diff options
| author | Juergen Gross <jgross@suse.com> | 2021-01-20 14:55:45 +0100 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-02-10 12:32:07 +0100 |
| commit | afd30525a659ac0ae0904f0cb4a2ca75522c3123 (patch) | |
| tree | ce45cda82fac21a848509aa29661353e634d45d6 /arch/x86/xen/xen-asm.S | |
| parent | x86/pv: Switch SWAPGS to ALTERNATIVE (diff) | |
| download | linux-afd30525a659ac0ae0904f0cb4a2ca75522c3123.tar.xz linux-afd30525a659ac0ae0904f0cb4a2ca75522c3123.zip | |
x86/xen: Drop USERGS_SYSRET64 paravirt call
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.
It should be noted that this drops the optimization in Xen for not
restoring a few registers when returning to user mode, but it seems
as if the saved instructions in the kernel more than compensate for
this drop (a kernel build in a Xen PV guest was slightly faster with
this patch applied).
While at it remove the stale sysret32 remnants.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210120135555.32594-6-jgross@suse.com
Diffstat (limited to 'arch/x86/xen/xen-asm.S')
| -rw-r--r-- | arch/x86/xen/xen-asm.S | 20 |
1 files changed, 0 insertions, 20 deletions
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S index eac9dac3656a..1d738c5957f5 100644 --- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -215,26 +215,6 @@ SYM_CODE_START(xen_iret) jmp hypercall_iret SYM_CODE_END(xen_iret) -SYM_CODE_START(xen_sysret64) - /* - * We're already on the usermode stack at this point, but - * still with the kernel gs, so we can easily switch back. - * - * tss.sp2 is scratch space. - */ - movq %rsp, PER_CPU_VAR(cpu_tss_rw + TSS_sp2) - movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp - - pushq $__USER_DS - pushq PER_CPU_VAR(cpu_tss_rw + TSS_sp2) - pushq %r11 - pushq $__USER_CS - pushq %rcx - - pushq $VGCF_in_syscall - jmp hypercall_iret -SYM_CODE_END(xen_sysret64) - /* * Xen handles syscall callbacks much like ordinary exceptions, which * means we have: |