KVM: PPC: Allow use of small pages to back Book3S HV guests

This relaxes the requirement that the guest memory be provided as
16MB huge pages, allowing it to be provided as normal memory, i.e.
in pages of PAGE_SIZE bytes (4k or 64k).  To allow this, we index
the kvm->arch.slot_phys[] arrays with a small page index, even if
huge pages are being used, and use the low-order 5 bits of each
entry to store the order of the enclosing page with respect to
normal pages, i.e. log_2(enclosing_page_size / PAGE_SIZE).

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, 39 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 87016ccd8648..cc18f3d67a57 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -34,8 +34,6 @@
 #include <asm/ppc-opcode.h>
 #include <asm/cputable.h>
 
-/* Pages in the VRMA are 16MB pages */
-#define VRMA_PAGE_ORDER	24
 #define VRMA_VSID	0x1ffffffUL	/* 1TB VSID reserved for VRMA */
 
 /* POWER7 has 10-bit LPIDs, PPC970 has 6-bit LPIDs */
@@ -95,17 +93,31 @@ void kvmppc_free_hpt(struct kvm *kvm)
 	free_pages(kvm->arch.hpt_virt, HPT_ORDER - PAGE_SHIFT);
 }
 
-void kvmppc_map_vrma(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot)
+/* Bits in first HPTE dword for pagesize 4k, 64k or 16M */
+static inline unsigned long hpte0_pgsize_encoding(unsigned long pgsize)
+{
+	return (pgsize > 0x1000) ? HPTE_V_LARGE : 0;
+}
+
+/* Bits in second HPTE dword for pagesize 4k, 64k or 16M */
+static inline unsigned long hpte1_pgsize_encoding(unsigned long pgsize)
+{
+	return (pgsize == 0x10000) ? 0x1000 : 0;
+}
+
+void kvmppc_map_vrma(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
+		     unsigned long porder)
 {
-	struct kvm *kvm = vcpu->kvm;
 	unsigned long i;
 	unsigned long npages;
 	unsigned long hp_v, hp_r;
 	unsigned long addr, hash;
-	unsigned long porder = kvm->arch.ram_porder;
+	unsigned long psize;
+	unsigned long hp0, hp1;
 	long ret;
 
-	npages = kvm->arch.slot_npages[memslot->id];
+	psize = 1ul << porder;
+	npages = memslot->npages >> (porder - PAGE_SHIFT);
 
 	/* VRMA can't be > 1TB */
 	if (npages > 1ul << (40 - porder))
@@ -114,6 +126,11 @@ void kvmppc_map_vrma(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot)
 	if (npages > HPT_NPTEG)
 		npages = HPT_NPTEG;
 
+	hp0 = HPTE_V_1TB_SEG | (VRMA_VSID << (40 - 16)) |
+		HPTE_V_BOLTED | hpte0_pgsize_encoding(psize);
+	hp1 = hpte1_pgsize_encoding(psize) |
+		HPTE_R_R | HPTE_R_C | HPTE_R_M | PP_RWXX;
+
 	for (i = 0; i < npages; ++i) {
 		addr = i << porder;
 		/* can't use hpt_hash since va > 64 bits */
@@ -125,10 +142,8 @@ void kvmppc_map_vrma(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot)
 		 * is available and use it.
 		 */
 		hash = (hash << 3) + 7;
-		hp_v = HPTE_V_1TB_SEG | (VRMA_VSID << (40 - 16)) |
-			(i << (VRMA_PAGE_ORDER - 16)) | HPTE_V_BOLTED |
-			HPTE_V_LARGE | HPTE_V_VALID;
-		hp_r = addr | HPTE_R_R | HPTE_R_C | HPTE_R_M | PP_RWXX;
+		hp_v = hp0 | ((addr >> 16) & ~0x7fUL);
+		hp_r = hp1 | addr;
 		ret = kvmppc_virtmode_h_enter(vcpu, H_EXACT, hash, hp_v, hp_r);
 		if (ret != H_SUCCESS) {
 			pr_err("KVM: map_vrma at %lx failed, ret=%ld\n",
@@ -176,22 +191,25 @@ static void kvmppc_mmu_book3s_64_hv_reset_msr(struct kvm_vcpu *vcpu)
  * one already in the kvm->arch.slot_phys[][] arrays.
  */
 static long kvmppc_get_guest_page(struct kvm *kvm, unsigned long gfn,
-				  struct kvm_memory_slot *memslot)
+				  struct kvm_memory_slot *memslot,
+				  unsigned long psize)
 {
 	unsigned long start;
-	long np;
-	struct page *page, *pages[1];
+	long np, err;
+	struct page *page, *hpage, *pages[1];
+	unsigned long s, pgsize;
 	unsigned long *physp;
-	unsigned long pfn, i;
+	unsigned int got, pgorder;
+	unsigned long pfn, i, npages;
 
 	physp = kvm->arch.slot_phys[memslot->id];
 	if (!physp)
 		return -EINVAL;
-	i = (gfn - memslot->base_gfn) >> (kvm->arch.ram_porder - PAGE_SHIFT);
-	if (physp[i])
+	if (physp[gfn - memslot->base_gfn])
 		return 0;
 
 	page = NULL;
+	pgsize = psize;
 	start = gfn_to_hva_memslot(memslot, gfn);
 
