linux-toradex.git/arch/x86/kernel/paravirt_patch_64.c, branch v3.0.44

x86/pvops: add a paravirt_ident functions to allow special patching

2009-01-30T22:51:44+00:00

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 
Signed-off-by: H. Peter Anvin

x86/paravirt: add sysret/sysexit pvops for returning to 32-bit compatibility userspace

2008-07-08T11:15:52+00:00

In a 64-bit system, we need separate sysret/sysexit operations to
return to a 32-bit userspace.

Signed-off-by: Jeremy Fitzhardinge 
Cc: xen-devel 
Cc: Stephen Tweedie 
Cc: Eduardo Habkost 
Cc: Mark McLoughlin 
Signed-off-by: Ingo Molnar

x86/paravirt, 64-bit: don't restore user rsp within sysret

2008-07-08T11:13:37+00:00

There's no need to combine restoring the user rsp within the sysret
pvop, so split it out.  This makes the pvop's semantics closer to the
machine instruction.

Signed-off-by: Jeremy Fitzhardinge 
Cc: xen-devel 
Cc: Stephen Tweedie 
Cc: Eduardo Habkost 
Cc: Mark McLoughlin 
Signed-off-by: Ingo Molnar

x86/paravirt: split sysret and sysexit

2008-07-08T11:13:15+00:00

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 
Cc: xen-devel 
Cc: Stephen Tweedie 
Cc: Eduardo Habkost 
Cc: Mark McLoughlin 
Signed-off-by: Ingo Molnar

x86: add stringify header

2008-01-30T12:33:19+00:00

We use a __stringify construction at paravirt_patch_64.c.
It's better practice to include the stringify header directly

Signed-off-by: Glauber de Oliveira Costa 
Signed-off-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner

x86: patching functions on 64-bit

2008-01-30T12:32:10+00:00

Like i386, x86_64 also need to include its own patching function.
(Well, if you're not in a hurry, and don't care about speed, you don't
really _need_ ;-))

So here they are. Not much different in essence from i386

Signed-off-by: Glauber de Oliveira Costa 
Signed-off-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner