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, 31 insertions, 26 deletions

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index ce5a13fb974b..6ed0a84ef91c 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -51,8 +51,6 @@
 #include <linux/highmem.h>
 #include <linux/hugetlb.h>
 
-#define LARGE_PAGE_ORDER	24	/* 16MB pages */
-
 /* #define EXIT_DEBUG */
 /* #define EXIT_DEBUG_SIMPLE */
 /* #define EXIT_DEBUG_INT */
@@ -1074,24 +1072,26 @@ long kvm_vm_ioctl_allocate_rma(struct kvm *kvm, struct kvm_allocate_rma *ret)
 	return fd;
 }
 
+static unsigned long slb_pgsize_encoding(unsigned long psize)
+{
+	unsigned long senc = 0;
+
+	if (psize > 0x1000) {
+		senc = SLB_VSID_L;
+		if (psize == 0x10000)
+			senc |= SLB_VSID_LP_01;
+	}
+	return senc;
+}
+
 int kvmppc_core_prepare_memory_region(struct kvm *kvm,
 				struct kvm_userspace_memory_region *mem)
 {
-	unsigned long psize;
 	unsigned long npages;
 	unsigned long *phys;
 
-	/* For now, only allow 16MB-aligned slots */
-	psize = kvm->arch.ram_psize;
-	if ((mem->memory_size & (psize - 1)) ||
-	    (mem->guest_phys_addr & (psize - 1))) {
-		pr_err("bad memory_size=%llx @ %llx\n",
-		       mem->memory_size, mem->guest_phys_addr);
-		return -EINVAL;
-	}
-
 	/* Allocate a slot_phys array */
-	npages = mem->memory_size >> kvm->arch.ram_porder;
+	npages = mem->memory_size >> PAGE_SHIFT;
 	phys = kvm->arch.slot_phys[mem->slot];
 	if (!phys) {
 		phys = vzalloc(npages * sizeof(unsigned long));
@@ -1119,6 +1119,8 @@ static void unpin_slot(struct kvm *kvm, int slot_id)
 				continue;
 			pfn = physp[j] >> PAGE_SHIFT;
 			page = pfn_to_page(pfn);
+			if (PageHuge(page))
+				page = compound_head(page);
 			SetPageDirty(page);
 			put_page(page);
 		}
@@ -1141,12 +1143,12 @@ static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu)
 	unsigned long hva;
 	struct kvm_memory_slot *memslot;
 	struct vm_area_struct *vma;
-	unsigned long lpcr;
+	unsigned long lpcr, senc;
 	unsigned long psize, porder;
 	unsigned long rma_size;
 	unsigned long rmls;
 	unsigned long *physp;
-	unsigned long i, npages, pa;
+	unsigned long i, npages;
 
 	mutex_lock(&kvm->lock);
 	if (kvm->arch.rma_setup_done)
@@ -1168,8 +1170,7 @@ static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu)
 		goto up_out;
 
 	psize = vma_kernel_pagesize(vma);
-	if (psize != kvm->arch.ram_psize)
-		goto up_out;
+	porder = __ilog2(psize);
 
 	/* Is this one of our preallocated RMAs? */
 	if (vma->vm_file && vma->vm_file->f_op == &kvm_rma_fops &&
@@ -1186,13 +1187,20 @@ static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu)
 			goto out;
 		}
 
+		/* We can handle 4k, 64k or 16M pages in the VRMA */
+		err = -EINVAL;
+		if (!(psize == 0x1000 || psize == 0x10000 ||
+		      psize == 0x1000000))
+			goto out;
+
 		/* Update VRMASD field in the LPCR */
-		lpcr = kvm->arch.lpcr & ~(0x1fUL << LPCR_VRMASD_SH);
-		lpcr |= LPCR_VRMA_L;
+		senc = slb_pgsize_encoding(psize);
+		lpcr = kvm->arch.lpcr & ~LPCR_VRMASD;
+		lpcr |= senc << (LPCR_VRMASD_SH - 4);
 		kvm->arch.lpcr = lpcr;
 
 		/* Create HPTEs in the hash page table for the VRMA */
-		kvmppc_map_vrma(vcpu, memslot);
+		kvmppc_map_vrma(vcpu, memslot, porder);
 
 	} else {
 		/* Set up to use an RMO region */
@@ -1231,13 +1239,12 @@ static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu)
 			ri->base_pfn << PAGE_SHIFT, rma_size, lpcr);
 
 		/* Initialize phys addrs of pages in RMO */
-		porder = kvm->arch.ram_porder;
-		npages = rma_size >> porder;
-		pa = ri->base_pfn << PAGE_SHIFT;
+		npages = ri->npages;
+		porder = __ilog2(npages);
 		physp = kvm->arch.slot_phys[memslot->id];
 		spin_lock(&kvm->arch.slot_phys_lock);
 		for (i = 0; i < npages; ++i)
-			physp[i] = pa + (i << porder);
+			physp[i] = ((ri->base_pfn + i) << PAGE_SHIFT) + porder;
 		spin_unlock(&kvm->arch.slot_phys_lock);
 	}
 
@@ -1266,8 +1273,6 @@ int kvmppc_core_init_vm(struct kvm *kvm)
 
 	INIT_LIST_HEAD(&kvm->arch.spapr_tce_tables);
 
-	kvm->arch.ram_psize = 1ul << LARGE_PAGE_ORDER;
-	kvm->arch.ram_porder = LARGE_PAGE_ORDER;
 	kvm->arch.rma = NULL;
 
 	kvm->arch.host_sdr1 = mfspr(SPRN_SDR1);