>So on user space to kernel space transitions swapping in kernel GS should
>simply do:
> userGS = RDGSBASE()
> WRGSBASE(kernelGS)
This would also need to find kernelGS first, by doing RDPID and then
reading it from memory in the right index
(which might be a full cache miss if y
On Mon, 25 Mar 2019, Thomas Gleixner wrote:
> On Mon, 25 Mar 2019, Thomas Gleixner wrote:
> > The whole point of FSGSBASE support is performance, right?
> >
> > So can please someone explain why having the following in the context
> > switch path when it can be completely avoided is enhancing per
On Mon, 25 Mar 2019, Thomas Gleixner wrote:
> The whole point of FSGSBASE support is performance, right?
>
> So can please someone explain why having the following in the context
> switch path when it can be completely avoided is enhancing performance:
>
> - 4 x SWAPGS
> - 1 x RDMSR
> - 1 x
On Fri, 15 Mar 2019, Chang S. Bae wrote:
> The helper functions will switch on faster accesses to FSBASE and GSBASE
> when the FSGSBASE feature is enabled.
>
> Accessing user GSBASE needs a couple of SWAPGS operations. It is avoidable
> if the user GSBASE is saved at kernel entry, being updated a
The helper functions will switch on faster accesses to FSBASE and GSBASE
when the FSGSBASE feature is enabled.
Accessing user GSBASE needs a couple of SWAPGS operations. It is avoidable
if the user GSBASE is saved at kernel entry, being updated as changes, and
restored back at kernel exit. However
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