KVM: PPC: Maintain a doubly-linked list of guest HPTEs for each gfn

This expands the reverse mapping array to contain two links for each
HPTE which are used to link together HPTEs that correspond to the
same guest logical page.  Each circular list of HPTEs is pointed to
by the rmap array entry for the guest logical page, pointed to by
the relevant memslot.  Links are 32-bit HPT entry indexes rather than
full 64-bit pointers, to save space.  We use 3 of the remaining 32
bits in the rmap array entries as a lock bit, a referenced bit and
a present bit (the present bit is needed since HPTE index 0 is valid).
The bit lock for the rmap chain nests inside the HPTE lock bit.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 83 insertions, 1 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index 3f5b016490d..5b31caa4b31 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -54,6 +54,70 @@ static void *real_vmalloc_addr(void *x)
 	return __va(addr);
 }
 
+/*
+ * Add this HPTE into the chain for the real page.
+ * Must be called with the chain locked; it unlocks the chain.
+ */
+static void kvmppc_add_revmap_chain(struct kvm *kvm, struct revmap_entry *rev,
+			     unsigned long *rmap, long pte_index, int realmode)
+{
+	struct revmap_entry *head, *tail;
+	unsigned long i;
+
+	if (*rmap & KVMPPC_RMAP_PRESENT) {
+		i = *rmap & KVMPPC_RMAP_INDEX;
+		head = &kvm->arch.revmap[i];
+		if (realmode)
+			head = real_vmalloc_addr(head);
+		tail = &kvm->arch.revmap[head->back];
+		if (realmode)
+			tail = real_vmalloc_addr(tail);
+		rev->forw = i;
+		rev->back = head->back;
+		tail->forw = pte_index;
+		head->back = pte_index;
+	} else {
+		rev->forw = rev->back = pte_index;
+		i = pte_index;
+	}
+	smp_wmb();
+	*rmap = i | KVMPPC_RMAP_REFERENCED | KVMPPC_RMAP_PRESENT; /* unlock */
+}
+
+/* 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, *next, *prev;
+	unsigned long gfn, ptel, head;
+	struct kvm_memory_slot *memslot;
+	unsigned long *rmap;
+
+	rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
+	ptel = rev->guest_rpte;
+	gfn = hpte_rpn(ptel, hpte_page_size(hpte_v, ptel));
+	memslot = builtin_gfn_to_memslot(kvm, gfn);
+	if (!memslot || (memslot->flags & KVM_MEMSLOT_INVALID))
+		return;
+
+	rmap = real_vmalloc_addr(&memslot->rmap[gfn - memslot->base_gfn]);
+	lock_rmap(rmap);
+
+	head = *rmap & KVMPPC_RMAP_INDEX;
+	next = real_vmalloc_addr(&kvm->arch.revmap[rev->forw]);
+	prev = real_vmalloc_addr(&kvm->arch.revmap[rev->back]);
+	next->back = rev->back;
+	prev->forw = rev->forw;
+	if (head == pte_index) {
+		head = rev->forw;
+		if (head == pte_index)
+			*rmap &= ~(KVMPPC_RMAP_PRESENT | KVMPPC_RMAP_INDEX);
+		else
+			*rmap = (*rmap & ~KVMPPC_RMAP_INDEX) | head;
+	}
+	unlock_rmap(rmap);
+}
+
 long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 		    long pte_index, unsigned long pteh, unsigned long ptel)
 {
@@ -66,6 +130,7 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 	struct kvm_memory_slot *memslot;
 	unsigned long *physp, pte_size;
 	unsigned long is_io;
+	unsigned long *rmap;
 	bool realmode = vcpu->arch.vcore->vcore_state == VCORE_RUNNING;
 
 	psize = hpte_page_size(pteh, ptel);
@@ -83,6 +148,7 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 	if (!slot_is_aligned(memslot, psize))
 		return H_PARAMETER;
 	slot_fn = gfn - memslot->base_gfn;
+	rmap = &memslot->rmap[slot_fn];
 
 	physp = kvm->arch.slot_phys[memslot->id];
 	if (!physp)
@@ -164,13 +230,25 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 	}
 
 	/* Save away the guest's idea of the second HPTE dword */
-	rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
+	rev = &kvm->arch.revmap[pte_index];
+	if (realmode)
+		rev = real_vmalloc_addr(rev);
 	if (rev)
 		rev->guest_rpte = g_ptel;
+
+	/* Link HPTE into reverse-map chain */
+	if (realmode)
+		rmap = real_vmalloc_addr(rmap);
+	lock_rmap(rmap);
+	kvmppc_add_revmap_chain(kvm, rev, rmap, pte_index, realmode);
+
 	hpte[1] = ptel;
+
+	/* Write the first HPTE dword, unlocking the HPTE and making it valid */
 	eieio();
 	hpte[0] = pteh;
 	asm volatile("ptesync" : : : "memory");
+
 	vcpu->arch.gpr[4] = pte_index;
 	return H_SUCCESS;
 }
@@ -220,6 +298,8 @@ long kvmppc_h_remove(struct kvm_vcpu *vcpu, unsigned long flags,
 	vcpu->arch.gpr[4] = v = hpte[0] & ~HPTE_V_HVLOCK;
 	vcpu->arch.gpr[5] = r = hpte[1];
 	rb = compute_tlbie_rb(v, r, pte_index);
+	remove_revmap_chain(kvm, pte_index, v);
+	smp_wmb();
 	hpte[0] = 0;
 	if (!(flags & H_LOCAL)) {
 		while(!try_lock_tlbie(&kvm->arch.tlbie_lock))
@@ -293,6 +373,8 @@ long kvmppc_h_bulk_remove(struct kvm_vcpu *vcpu)
 		flags |= (hp[1] >> 5) & 0x0c;
 		args[i * 2] = ((0x80 | flags) << 56) + pte_index;
 		tlbrb[n_inval++] = compute_tlbie_rb(hp[0], hp[1], pte_index);
+		remove_revmap_chain(kvm, pte_index, hp[0]);
+		smp_wmb();
 		hp[0] = 0;
 	}
 	if (n_inval == 0)