From 91e2eea98f94a2ebb143d4c4cdeaa4573d62dc17 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Thu, 19 Nov 2015 16:55:45 -0500 Subject: x86/xen: Avoid fast syscall path for Xen PV guests After 32-bit syscall rewrite, and specifically after commit: 5f310f739b4c ("x86/entry/32: Re-implement SYSENTER using the new C path") ... the stack frame that is passed to xen_sysexit is no longer a "standard" one (i.e. it's not pt_regs). Since we end up calling xen_iret from xen_sysexit we don't need to fix up the stack and instead follow entry_SYSENTER_32's IRET path directly to xen_iret. We can do the same thing for compat mode even though stack does not need to be fixed. This will allow us to drop usergs_sysret32 paravirt op (in the subsequent patch) Suggested-by: Andy Lutomirski Signed-off-by: Boris Ostrovsky Reviewed-by: Borislav Petkov Acked-by: Andy Lutomirski Cc: Andrew Morton Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: david.vrabel@citrix.com Cc: konrad.wilk@oracle.com Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1447970147-1733-2-git-send-email-boris.ostrovsky@oracle.com Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/cpufeature.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/include/asm/cpufeature.h') diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index e4f8010f22e0..f7ba9fbf12ee 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -216,6 +216,7 @@ #define X86_FEATURE_PAUSEFILTER ( 8*32+13) /* AMD filtered pause intercept */ #define X86_FEATURE_PFTHRESHOLD ( 8*32+14) /* AMD pause filter threshold */ #define X86_FEATURE_VMMCALL ( 8*32+15) /* Prefer vmmcall to vmcall */ +#define X86_FEATURE_XENPV ( 8*32+16) /* "" Xen paravirtual guest */ /* Intel-defined CPU features, CPUID level 0x00000007:0 (ebx), word 9 */ -- cgit v1.2.3