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Subject[PATCH 28/40] KVM: ppc: Write only modified shadow entries into the TLB on exit
Date
From: Hollis Blanchard <hollisb@us.ibm.com>

Track which TLB entries need to be written, instead of overwriting everything
below the high water mark. Typically only a single guest TLB entry will be
modified in a single exit.

Guest boot time performance improvement: about 15%.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
arch/powerpc/include/asm/kvm_host.h | 3 ++
arch/powerpc/include/asm/kvm_ppc.h | 3 ++
arch/powerpc/kernel/asm-offsets.c | 1 +
arch/powerpc/kvm/44x_tlb.c | 9 +++++-
arch/powerpc/kvm/booke_interrupts.S | 51 +++++++++++++++++++++++-----------
arch/powerpc/kvm/powerpc.c | 15 ++++++++++
6 files changed, 64 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index dc3a756..4338b03 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -82,6 +82,9 @@ struct kvm_vcpu_arch {
/* Pages which are referenced in the shadow TLB. */
struct page *shadow_pages[PPC44x_TLB_SIZE];

+ /* Track which TLB entries we've modified in the current exit. */
+ u8 shadow_tlb_mod[PPC44x_TLB_SIZE];
+
u32 host_stack;
u32 host_pid;
u32 host_dbcr0;
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index a8b0687..8e7e429 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -65,6 +65,9 @@ extern void kvmppc_mmu_invalidate(struct kvm_vcpu *vcpu, gva_t eaddr,
gva_t eend, u32 asid);
extern void kvmppc_mmu_priv_switch(struct kvm_vcpu *vcpu, int usermode);

+/* XXX Book E specific */
+extern void kvmppc_tlbe_set_modified(struct kvm_vcpu *vcpu, unsigned int i);
+
extern void kvmppc_check_and_deliver_interrupts(struct kvm_vcpu *vcpu);

static inline void kvmppc_queue_exception(struct kvm_vcpu *vcpu, int exception)
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 5940649..1631d67 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -357,6 +357,7 @@ 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_SHADOW_TLB, offsetof(struct kvm_vcpu, arch.shadow_tlb));
+ DEFINE(VCPU_SHADOW_MOD, offsetof(struct kvm_vcpu, arch.shadow_tlb_mod));
DEFINE(VCPU_GPRS, offsetof(struct kvm_vcpu, arch.gpr));
DEFINE(VCPU_LR, offsetof(struct kvm_vcpu, arch.lr));
DEFINE(VCPU_CR, offsetof(struct kvm_vcpu, arch.cr));
diff --git a/arch/powerpc/kvm/44x_tlb.c b/arch/powerpc/kvm/44x_tlb.c
index a207d16..06a5fcf 100644
--- a/arch/powerpc/kvm/44x_tlb.c
+++ b/arch/powerpc/kvm/44x_tlb.c
@@ -125,6 +125,11 @@ static void kvmppc_44x_shadow_release(struct kvm_vcpu *vcpu,
}
}

+void kvmppc_tlbe_set_modified(struct kvm_vcpu *vcpu, unsigned int i)
+{
+ vcpu->arch.shadow_tlb_mod[i] = 1;
+}
+
/* Caller must ensure that the specified guest TLB entry is safe to insert into
* the shadow TLB. */
void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
@@ -172,10 +177,10 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
* use host large pages in the future. */
stlbe->word0 = (gvaddr & PAGE_MASK) | PPC44x_TLB_VALID | PPC44x_TLB_TS
| PPC44x_TLB_4K;
-
stlbe->word1 = (hpaddr & 0xfffffc00) | ((hpaddr >> 32) & 0xf);
stlbe->word2 = kvmppc_44x_tlb_shadow_attrib(flags,
vcpu->arch.msr & MSR_PR);
+ kvmppc_tlbe_set_modified(vcpu, victim);

KVMTRACE_5D(STLB_WRITE, vcpu, victim,
stlbe->tid, stlbe->word0, stlbe->word1, stlbe->word2,
@@ -209,6 +214,7 @@ void kvmppc_mmu_invalidate(struct kvm_vcpu *vcpu, gva_t eaddr,

kvmppc_44x_shadow_release(vcpu, i);
stlbe->word0 = 0;
+ kvmppc_tlbe_set_modified(vcpu, i);
KVMTRACE_5D(STLB_INVAL, vcpu, i,
stlbe->tid, stlbe->word0, stlbe->word1,
stlbe->word2, handler);
@@ -229,6 +235,7 @@ void kvmppc_mmu_priv_switch(struct kvm_vcpu *vcpu, int usermode)

