[PATCH 43/52] KVM: PPC: Book3s HV: Maintain separate guest and host views of R and C bits

Alexander Graf
2012-01-13T14:31:46Z

From: Paul Mackerras <paulus@samba.org>

This allows both the guest and the host to use the referenced (R) and
changed (C) bits in the guest hashed page table. The guest has a view
of R and C that is maintained in the guest_rpte field of the revmap
entry for the HPTE, and the host has a view that is maintained in the
rmap entry for the associated gfn.

Both view are updated from the guest HPT. If a bit (R or C) is zero
in either view, it will be initially set to zero in the HPTE (or HPTEs),
until set to 1 by hardware. When an HPTE is removed for any reason,
the R and C bits from the HPTE are ORed into both views. We have to
be careful to read the R and C bits from the HPTE after invalidating
it, but before unlocking it, in case of any late updates by the hardware.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
arch/powerpc/include/asm/kvm_host.h | 5 ++-
arch/powerpc/kvm/book3s_64_mmu_hv.c | 48 +++++++++++++++++++++-------------
arch/powerpc/kvm/book3s_hv_rm_mmu.c | 45 +++++++++++++++++++--------------
3 files changed, 59 insertions(+), 39 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 968f3aa..1cb6e52 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -200,8 +200,9 @@ struct revmap_entry {
* index in the guest HPT of a HPTE that points to the page.
*/
#define KVMPPC_RMAP_LOCK_BIT 63
-#define KVMPPC_RMAP_REF_BIT 33
-#define KVMPPC_RMAP_REFERENCED (1ul << KVMPPC_RMAP_REF_BIT)
+#define KVMPPC_RMAP_RC_SHIFT 32
+#define KVMPPC_RMAP_REFERENCED (HPTE_R_R << KVMPPC_RMAP_RC_SHIFT)
+#define KVMPPC_RMAP_CHANGED (HPTE_R_C << KVMPPC_RMAP_RC_SHIFT)
#define KVMPPC_RMAP_PRESENT 0x100000000ul
#define KVMPPC_RMAP_INDEX 0xfffffffful

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 66d6452..aa51dde 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -505,6 +505,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
unsigned long is_io;
unsigned int writing, write_ok;
struct vm_area_struct *vma;
+ unsigned long rcbits;

/*
* Real-mode code has already searched the HPT and found the
@@ -640,11 +641,17 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
goto out_unlock;
}

+ /* Only set R/C in real HPTE if set in both *rmap and guest_rpte */
+ rcbits = *rmap >> KVMPPC_RMAP_RC_SHIFT;
+ r &= rcbits | ~(HPTE_R_R | HPTE_R_C);
+
if (hptep[0] & HPTE_V_VALID) {
/* HPTE was previously valid, so we need to invalidate it */
unlock_rmap(rmap);
hptep[0] |= HPTE_V_ABSENT;
kvmppc_invalidate_hpte(kvm, hptep, index);
+ /* don't lose previous R and C bits */
+ r |= hptep[1] & (HPTE_R_R | HPTE_R_C);
} else {
kvmppc_add_revmap_chain(kvm, rev, rmap, index, 0);
}
@@ -701,50 +708,55 @@ static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp,
struct revmap_entry *rev = kvm->arch.revmap;
unsigned long h, i, j;
unsigned long *hptep;
- unsigned long ptel, psize;
+ unsigned long ptel, psize, rcbits;

for (;;) {
- while (test_and_set_bit_lock(KVMPPC_RMAP_LOCK_BIT, rmapp))
- cpu_relax();
+ lock_rmap(rmapp);
if (!(*rmapp & KVMPPC_RMAP_PRESENT)) {
- __clear_bit_unlock(KVMPPC_RMAP_LOCK_BIT, rmapp);
+ unlock_rmap(rmapp);
break;
}