 	/* Instantiate and get the page we want access to */
@@ -199,25 +217,46 @@ static long kvmppc_get_guest_page(struct kvm *kvm, unsigned long gfn,
 	if (np != 1)
 		return -EINVAL;
 	page = pages[0];
-
-	/* Check it's a 16MB page */
-	if (!PageHead(page) ||
-	    compound_order(page) != (kvm->arch.ram_porder - PAGE_SHIFT)) {
-		pr_err("page at %lx isn't 16MB (o=%d)\n",
-		       start, compound_order(page));
-		put_page(page);
-		return -EINVAL;
+	got = KVMPPC_GOT_PAGE;
+
+	/* See if this is a large page */
+	s = PAGE_SIZE;
+	if (PageHuge(page)) {
+		hpage = compound_head(page);
+		s <<= compound_order(hpage);
+		/* Get the whole large page if slot alignment is ok */
+		if (s > psize && slot_is_aligned(memslot, s) &&
+		    !(memslot->userspace_addr & (s - 1))) {
+			start &= ~(s - 1);
+			pgsize = s;
+			page = hpage;
+		}
 	}
+	err = -EINVAL;
+	if (s < psize)
+		goto out;
 	pfn = page_to_pfn(page);
 
+	npages = pgsize >> PAGE_SHIFT;
+	pgorder = __ilog2(npages);
+	physp += (gfn - memslot->base_gfn) & ~(npages - 1);
 	spin_lock(&kvm->arch.slot_phys_lock);
-	if (!physp[i])
-		physp[i] = (pfn << PAGE_SHIFT) | KVMPPC_GOT_PAGE;
-	else
-		put_page(page);
+	for (i = 0; i < npages; ++i) {
+		if (!physp[i]) {
+			physp[i] = ((pfn + i) << PAGE_SHIFT) + got + pgorder;
+			got = 0;
+		}
+	}
 	spin_unlock(&kvm->arch.slot_phys_lock);
+	err = 0;
 
-	return 0;
+ out:
+	if (got) {
+		if (PageHuge(page))
+			page = compound_head(page);
+		put_page(page);
+	}
+	return err;
 }
 
 /*
@@ -242,7 +281,9 @@ long kvmppc_virtmode_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 	memslot = gfn_to_memslot(kvm, gfn);
 	if (!memslot || (memslot->flags & KVM_MEMSLOT_INVALID))
 		return H_PARAMETER;
-	if (kvmppc_get_guest_page(kvm, gfn, memslot) < 0)
+	if (!slot_is_aligned(memslot, psize))
+		return H_PARAMETER;
+	if (kvmppc_get_guest_page(kvm, gfn, memslot, psize) < 0)
 		return H_PARAMETER;
 
 	preempt_disable();
@@ -269,8 +310,8 @@ void *kvmppc_pin_guest_page(struct kvm *kvm, unsigned long gpa,
 	struct kvm_memory_slot *memslot;
 	unsigned long gfn = gpa >> PAGE_SHIFT;
 	struct page *page;
-	unsigned long offset;
-	unsigned long pfn, pa;
+	unsigned long psize, offset;
+	unsigned long pa;
 	unsigned long *physp;
 
 	memslot = gfn_to_memslot(kvm, gfn);
@@ -279,20 +320,23 @@ void *kvmppc_pin_guest_page(struct kvm *kvm, unsigned long gpa,
 	physp = kvm->arch.slot_phys[memslot->id];
 	if (!physp)
 		return NULL;
-	physp += (gfn - memslot->base_gfn) >>
-		(kvm->arch.ram_porder - PAGE_SHIFT);
+	physp += gfn - memslot->base_gfn;
 	pa = *physp;
 	if (!pa) {
-		if (kvmppc_get_guest_page(kvm, gfn, memslot) < 0)
+		if (kvmppc_get_guest_page(kvm, gfn, memslot, PAGE_SIZE) < 0)
 			return NULL;
 		pa = *physp;
 	}
-	pfn = pa >> PAGE_SHIFT;
-	page = pfn_to_page(pfn);
+	page = pfn_to_page(pa >> PAGE_SHIFT);
+	psize = PAGE_SIZE;
+	if (PageHuge(page)) {
+		page = compound_head(page);
+		psize <<= compound_order(page);
+	}
 	get_page(page);
-	offset = gpa & (kvm->arch.ram_psize - 1);
+	offset = gpa & (psize - 1);
 	if (nb_ret)
-		*nb_ret = kvm->arch.ram_psize - offset;
+		*nb_ret = psize - offset;
 	return page_address(page) + offset;
 }