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From: Andy Lutomirski <luto@kernel.org>
To: "Bae, Chang Seok" <chang.seok.bae@intel.com>,
	Nadav Amit <namit@vmware.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Lutomirski <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"Metzger, Markus T" <markus.t.metzger@intel.com>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [v3 07/12] x86/fsgsbase/64: Introduce the new FIND_PERCPU_BASE macro
Date: Thu, 25 Oct 2018 17:25:17 -0700	[thread overview]
Message-ID: <CALCETrV-fmLpwsa7tXZ8J+G5PQ6s0yhYVhY3jtE=FP9gAXc+QQ@mail.gmail.com> (raw)
In-Reply-To: <20181023184234.14025-8-chang.seok.bae@intel.com>

On Tue, Oct 23, 2018 at 11:43 AM Chang S. Bae <chang.seok.bae@intel.com> wrote:
>
> GSBASE is used to find per-CPU data in the kernel. But when it is unknown,
> the per-CPU base can be found from the per_cpu_offset table with a CPU NR.
> The CPU NR is extracted from the limit field of the CPUNODE entry in GDT,
> or by the RDPID instruction.
>
> Also, add the GAS-compatible RDPID macro.
>
> The new macro will be used on a following patch.
>
> Suggested-by: H. Peter Anvin <hpa@zytor.com>
> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> ---
>  arch/x86/include/asm/fsgsbase.h | 52 +++++++++++++++++++++++++++++++++
>  arch/x86/include/asm/inst.h     | 15 ++++++++++
>  2 files changed, 67 insertions(+)
>
> diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h
> index e500d771155f..0c2d7d8a8c01 100644
> --- a/arch/x86/include/asm/fsgsbase.h
> +++ b/arch/x86/include/asm/fsgsbase.h
> @@ -111,6 +111,58 @@ extern void x86_gsbase_write_cpu_inactive(unsigned long gsbase);
>         MODRM 0xd0 wrgsbase_opd 1
>  .endm
>
> +#if CONFIG_SMP
> +
> +/*
> + * Fetch the per-CPU GSBASE value for this processor and put it in @reg.
> + * We normally use %gs for accessing per-CPU data, but we are setting up
> + * %gs here and obviously can not use %gs itself to access per-CPU data.
> + */
> +.macro FIND_PERCPU_BASE_RDPID reg:req
> +       /*
> +        * The CPU/node NR is initialized earlier, directly in cpu_init().
P
> +        */
> +       RDPID   \reg

I would suggest that you instead add a macro LOAD_CPU_AND_NODE \reg
and have that macro contain the alternative.  It can switch between
RDPID and LSL.  This way you avoid duplicating the rest of it.

This should end up in the same header as __getcpu() -- it probably
makes sense to just move __getcpu() for this purpose.

Also, hpa and Nadav, shouldn't asm/inst.h end up in macros.S?

--Andy

  reply	other threads:[~2018-10-26  0:25 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-23 18:42 [v3 00/12] x86: Enable FSGSBASE instructions Chang S. Bae
2018-10-23 18:42 ` [v3 01/12] taint: Introduce a new taint flag (insecure) Chang S. Bae
2018-10-24 18:50   ` Andy Lutomirski
2018-10-23 18:42 ` [v3 02/12] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2018-10-24 18:51   ` Andy Lutomirski
2018-10-23 18:42 ` [v3 03/12] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions Chang S. Bae
2018-10-24 18:53   ` Andy Lutomirski
2018-10-24 19:21     ` Andi Kleen
2018-10-25 23:14       ` Andy Lutomirski
2018-10-25 23:31         ` Linus Torvalds
2018-10-26  0:09           ` Andy Lutomirski
2018-10-23 18:42 ` [v3 04/12] x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions Chang S. Bae
2018-10-24 19:16   ` Andy Lutomirski
2018-10-24 19:41     ` [Xen-devel] " Andrew Cooper
2018-10-25  6:09       ` Juergen Gross
2018-10-25 23:08         ` Andrew Cooper
2018-10-25 23:11           ` Andy Lutomirski
2018-10-25 23:14             ` Andrew Cooper
2018-10-25  7:32     ` Bae, Chang Seok
2018-10-25 23:00       ` Andy Lutomirski
2018-10-25 23:03         ` Bae, Chang Seok
2018-10-25 23:16     ` Andy Lutomirski
2018-10-23 18:42 ` [v3 05/12] x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is on Chang S. Bae
2018-10-24 19:21   ` Andy Lutomirski
2018-10-24 19:36     ` Bae, Chang Seok
2018-10-23 18:42 ` [v3 06/12] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available Chang S. Bae
2018-10-23 18:42 ` [v3 07/12] x86/fsgsbase/64: Introduce the new FIND_PERCPU_BASE macro Chang S. Bae
2018-10-26  0:25   ` Andy Lutomirski [this message]
2018-10-26  0:59     ` Nadav Amit
2018-10-23 18:42 ` [v3 08/12] x86/fsgsbase/64: Use the per-CPU base as GSBASE at the paranoid_entry Chang S. Bae
2018-10-23 18:42 ` [v3 09/12] selftests/x86/fsgsbase: Test WRGSBASE Chang S. Bae
2018-10-23 18:42 ` [v3 10/12] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae
2018-10-23 18:42 ` [v3 11/12] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2018-10-23 18:42 ` [v3 12/12] x86/fsgsbase/64: Add documentation for FSGSBASE Chang S. Bae

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