Commit Graph

4 Commits

Author SHA1 Message Date
Jeremy Fitzhardinge 41edafdb78 x86/pvops: add a paravirt_ident functions to allow special patching
Impact: Optimization

Several paravirt ops implementations simply return their arguments,
the most obvious being the make_pte/pte_val class of operations on
native.

On 32-bit, the identity function is literally a no-op, as the calling
convention uses the same registers for the first argument and return.
On 64-bit, it can be implemented with a single "mov".

This patch adds special identity functions for 32 and 64 bit argument,
and machinery to recognize them and replace them with either nops or a
mov as appropriate.

At the moment, the only users for the identity functions are the
pagetable entry conversion functions.

The result is a measureable improvement on pagetable-heavy benchmarks
(2-3%, reducing the pvops overhead from 5 to 2%).

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2009-01-30 14:51:44 -08:00
Paolo Ciarrocchi d9336a9b47 x86: coding style fixes to arch/x86/kernel/paravirt_patch_32.c
Before:
total: 3 errors, 1 warnings, 49 lines checked

After:
total: 2 errors, 1 warnings, 49 lines checked

paolo@paolo-desktop:~/linux.trees.git$ md5sum /tmp/paravirt_patch_32.o.*
a78eea4264723e18c49dcfbe0ee0aae7  /tmp/paravirt_patch_32.o.after
a78eea4264723e18c49dcfbe0ee0aae7  /tmp/paravirt_patch_32.o.before

Signed-off-by: Paolo Ciarrocchi <paolo.ciarrocchi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-08-15 16:53:25 +02:00
Jeremy Fitzhardinge d75cd22fdd x86/paravirt: split sysret and sysexit
Don't conflate sysret and sysexit; they're different instructions with
different semantics, and may be in use at the same time (at least
within the same kernel, depending on whether its an Intel or AMD
system).

sysexit - just return to userspace, does no register restoration of
    any kind; must explicitly atomically enable interrupts.

sysret - reloads flags from r11, so no need to explicitly enable
    interrupts on 64-bit, responsible for restoring usermode %gs

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citirx.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-08 13:13:15 +02:00
Glauber de Oliveira Costa 2f485ef568 x86: move patching code to arch-specific file.
The core patching code for paravirt is sufficiently different
among i386 and x86_64, and we move them to specific files.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30 13:32:10 +01:00