KVM: MIPS/MMU: Convert guest physical map to page table

Current guest physical memory is mapped to host physical addresses using
a single linear array (guest_pmap of length guest_pmap_npages). This was
only really meant to be temporary, and isn't sparse, so its wasteful of
memory. A small amount of RAM at GPA 0 and a small boot exception vector
at GPA 0x1fc00000 cannot be represented without a full 128KiB guest_pmap
allocation (MIPS32 with 16KiB pages), which is one reason why QEMU
currently runs its boot code at the top of RAM instead of the usual boot
exception vector address.

Instead use the existing infrastructure for host virtual page table
management to allocate a page table for guest physical memory too. This
should be sufficient for now, assuming the size of physical memory
doesn't exceed the size of virtual memory. It may need extending in
future to handle XPA (eXtended Physical Addressing) in 32-bit guests, as
supported by VZ guests on P5600.

Some of this code is based loosely on Cavium's VZ KVM implementation.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org

1 files changed, 14 insertions, 34 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index b8f04070bf39..9b72e2c55a0c 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -22,6 +22,7 @@
 #include <asm/page.h>
 #include <asm/cacheflush.h>
 #include <asm/mmu_context.h>
+#include <asm/pgalloc.h>
 #include <asm/pgtable.h>
 
 #include <linux/kvm_host.h>
@@ -94,6 +95,11 @@ void kvm_arch_check_processor_compat(void *rtn)
 
 int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
+	/* Allocate page table to map GPA -> RPA */
+	kvm->arch.gpa_mm.pgd = kvm_pgd_alloc();
+	if (!kvm->arch.gpa_mm.pgd)
+		return -ENOMEM;
+
 	return 0;
 }
 
@@ -112,13 +118,6 @@ void kvm_mips_free_vcpus(struct kvm *kvm)
 	unsigned int i;
 	struct kvm_vcpu *vcpu;
 
-	/* Put the pages we reserved for the guest pmap */
-	for (i = 0; i < kvm->arch.guest_pmap_npages; i++) {
-		if (kvm->arch.guest_pmap[i] != KVM_INVALID_PAGE)
-			kvm_release_pfn_clean(kvm->arch.guest_pmap[i]);
-	}
-	kfree(kvm->arch.guest_pmap);
-
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		kvm_arch_vcpu_free(vcpu);
 	}
@@ -133,9 +132,17 @@ void kvm_mips_free_vcpus(struct kvm *kvm)
 	mutex_unlock(&kvm->lock);
 }
 
+static void kvm_mips_free_gpa_pt(struct kvm *kvm)
+{
+	/* It should always be safe to remove after flushing the whole range */
+	WARN_ON(!kvm_mips_flush_gpa_pt(kvm, 0, ~0));
+	pgd_free(NULL, kvm->arch.gpa_mm.pgd);
+}
+
 void kvm_arch_destroy_vm(struct kvm *kvm)
 {
 	kvm_mips_free_vcpus(kvm);
+	kvm_mips_free_gpa_pt(kvm);
 }
 
 long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl,
@@ -164,36 +171,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
 				   const struct kvm_memory_slot *new,
 				   enum kvm_mr_change change)
 {
-	unsigned long npages = 0;
-	int i;
-
 	kvm_debug("%s: kvm: %p slot: %d, GPA: %llx, size: %llx, QVA: %llx\n",
 		  __func__, kvm, mem->slot, mem->guest_phys_addr,
 		  mem->memory_size, mem->userspace_addr);
-
-	/* Setup Guest PMAP table */
-	if (!kvm->arch.guest_pmap) {
-		if (mem->slot == 0)
-			npages = mem->memory_size >> PAGE_SHIFT;
-
-		if (npages) {
-			kvm->arch.guest_pmap_npages = npages;
-			kvm->arch.guest_pmap =
-			    kzalloc(npages * sizeof(unsigned long), GFP_KERNEL);
-
-			if (!kvm->arch.guest_pmap) {
-				kvm_err("Failed to allocate guest PMAP\n");
-				return;
-			}
-
-			kvm_debug("Allocated space for Guest PMAP Table (%ld pages) @ %p\n",
-				  npages, kvm->arch.guest_pmap);
-
-			/* Now setup the page table */
-			for (i = 0; i < npages; i++)
-				kvm->arch.guest_pmap[i] = KVM_INVALID_PAGE;
-		}
-	}
 }
 
 static inline void dump_handler(const char *symbol, void *start, void *end)