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x86/apic: Implement EIO micro-optimization 

We know both register and value for eoi beforehand,
so there's no need to check it and no need to do math
to calculate the msr. Saves instructions/branches
on each EOI when using x2apic.

I looked at the objdump output to verify that the
generated code looks right and actually is shorter.

The real improvemements will be on the KVM guest side
though, those come in a later patch.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: gleb@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/e019d1a125316f10d3e3a4b2f6bda41473f4fb72.1337184153.git.mst@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Michael S. Tsirkin 2012-05-16 19:03:58 +03:00 committed by Ingo Molnar
parent 2a43195d83
commit 0ab711ae6a
4 changed files with 8 additions and 3 deletions
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5
arch/x86/include/asm/apic.h
View File

@ -138,6 +138,11 @@ static inline void native_apic_msr_write(u32 reg, u32 v)
wrmsr(APIC_BASE_MSR + (reg >> 4), v, 0);
}
static inline void native_apic_msr_eoi_write(u32 reg, u32 v)
{
wrmsr(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
}
static inline u32 native_apic_msr_read(u32 reg)
{
u64 msr;

2
arch/x86/kernel/apic/x2apic_cluster.c
View File

@ -260,7 +260,7 @@ static struct apic apic_x2apic_cluster = {
.read = native_apic_msr_read,
.write = native_apic_msr_write,
.eoi_write = native_apic_msr_write,
.eoi_write = native_apic_msr_eoi_write,
.icr_read = native_x2apic_icr_read,
.icr_write = native_x2apic_icr_write,
.wait_icr_idle = native_x2apic_wait_icr_idle,

2
arch/x86/kernel/apic/x2apic_phys.c
View File

@ -172,7 +172,7 @@ static struct apic apic_x2apic_phys = {
.read = native_apic_msr_read,
.write = native_apic_msr_write,
.eoi_write = native_apic_msr_write,
.eoi_write = native_apic_msr_eoi_write,
.icr_read = native_x2apic_icr_read,
.icr_write = native_x2apic_icr_write,
.wait_icr_idle = native_x2apic_wait_icr_idle,

2
arch/x86/kernel/apic/x2apic_uv_x.c
View File

@ -404,7 +404,7 @@ static struct apic __refdata apic_x2apic_uv_x = {
.read = native_apic_msr_read,
.write = native_apic_msr_write,
.eoi_write = native_apic_msr_write,
.eoi_write = native_apic_msr_eoi_write,
.icr_read = native_x2apic_icr_read,
.icr_write = native_x2apic_icr_write,
.wait_icr_idle = native_x2apic_wait_icr_idle,