/*
* To avoid an ABBA deadlock with the HPTE lock bit,
- * we have to unlock the rmap chain before locking the HPTE.
- * Thus we remove the first entry, unlock the rmap chain,
- * lock the HPTE and then check that it is for the
- * page we're unmapping before changing it to non-present.
+ * we can't spin on the HPTE lock while holding the
+ * rmap chain lock.
*/
i = *rmapp & KVMPPC_RMAP_INDEX;
+ hptep = (unsigned long *) (kvm->arch.hpt_virt + (i << 4));
+ 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();
+ continue;
+ }
j = rev[i].forw;
if (j == i) {
/* chain is now empty */
- j = 0;
+ *rmapp &= ~(KVMPPC_RMAP_PRESENT | KVMPPC_RMAP_INDEX);
} else {
/* remove i from chain */
h = rev[i].back;
rev[h].forw = j;
rev[j].back = h;
rev[i].forw = rev[i].back = i;
- j |= KVMPPC_RMAP_PRESENT;
+ *rmapp = (*rmapp & ~KVMPPC_RMAP_INDEX) | j;
}
- smp_wmb();
- *rmapp = j | (1ul << KVMPPC_RMAP_REF_BIT);

- /* Now lock, check and modify the HPTE */
- hptep = (unsigned long *) (kvm->arch.hpt_virt + (i << 4));
- while (!try_lock_hpte(hptep, HPTE_V_HVLOCK))
- cpu_relax();
+ /* Now check and modify the HPTE */
ptel = rev[i].guest_rpte;
psize = hpte_page_size(hptep[0], ptel);
if ((hptep[0] & HPTE_V_VALID) &&
hpte_rpn(ptel, psize) == gfn) {
- kvmppc_invalidate_hpte(kvm, hptep, i);
hptep[0] |= HPTE_V_ABSENT;
+ kvmppc_invalidate_hpte(kvm, hptep, i);
+ /* Harvest R and C */
+ rcbits = hptep[1] & (HPTE_R_R | HPTE_R_C);
+ *rmapp |= rcbits << KVMPPC_RMAP_RC_SHIFT;
+ rev[i].guest_rpte = ptel | rcbits;
}
+ unlock_rmap(rmapp);
hptep[0] &= ~HPTE_V_HVLOCK;
}
return 0;
@@ -767,7 +779,7 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
kvm_unmap_rmapp(kvm, rmapp, gfn);
while (test_and_set_bit_lock(KVMPPC_RMAP_LOCK_BIT, rmapp))
cpu_relax();
- __clear_bit(KVMPPC_RMAP_REF_BIT, rmapp);
+ *rmapp &= ~KVMPPC_RMAP_REFERENCED;
__clear_bit_unlock(KVMPPC_RMAP_LOCK_BIT, rmapp);
return 1;
}
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index ba4a137..91b45a0 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -87,15 +87,17 @@ EXPORT_SYMBOL_GPL(kvmppc_add_revmap_chain);

/* Remove this HPTE from the chain for a real page */
static void remove_revmap_chain(struct kvm *kvm, long pte_index,
- unsigned long hpte_v)
+ struct revmap_entry *rev,
+ unsigned long hpte_v, unsigned long hpte_r)
{
- struct revmap_entry *rev, *next, *prev;
+ struct revmap_entry *next, *prev;
unsigned long gfn, ptel, head;
struct kvm_memory_slot *memslot;
unsigned long *rmap;
+ unsigned long rcbits;

- rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
- ptel = rev->guest_rpte;
+ rcbits = hpte_r & (HPTE_R_R | HPTE_R_C);
+ ptel = rev->guest_rpte |= rcbits;
gfn = hpte_rpn(ptel, hpte_page_size(hpte_v, ptel));
memslot = builtin_gfn_to_memslot(kvm, gfn);
if (!memslot || (memslot->flags & KVM_MEMSLOT_INVALID))
@@ -116,6 +118,7 @@ static void remove_revmap_chain(struct kvm *kvm, long pte_index,
else
*rmap = (*rmap & ~KVMPPC_RMAP_INDEX) | head;
}
+ *rmap |= rcbits << KVMPPC_RMAP_RC_SHIFT;
unlock_rmap(rmap);
}

