Re: [PATCH v12 00/18] Enable FSGSBASE instructions

From: Sasha Levin
Date: Mon May 18 2020 - 08:34:03 EST


On Sun, May 17, 2020 at 11:18:36PM -0700, Christoph Hellwig wrote:
On Mon, May 11, 2020 at 12:52:53AM -0400, Sasha Levin wrote:
Benefits:
Currently a user process that wishes to read or write the FS/GS base must
make a system call. But recent X86 processors have added new instructions
for use in 64-bit mode that allow direct access to the FS and GS segment
base addresses. The operating system controls whether applications can
use these instructions with a %cr4 control bit.

In addition to benefits to applications, performance improvements to the
OS context switch code are possible by making use of these instructions. A
third party reported out promising performance numbers out of their
initial benchmarking of the previous version of this patch series [9].

The [9] reference can't be resolved anywhere in this mail.

Sorry, I'll fix it up. The reference was supposed to be pointing to:

https://www.phoronix.com/scan.php?page=article&item=linux-wip-fsgsbase&num=1

--
Thanks,
Sasha