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Subject[PATCH 10/11] powerpc/kvm: KVM-HV HPT resizing implementation
Date
This adds the "guts" of the implementation for the HPT resizing PAPR
extension. It has the code to allocate and clear a new HPT, rehash an
existing HPT's entries into it, and accomplish the switchover for a
KVM guest from the old HPT to the new one.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
arch/powerpc/kvm/book3s_64_mmu_hv.c | 188 +++++++++++++++++++++++++++++++++++-
1 file changed, 187 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index a2ac749..2a86c07 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -66,6 +66,10 @@ struct kvm_resize_hpt {
/* These fields protected by kvm->lock */
int error;
bool prepare_done;
+
+ /* Private to the work thread, until prepare_done is true,
+ * then protected by kvm->resize_hpt_sem */
+ struct kvm_hpt_info hpt;
};

static void kvmppc_rmap_reset(struct kvm *kvm);
@@ -1189,21 +1193,203 @@ void kvmppc_unpin_guest_page(struct kvm *kvm, void *va, unsigned long gpa,
*/
static int resize_hpt_allocate(struct kvm_resize_hpt *resize)
{
+ int rc;
+
+ rc = kvmppc_allocate_hpt(&resize->hpt, resize->order);
+ if (rc < 0)
+ return rc;
+
+ resize_hpt_debug(resize, "resize_hpt_allocate(): HPT @ 0x%lx\n",
+ resize->hpt.virt);
+
return 0;
}

