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| author | Boris Ostrovsky <boris.ostrovsky@oracle.com> | 2015-11-20 00:55:45 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-11-23 12:48:16 +0300 |
| commit | 5fdf5d37f40a3b18c0d613463867f71c017b75ef (patch) | |
| tree | 7f951152baafdced8f6b80e047463a2208c217f5 /arch/x86/entry/entry_64_compat.S | |
| parent | 1ec218373b8ebda821aec00bb156a9c94fad9cd4 (diff) | |
| download | linux-5fdf5d37f40a3b18c0d613463867f71c017b75ef.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>
Diffstat (limited to 'arch/x86/entry/entry_64_compat.S')
| -rw-r--r-- | arch/x86/entry/entry_64_compat.S | 10 |
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: |