From 7924bd41097ae8991c6d38cef8b1e4058e30d198 Mon Sep 17 00:00:00 2001 From: Hollis Blanchard Date: Tue, 2 Dec 2008 15:51:55 -0600 Subject: KVM: ppc: directly insert shadow mappings into the hardware TLB Formerly, we used to maintain a per-vcpu shadow TLB and on every entry to the guest would load this array into the hardware TLB. This consumed 1280 bytes of memory (64 entries of 16 bytes plus a struct page pointer each), and also required some assembly to loop over the array on every entry. Instead of saving a copy in memory, we can just store shadow mappings directly into the hardware TLB, accepting that the host kernel will clobber these as part of the normal 440 TLB round robin. When we do that we need less than half the memory, and we have decreased the exit handling time for all guest exits, at the cost of increased number of TLB misses because the host overwrites some guest entries. These savings will be increased on processors with larger TLBs or which implement intelligent flush instructions like tlbivax (which will avoid the need to walk arrays in software). In addition to that and to the code simplification, we have a greater chance of leaving other host userspace mappings in the TLB, instead of forcing all subsequent tasks to re-fault all their mappings. Signed-off-by: Hollis Blanchard Signed-off-by: Avi Kivity --- arch/powerpc/kernel/asm-offsets.c | 6 ------ 1 file changed, 6 deletions(-) (limited to 'arch/powerpc/kernel') diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 393c7f36a1e..ba39526d320 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -359,12 +359,6 @@ int main(void) #ifdef CONFIG_KVM DEFINE(TLBE_BYTES, sizeof(struct kvmppc_44x_tlbe)); - DEFINE(VCPU_TO_44X, offsetof(struct kvmppc_vcpu_44x, vcpu)); - DEFINE(VCPU44x_SHADOW_TLB, - offsetof(struct kvmppc_vcpu_44x, shadow_tlb)); - DEFINE(VCPU44x_SHADOW_MOD, - offsetof(struct kvmppc_vcpu_44x, shadow_tlb_mod)); - DEFINE(VCPU_HOST_STACK, offsetof(struct kvm_vcpu, arch.host_stack)); DEFINE(VCPU_HOST_PID, offsetof(struct kvm_vcpu, arch.host_pid)); DEFINE(VCPU_GPRS, offsetof(struct kvm_vcpu, arch.gpr)); -- cgit v1.2.3-70-g09d2