@@ -162,6 +165,7 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
pte_t pte;
unsigned int writing;
unsigned long mmu_seq;
+ unsigned long rcbits;
bool realmode = vcpu->arch.vcore->vcore_state == VCORE_RUNNING;

psize = hpte_page_size(pteh, ptel);
@@ -320,6 +324,9 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
} else {
kvmppc_add_revmap_chain(kvm, rev, rmap, pte_index,
realmode);
+ /* Only set R/C in real HPTE if already set in *rmap */
+ rcbits = *rmap >> KVMPPC_RMAP_RC_SHIFT;
+ ptel &= rcbits | ~(HPTE_R_R | HPTE_R_C);
}
}

@@ -394,7 +401,8 @@ long kvmppc_h_remove(struct kvm_vcpu *vcpu, unsigned long flags,
asm volatile("tlbiel %0" : : "r" (rb));
asm volatile("ptesync" : : : "memory");
}
- remove_revmap_chain(kvm, pte_index, v);
+ /* Read PTE low word after tlbie to get final R/C values */
+ remove_revmap_chain(kvm, pte_index, rev, v, hpte[1]);
}
r = rev->guest_rpte;
unlock_hpte(hpte, 0);
@@ -469,12 +477,13 @@ long kvmppc_h_bulk_remove(struct kvm_vcpu *vcpu)

args[j] = ((0x80 | flags) << 56) + pte_index;
rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
- /* insert R and C bits from guest PTE */
- rcbits = rev->guest_rpte & (HPTE_R_R|HPTE_R_C);
- args[j] |= rcbits << (56 - 5);

- if (!(hp[0] & HPTE_V_VALID))
+ if (!(hp[0] & HPTE_V_VALID)) {
+ /* insert R and C bits from PTE */
+ rcbits = rev->guest_rpte & (HPTE_R_R|HPTE_R_C);
+ args[j] |= rcbits << (56 - 5);
continue;
+ }

hp[0] &= ~HPTE_V_VALID; /* leave it locked */
tlbrb[n] = compute_tlbie_rb(hp[0], hp[1], pte_index);
@@ -505,13 +514,16 @@ long kvmppc_h_bulk_remove(struct kvm_vcpu *vcpu)
asm volatile("ptesync" : : : "memory");
}

+ /* Read PTE low words after tlbie to get final R/C values */
for (k = 0; k < n; ++k) {
j = indexes[k];
pte_index = args[j] & ((1ul << 56) - 1);
hp = hptes[k];
rev = revs[k];
- remove_revmap_chain(kvm, pte_index, hp[0]);
- unlock_hpte(hp, 0);
+ remove_revmap_chain(kvm, pte_index, rev, hp[0], hp[1]);
+ rcbits = rev->guest_rpte & (HPTE_R_R|HPTE_R_C);
+ args[j] |= rcbits << (56 - 5);
+ hp[0] = 0;
}
}

@@ -595,8 +607,7 @@ long kvmppc_h_read(struct kvm_vcpu *vcpu, unsigned long flags,
pte_index &= ~3;
n = 4;
}
- if (flags & H_R_XLATE)
- rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
+ rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
for (i = 0; i < n; ++i, ++pte_index) {
hpte = (unsigned long *)(kvm->arch.hpt_virt + (pte_index << 4));
v = hpte[0] & ~HPTE_V_HVLOCK;
@@ -605,12 +616,8 @@ long kvmppc_h_read(struct kvm_vcpu *vcpu, unsigned long flags,
v &= ~HPTE_V_ABSENT;
v |= HPTE_V_VALID;
}
- if (v & HPTE_V_VALID) {
- if (rev)
- r = rev[i].guest_rpte;
- else
- r = hpte[1] | HPTE_R_RPN;
- }
+ if (v & HPTE_V_VALID)
+ r = rev[i].guest_rpte | (r & (HPTE_R_R | HPTE_R_C));
vcpu->arch.gpr[4 + i * 2] = v;
vcpu->arch.gpr[5 + i * 2] = r;
}
--
1.6.0.2