well, unless there's any
> objections from others?
Nah, I think that thing's bike-shedded to near death. Let's just do it.
next prev parent reply other threads:[~2023-01-12 15:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-12 7:20 [PATCH v6 0/5] x86: Enable LKGS instruction Xin Li
2023-01-12 7:20 ` [PATCH v6 1/5] x86/cpufeature: add the cpu feature bit for LKGS Xin Li
2023-01-12 12:16 ` [tip: x86/cpu] x86/cpufeature: Add the CPU " tip-bot2 for H. Peter Anvin (Intel)
2023-01-12 7:20 ` [PATCH v6 2/5] x86/opcode: add the LKGS instruction to x86-opcode-map Xin Li
2023-01-12 12:16 ` [tip: x86/cpu] x86/opcode: Add " tip-bot2 for H. Peter Anvin (Intel)
2023-01-12 7:20 ` [PATCH v6 3/5] x86/gsseg: make asm_load_gs_index() take an u16 Xin Li
2023-01-12 12:16 ` [tip: x86/cpu] x86/gsseg: Make " tip-bot2 for H. Peter Anvin (Intel)
2023-01-12 7:20 ` [PATCH v6 4/5] x86/gsseg: move load_gs_index() to its own new header file Xin Li
2023-01-12 12:16 ` [tip: x86/cpu] x86/gsseg: Move " tip-bot2 for H. Peter Anvin (Intel)
2023-01-12 7:20 ` [PATCH v6 5/5] x86/gsseg: use the LKGS instruction if available for load_gs_index() Xin Li
2023-01-13 9:36 ` [tip: x86/cpu] x86/gsseg: Use " tip-bot2 for H. Peter Anvin (Intel)
2023-01-12 12:13 ` [PATCH v6 0/5] x86: Enable LKGS instruction Ingo Molnar
2023-01-12 14:57 ` Peter Zijlstra [this message]
2023-01-13 13:29 ` Ingo Molnar
2023-01-13 18:26 ` Li, Xin3
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