[PATCH 44/52] KVM: PPC: Book3S HV: Use the hardware referenced bit for kvm_age_hva

Alexander Graf
2012-01-13T14:31:47Z

From: Paul Mackerras <paulus@samba.org>

This uses the host view of the hardware R (referenced) bit to speed
up kvm_age_hva() and kvm_test_age_hva(). Instead of removing all
the relevant HPTEs in kvm_age_hva(), we now just reset their R bits
if set. Also, kvm_test_age_hva() now scans the relevant HPTEs to
see if any of them have R set.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
arch/powerpc/include/asm/kvm_book3s.h | 2 +
arch/powerpc/kvm/book3s_64_mmu_hv.c | 81 ++++++++++++++++++++++++++++-----
arch/powerpc/kvm/book3s_hv_rm_mmu.c | 19 ++++++++
3 files changed, 91 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index 9240ceb..33fdc09 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -147,6 +147,8 @@ extern void kvmppc_add_revmap_chain(struct kvm *kvm, struct revmap_entry *rev,
unsigned long *rmap, long pte_index, int realmode);
extern void kvmppc_invalidate_hpte(struct kvm *kvm, unsigned long *hptep,
unsigned long pte_index);
+void kvmppc_clear_ref_hpte(struct kvm *kvm, unsigned long *hptep,
+ unsigned long pte_index);
extern void *kvmppc_pin_guest_page(struct kvm *kvm, unsigned long addr,
unsigned long *nb_ret);
extern void kvmppc_unpin_guest_page(struct kvm *kvm, void *addr);
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index aa51dde..926e2b9 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -772,16 +772,50 @@ int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long gfn)
{
- if (!kvm->arch.using_mmu_notifiers)
- return 0;
- if (!(*rmapp & KVMPPC_RMAP_REFERENCED))
- return 0;
- kvm_unmap_rmapp(kvm, rmapp, gfn);
- while (test_and_set_bit_lock(KVMPPC_RMAP_LOCK_BIT, rmapp))
- cpu_relax();
- *rmapp &= ~KVMPPC_RMAP_REFERENCED;
- __clear_bit_unlock(KVMPPC_RMAP_LOCK_BIT, rmapp);
- return 1;
+ struct revmap_entry *rev = kvm->arch.revmap;
+ unsigned long head, i, j;
+ unsigned long *hptep;
+ int ret = 0;
+
+ retry:
+ lock_rmap(rmapp);
+ if (*rmapp & KVMPPC_RMAP_REFERENCED) {
+ *rmapp &= ~KVMPPC_RMAP_REFERENCED;
+ ret = 1;
+ }
+ if (!(*rmapp & KVMPPC_RMAP_PRESENT)) {
+ unlock_rmap(rmapp);
+ return ret;
+ }
+
+ i = head = *rmapp & KVMPPC_RMAP_INDEX;
+ do {
+ hptep = (unsigned long *) (kvm->arch.hpt_virt + (i << 4));
+ j = rev[i].forw;
+
+ /* If this HPTE isn't referenced, ignore it */
+ if (!(hptep[1] & HPTE_R_R))
+ continue;
+
+ if (!try_lock_hpte(hptep, HPTE_V_HVLOCK)) {
+ /* unlock rmap before spinning on the HPTE lock */
+ unlock_rmap(rmapp);
+ while (hptep[0] & HPTE_V_HVLOCK)
+ cpu_relax();
+ goto retry;
+ }
+
+ /* Now check and modify the HPTE */
+ if ((hptep[0] & HPTE_V_VALID) && (hptep[1] & HPTE_R_R)) {
+ kvmppc_clear_ref_hpte(kvm, hptep, i);
+ rev[i].guest_rpte |= HPTE_R_R;
+ ret = 1;
+ }
+ hptep[0] &= ~HPTE_V_HVLOCK;
+ } while ((i = j) != head);
+
+ unlock_rmap(rmapp);
+ return ret;
}

int kvm_age_hva(struct kvm *kvm, unsigned long hva)
@@ -794,7 +828,32 @@ int kvm_age_hva(struct kvm *kvm, unsigned long hva)
static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long gfn)
{
- return !!(*rmapp & KVMPPC_RMAP_REFERENCED);
+ struct revmap_entry *rev = kvm->arch.revmap;
+ unsigned long head, i, j;
+ unsigned long *hp;
+ int ret = 1;
+
+ if (*rmapp & KVMPPC_RMAP_REFERENCED)
+ return 1;
+
+ lock_rmap(rmapp);
+ if (*rmapp & KVMPPC_RMAP_REFERENCED)
+ goto out;
+
+ if (*rmapp & KVMPPC_RMAP_PRESENT) {
+ i = head = *rmapp & KVMPPC_RMAP_INDEX;
+ do {
+ hp = (unsigned long *)(kvm->arch.hpt_virt + (i << 4));
+ j = rev[i].forw;
+ if (hp[1] & HPTE_R_R)
+ goto out;
+ } while ((i = j) != head);
+ }
+ ret = 0;
+
+ out:
+ unlock_rmap(rmapp);
+ return ret;
}

int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index 91b45a0..5f3c60b 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -641,6 +641,25 @@ void kvmppc_invalidate_hpte(struct kvm *kvm, unsigned long *hptep,
}
EXPORT_SYMBOL_GPL(kvmppc_invalidate_hpte);

+void kvmppc_clear_ref_hpte(struct kvm *kvm, unsigned long *hptep,
+ unsigned long pte_index)
+{
+ unsigned long rb;
+ unsigned char rbyte;
+
+ rb = compute_tlbie_rb(hptep[0], hptep[1], pte_index);
+ rbyte = (hptep[1] & ~HPTE_R_R) >> 8;
+ /* modify only the second-last byte, which contains the ref bit */
+ *((char *)hptep + 14) = rbyte;
+ while (!try_lock_tlbie(&kvm->arch.tlbie_lock))
+ cpu_relax();
+ asm volatile(PPC_TLBIE(%1,%0)"; eieio; tlbsync"
+ : : "r" (rb), "r" (kvm->arch.lpid));
+ asm volatile("ptesync" : : : "memory");
+ kvm->arch.tlbie_lock = 0;
+}
+EXPORT_SYMBOL_GPL(kvmppc_clear_ref_hpte);
+
static int slb_base_page_shift[4] = {
24, /* 16M */
16, /* 64k */
--
1.6.0.2