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authorBoris Ostrovsky <boris.ostrovsky@oracle.com>2015-11-20 00:55:45 +0300
committerThomas Gleixner <tglx@linutronix.de>2015-12-19 11:55:52 +0300
commit91e2eea98f94a2ebb143d4c4cdeaa4573d62dc17 (patch)
tree87d864fc79de97b94589f5be731c6b7dbb270f7c /arch/x86/entry/entry_64_compat.S
parentd90167a941f62860f35eb960e1012aa2d30e7e94 (diff)
downloadlinux-91e2eea98f94a2ebb143d4c4cdeaa4573d62dc17.tar.xz
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 <luto@amacapital.net> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Reviewed-by: Borislav Petkov <bp@suse.de> Acked-by: Andy Lutomirski <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> 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 <mingo@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/entry/entry_64_compat.S')
-rw-r--r--arch/x86/entry/entry_64_compat.S10
1 files changed, 6 insertions, 4 deletions
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index c3201830a85e..402e34a21559 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -121,8 +121,9 @@ sysenter_flags_fixed:
movq %rsp, %rdi
call do_fast_syscall_32
- testl %eax, %eax
- jz .Lsyscall_32_done
+ /* XEN PV guests always use IRET path */
+ ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
+ "jmp .Lsyscall_32_done", X86_FEATURE_XENPV
jmp sysret32_from_system_call
sysenter_fix_flags:
@@ -200,8 +201,9 @@ ENTRY(entry_SYSCALL_compat)
movq %rsp, %rdi
call do_fast_syscall_32
- testl %eax, %eax
- jz .Lsyscall_32_done
+ /* XEN PV guests always use IRET path */
+ ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
+ "jmp .Lsyscall_32_done", X86_FEATURE_XENPV
/* Opportunistic SYSRET */
sysret32_from_system_call: