Messages in this thread | | | From | Jürgen Groß <> | Subject | Re: [PATCH 4/4] x86/xen: drop USERGS_SYSRET64 paravirt call | Date | Tue, 17 Nov 2020 09:19:17 +0100 |
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On 16.11.20 17:28, Andy Lutomirski wrote: > On Mon, Nov 16, 2020 at 7:23 AM Juergen Gross <jgross@suse.com> wrote: >> >> USERGS_SYSRET64 is used to return from a syscall via sysret, but >> a Xen PV guest will nevertheless use the iret hypercall, as there >> is no sysret PV hypercall defined. >> >> So instead of testing all the prerequisites for doing a sysret and >> then mangling the stack for Xen PV again for doing an iret just use >> the iret exit from the beginning. >> >> This can easily be done via an ALTERNATIVE like it is done for the >> sysenter compat case already. >> >> While at it remove to stale sysret32 remnants. >> >> Signed-off-by: Juergen Gross <jgross@suse.com> > > Acked-by: Andy Lutomirski <luto@kernel.org> > > FWIW, you've lost the VGCF_in_syscall optimization. Let me see if I > can give it back to you better.
Ah, right.
Nevertheless a simple kernel build is about 0.5% faster with this patch.
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |