# HG changeset patch
# User Hollis Blanchard <hollisb@xxxxxxxxxx>
# Date 1217011851 18000
# Node ID 1971b4293f12f227a61828d536f6e3b106d1a60c
# Parent 323134066eeafb9e5258b74d05935447ffdf90f1
kvm: ppc: Stop saving host TLB state.
We're saving the host TLB state to memory on every exit, but never using it.
Originally I had thought that we'd want to restore host TLB for heavyweight
exits, but that could actually hurt when context switching to an unrelated host
process (i.e. not qemu).
Since this decreases the performance penalty of all exits, this patch improves
guest boot time by about 15%.
Signed-off-by: Hollis Blanchard <hollisb@xxxxxxxxxx>
---
3 files changed, 3 insertions(+), 17 deletions(-)
arch/powerpc/kernel/asm-offsets.c | 1 -
arch/powerpc/kvm/booke_interrupts.S | 17 +++--------------
include/asm-powerpc/kvm_host.h | 2 --
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -356,7 +356,6 @@ int main(void)
DEFINE(VCPU_HOST_STACK, offsetof(struct kvm_vcpu, arch.host_stack));
DEFINE(VCPU_HOST_PID, offsetof(struct kvm_vcpu, arch.host_pid));
- DEFINE(VCPU_HOST_TLB, offsetof(struct kvm_vcpu, arch.host_tlb));
DEFINE(VCPU_SHADOW_TLB, offsetof(struct kvm_vcpu, arch.shadow_tlb));
DEFINE(VCPU_GPRS, offsetof(struct kvm_vcpu, arch.gpr));
DEFINE(VCPU_LR, offsetof(struct kvm_vcpu, arch.lr));
diff --git a/arch/powerpc/kvm/booke_interrupts.S b/arch/powerpc/kvm/booke_interrupts.S
--- a/arch/powerpc/kvm/booke_interrupts.S
+++ b/arch/powerpc/kvm/booke_interrupts.S
@@ -342,26 +342,15 @@ lightweight_exit:
andc r6, r5, r6
mtmsr r6
- /* Save the host's non-pinned TLB mappings, and load the guest mappings
- * over them. Leave the host's "pinned" kernel mappings in place. */
- /* XXX optimization: use generation count to avoid swapping unmodified
- * entries. */
+ /* Load the guest mappings, leaving the host's "pinned" kernel mappings
+ * in place. */
+ /* XXX optimization: load only modified guest entries. */
mfspr r10, SPRN_MMUCR /* Save host MMUCR. */
lis r8, tlb_44x_hwater@ha
lwz r8, tlb_44x_hwater@l(r8)
- addi r3, r4, VCPU_HOST_TLB - 4
addi r9, r4, VCPU_SHADOW_TLB - 4
li r6, 0
1:
- /* Save host entry. */
- tlbre r7, r6, PPC44x_TLB_PAGEID
- mfspr r5, SPRN_MMUCR
- stwu r5, 4(r3)
- stwu r7, 4(r3)
- tlbre r7, r6, PPC44x_TLB_XLAT
- stwu r7, 4(r3)
- tlbre r7, r6, PPC44x_TLB_ATTRIB
- stwu r7, 4(r3)
/* Load guest entry. */
lwzu r7, 4(r9)
mtspr SPRN_MMUCR, r7
diff --git a/include/asm-powerpc/kvm_host.h b/include/asm-powerpc/kvm_host.h
--- a/include/asm-powerpc/kvm_host.h
+++ b/include/asm-powerpc/kvm_host.h
@@ -81,8 +81,6 @@ struct kvm_vcpu_arch {
struct tlbe shadow_tlb[PPC44x_TLB_SIZE];
/* Pages which are referenced in the shadow TLB. */
struct page *shadow_pages[PPC44x_TLB_SIZE];
- /* Copy of the host's TLB. */
- struct tlbe host_tlb[PPC44x_TLB_SIZE];
u32 host_stack;
u32 host_pid;
--
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