From afd30525a659ac0ae0904f0cb4a2ca75522c3123 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Wed, 20 Jan 2021 14:55:45 +0100 Subject: 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 Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20210120135555.32594-6-jgross@suse.com --- arch/x86/kernel/paravirt.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'arch/x86/kernel/paravirt.c') diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index 5e5fcf5c376d..18560b71e717 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -135,8 +135,7 @@ unsigned paravirt_patch_default(u8 type, void *insn_buff, else if (opfunc == _paravirt_ident_64) ret = paravirt_patch_ident_64(insn_buff, len); - else if (type == PARAVIRT_PATCH(cpu.iret) || - type == PARAVIRT_PATCH(cpu.usergs_sysret64)) + else if (type == PARAVIRT_PATCH(cpu.iret)) /* If operation requires a jmp, then jmp */ ret = paravirt_patch_jmp(insn_buff, opfunc, addr, len); #endif @@ -170,7 +169,6 @@ static u64 native_steal_clock(int cpu) /* These are in entry.S */ extern void native_iret(void); -extern void native_usergs_sysret64(void); static struct resource reserve_ioports = { .start = 0, @@ -310,7 +308,6 @@ struct paravirt_patch_template pv_ops = { .cpu.load_sp0 = native_load_sp0, - .cpu.usergs_sysret64 = native_usergs_sysret64, .cpu.iret = native_iret, #ifdef CONFIG_X86_IOPL_IOPERM -- cgit v1.2.3