+static unsigned long resize_hpt_rehash_hpte(struct kvm_resize_hpt *resize,
+ unsigned long idx)
+{
+ struct kvm *kvm = resize->kvm;
+ struct kvm_hpt_info *old = &kvm->arch.hpt;
+ struct kvm_hpt_info *new = &resize->hpt;
+ unsigned long old_hash_mask = (1ULL << (old->order - 7)) - 1;
+ unsigned long new_hash_mask = (1ULL << (new->order - 7)) - 1;
+ __be64 *hptep, *new_hptep;
+ unsigned long vpte, rpte, guest_rpte;
+ int ret;
+ struct revmap_entry *rev;
+ unsigned long apsize, psize, avpn, pteg, hash;
+ unsigned long new_idx, new_pteg, replace_vpte;
+
+ hptep = (__be64 *)(old->virt + (idx << 4));
+
+ /* Guest is stopped, so new HPTEs can't be added or faulted
+ * in, only unmapped or altered by host actions. So, it's
+ * safe to check this before we take the HPTE lock */
+ vpte = be64_to_cpu(hptep[0]);
+ if (!(vpte & HPTE_V_VALID) && !(vpte & HPTE_V_ABSENT))
+ return 0; /* nothing to do */
+
+ while (!try_lock_hpte(hptep, HPTE_V_HVLOCK))
+ cpu_relax();
+
+ vpte = be64_to_cpu(hptep[0]);
+
+ ret = 0;
+ if (!(vpte & HPTE_V_VALID) && !(vpte & HPTE_V_ABSENT))
+ /* Nothing to do */
+ goto out;
+
+ /* Unmap */
+ rev = &old->rev[idx];
+ guest_rpte = rev->guest_rpte;
+
+ ret = -EIO;
+ apsize = hpte_page_size(vpte, guest_rpte);
+ if (!apsize)
+ goto out;
+
+ if (vpte & HPTE_V_VALID) {
+ unsigned long gfn = hpte_rpn(guest_rpte, apsize);
+ int srcu_idx = srcu_read_lock(&kvm->srcu);
+ struct kvm_memory_slot *memslot =
+ __gfn_to_memslot(kvm_memslots(kvm), gfn);
+
+ if (memslot) {
+ unsigned long *rmapp;
+ rmapp = &memslot->arch.rmap[gfn - memslot->base_gfn];
+
+ lock_rmap(rmapp);
+ kvmppc_unmap_hpte(kvm, idx, rmapp, gfn);
+ unlock_rmap(rmapp);
+ }
+
+ srcu_read_unlock(&kvm->srcu, srcu_idx);
+ }
+
+ /* Reload PTE after unmap */
+ vpte = be64_to_cpu(hptep[0]);
+
+ BUG_ON(vpte & HPTE_V_VALID);
+ BUG_ON(!(vpte & HPTE_V_ABSENT));
+
+ ret = 0;
+ if (!(vpte & HPTE_V_BOLTED))
+ goto out;
+
+ rpte = be64_to_cpu(hptep[1]);
+ psize = hpte_base_page_size(vpte, rpte);
+ avpn = HPTE_V_AVPN_VAL(vpte) & ~((psize - 1) >> 23);
+ pteg = idx / HPTES_PER_GROUP;
+ if (vpte & HPTE_V_SECONDARY)
+ pteg = ~pteg;
+
+ if (!(vpte & HPTE_V_1TB_SEG)) {
+ unsigned long offset, vsid;
+
+ /* We only have 28 - 23 bits of offset in avpn */
+ offset = (avpn & 0x1f) << 23;
+ vsid = avpn >> 5;
+ /* We can find more bits from the pteg value */
+ if (psize < (1ULL << 23))
+ offset |= ((vsid ^ pteg) & old_hash_mask) * psize;
+
+ hash = vsid ^ (offset / psize);
+ } else {
+ unsigned long offset, vsid;
+
+ /* We only have 40 - 23 bits of seg_off in avpn */
+ offset = (avpn & 0x1ffff) << 23;
+ vsid = avpn >> 17;
+ if (psize < (1ULL << 23))
+ offset |= ((vsid ^ (vsid << 25) ^ pteg) & old_hash_mask) * psize;
+
+ hash = vsid ^ (vsid << 25) ^ (offset / psize);
+ }
+
+ new_pteg = hash & new_hash_mask;
+ if (vpte & HPTE_V_SECONDARY) {
+ BUG_ON(~pteg != (hash & old_hash_mask));
+ new_pteg = ~new_pteg;
+ } else {
+ BUG_ON(pteg != (hash & old_hash_mask));
+ }
+
+ new_idx = new_pteg * HPTES_PER_GROUP + (idx % HPTES_PER_GROUP);
+ new_hptep = (__be64 *)(new->virt + (new_idx << 4));
+
+ replace_vpte = be64_to_cpu(new_hptep[0]);
+
+ if (replace_vpte & (HPTE_V_VALID | HPTE_V_ABSENT)) {
+ BUG_ON(new->order >= old->order);
+
+ if (replace_vpte & HPTE_V_BOLTED) {
+ if (vpte & HPTE_V_BOLTED)
+ /* Bolted collision, nothing we can do */
+ ret = -ENOSPC;
+ /* Discard the new HPTE */
+ goto out;
+ }
+
+ /* Discard the previous HPTE */
+ }
+
+ new_hptep[1] = cpu_to_be64(rpte);
+ new->rev[new_idx].guest_rpte = guest_rpte;
+ /* No need for a barrier, since new HPT isn't active */
+ new_hptep[0] = cpu_to_be64(vpte);
+ unlock_hpte(new_hptep, vpte);
+
+out:
+ unlock_hpte(hptep, vpte);
+ return ret;
+}
+
static int resize_hpt_rehash(struct kvm_resize_hpt *resize)
{
- return -EIO;
+ struct kvm *kvm = resize->kvm;
+ unsigned long i;
+ int rc;
+
+ for (i = 0; i < kvmppc_hpt_npte(&kvm->arch.hpt); i++) {
+ rc = resize_hpt_rehash_hpte(resize, i);
+ if (rc != 0)
+ return rc;
+ }
+
+ return 0;
}

static void resize_hpt_pivot(struct kvm_resize_hpt *resize)
{
+ struct kvm *kvm = resize->kvm;
+ struct kvm_hpt_info hpt_tmp;
+
+ /* Exchange the pending tables in the resize structure with
+ * the active tables */
+
+ resize_hpt_debug(resize, "resize_hpt_pivot()\n");
+
+ spin_lock(&kvm->mmu_lock);
+ asm volatile("ptesync" : : : "memory");
+
+ hpt_tmp = kvm->arch.hpt;
+ kvmppc_set_hpt(kvm, &resize->hpt);
+ resize->hpt = hpt_tmp;
+
+ spin_unlock(&kvm->mmu_lock);
+
+ synchronize_srcu_expedited(&kvm->srcu);
+
+ resize_hpt_debug(resize, "resize_hpt_pivot() done\n");
}

static void resize_hpt_release(struct kvm *kvm, struct kvm_resize_hpt *resize)
{
BUG_ON(kvm->arch.resize_hpt != resize);
+
+ if (resize->hpt.virt)
+ kvmppc_free_hpt(&resize->hpt);
+
kvm->arch.resize_hpt = NULL;
kfree(resize);
}
--
2.9.3
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