kvmppc_44x_shadow_release(vcpu, i);
stlbe->word0 = 0;
+ kvmppc_tlbe_set_modified(vcpu, i);
KVMTRACE_5D(STLB_INVAL, vcpu, i,
stlbe->tid, stlbe->word0, stlbe->word1,
stlbe->word2, handler);
diff --git a/arch/powerpc/kvm/booke_interrupts.S b/arch/powerpc/kvm/booke_interrupts.S
index 3e88dfa..564ea32 100644
--- a/arch/powerpc/kvm/booke_interrupts.S
+++ b/arch/powerpc/kvm/booke_interrupts.S
@@ -335,7 +335,7 @@ lightweight_exit:
lwz r3, VCPU_PID(r4)
mtspr SPRN_PID, r3

- /* Prevent all TLB updates. */
+ /* Prevent all asynchronous TLB updates. */
mfmsr r5
lis r6, (MSR_EE|MSR_CE|MSR_ME|MSR_DE)@h
ori r6, r6, (MSR_EE|MSR_CE|MSR_ME|MSR_DE)@l
@@ -344,28 +344,45 @@ lightweight_exit:

/* 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 r9, r4, VCPU_SHADOW_TLB - 4
- li r6, 0
+ li r5, PPC44x_TLB_SIZE
+ lis r5, tlb_44x_hwater@ha
+ lwz r5, tlb_44x_hwater@l(r5)
+ mtctr r5
+ addi r9, r4, VCPU_SHADOW_TLB
+ addi r5, r4, VCPU_SHADOW_MOD
+ li r3, 0
1:
+ lbzx r7, r3, r5
+ cmpwi r7, 0
+ beq 3f
+
/* Load guest entry. */
- lwzu r7, 4(r9)
+ mulli r11, r3, TLBE_BYTES
+ add r11, r11, r9
+ lwz r7, 0(r11)
mtspr SPRN_MMUCR, r7
- lwzu r7, 4(r9)
- tlbwe r7, r6, PPC44x_TLB_PAGEID
- lwzu r7, 4(r9)
- tlbwe r7, r6, PPC44x_TLB_XLAT
- lwzu r7, 4(r9)
- tlbwe r7, r6, PPC44x_TLB_ATTRIB
- /* Increment index. */
- addi r6, r6, 1
- cmpw r6, r8
- blt 1b
+ lwz r7, 4(r11)
+ tlbwe r7, r3, PPC44x_TLB_PAGEID
+ lwz r7, 8(r11)
+ tlbwe r7, r3, PPC44x_TLB_XLAT
+ lwz r7, 12(r11)
+ tlbwe r7, r3, PPC44x_TLB_ATTRIB
+3:
+ addi r3, r3, 1 /* Increment index. */
+ bdnz 1b
+
mtspr SPRN_MMUCR, r10 /* Restore host MMUCR. */

+ /* Clear bitmap of modified TLB entries */
+ li r5, PPC44x_TLB_SIZE>>2
+ mtctr r5
+ addi r5, r4, VCPU_SHADOW_MOD - 4
+ li r6, 0
+1:
+ stwu r6, 4(r5)
+ bdnz 1b
+
iccci 0, 0 /* XXX hack */

/* Load some guest volatiles. */
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index b756071..90a6fc4 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -27,6 +27,7 @@
#include <asm/cputable.h>
#include <asm/uaccess.h>
#include <asm/kvm_ppc.h>
+#include <asm/tlbflush.h>


gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
@@ -307,14 +308,28 @@ static void kvmppc_load_guest_debug_registers(struct kvm_vcpu *vcpu)

void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
+ int i;
+
if (vcpu->guest_debug.enabled)
kvmppc_load_guest_debug_registers(vcpu);
+
+ /* Mark every guest entry in the shadow TLB entry modified, so that they
+ * will all be reloaded on the next vcpu run (instead of being
+ * demand-faulted). */
+ for (i = 0; i <= tlb_44x_hwater; i++)
+ kvmppc_tlbe_set_modified(vcpu, i);
}

void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
if (vcpu->guest_debug.enabled)
kvmppc_restore_host_debug_state(vcpu);
+
+ /* Don't leave guest TLB entries resident when being de-scheduled. */
+ /* XXX It would be nice to differentiate between heavyweight exit and
+ * sched_out here, since we could avoid the TLB flush for heavyweight
+ * exits. */
+ _tlbia();
}

int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
--
1.6.0.1


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