MIPS: KVM: Use kmap instead of CKSEG0ADDR()

There are several unportable uses of CKSEG0ADDR() in MIPS KVM, which
implicitly assume that a host physical address will be in the low 512MB
of the physical address space (accessible in KSeg0). These assumptions
don't hold for highmem or on 64-bit kernels.

When interpreting the guest physical address when reading or overwriting
a trapping instruction, use kmap_atomic() to get a usable virtual
address to access guest memory, which is portable to 64-bit and highmem
kernels.
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
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/kvm/dyntrans.c

@@ -11,6 +11,7 @@
 
 #include <linux/errno.h>
 #include <linux/err.h>
+#include <linux/highmem.h>
 #include <linux/kvm_host.h>
 #include <linux/module.h>
 #include <linux/vmalloc.h>
@@ -29,14 +30,18 @@
 static int kvm_mips_trans_replace(struct kvm_vcpu *vcpu, u32 *opc,
 				  union mips_instruction replace)
 {
-	unsigned long kseg0_opc, flags;
+	unsigned long paddr, flags;
+	void *vaddr;
 
 	if (KVM_GUEST_KSEGX(opc) == KVM_GUEST_KSEG0) {
-		kseg0_opc =
-		    CKSEG0ADDR(kvm_mips_translate_guest_kseg0_to_hpa
-			       (vcpu, (unsigned long) opc));
-		memcpy((void *)kseg0_opc, (void *)&replace, sizeof(u32));
-		local_flush_icache_range(kseg0_opc, kseg0_opc + 32);
+		paddr = kvm_mips_translate_guest_kseg0_to_hpa(vcpu,
+							    (unsigned long)opc);
+		vaddr = kmap_atomic(pfn_to_page(PHYS_PFN(paddr)));
+		vaddr += paddr & ~PAGE_MASK;
+		memcpy(vaddr, (void *)&replace, sizeof(u32));
+		local_flush_icache_range((unsigned long)vaddr,
+					 (unsigned long)vaddr + 32);
+		kunmap_atomic(vaddr);
 	} else if (KVM_GUEST_KSEGX((unsigned long) opc) == KVM_GUEST_KSEG23) {
 		local_irq_save(flags);
 		memcpy((void *)opc, (void *)&replace, sizeof(u32));

arch/mips/kvm/mmu.c

@@ -9,6 +9,7 @@
  * Authors: Sanjay Lal <sanjayl@kymasys.com>
  */
 
+#include <linux/highmem.h>
 #include <linux/kvm_host.h>
 #include <asm/mmu_context.h>
 
@@ -330,6 +331,7 @@ u32 kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu)
 	struct mips_coproc *cop0 = vcpu->arch.cop0;
 	unsigned long paddr, flags, vpn2, asid;
 	unsigned long va = (unsigned long)opc;
+	void *vaddr;
 	u32 inst;
 	int index;
 
@@ -360,7 +362,10 @@ u32 kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu)
 		local_irq_restore(flags);
 	} else if (KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG0) {
 		paddr = kvm_mips_translate_guest_kseg0_to_hpa(vcpu, va);
-		inst = *(u32 *) CKSEG0ADDR(paddr);
+		vaddr = kmap_atomic(pfn_to_page(PHYS_PFN(paddr)));
+		vaddr += paddr & ~PAGE_MASK;
+		inst = *(u32 *)vaddr;
+		kunmap_atomic(vaddr);
 	} else {
 		kvm_err("%s: illegal address: %p\n", __func__, opc);
 		return KVM_INVALID_INST;