KVM: MIPS: Use uaccess to read/modify guest instructions

Now that we have GVA page tables, use standard user accesses with page
faults disabled to read & modify guest instructions. This should be more
robust (than the rather dodgy method of accessing guest mapped segments
by just directly addressing them) and will also work with Enhanced
Virtual Addressing (EVA) host kernel configurations where dedicated
instructions are needed for accessing user mode memory.

For simplicity and speed we do this regardless of the guest segment the
address resides in, rather than handling guest KSeg0 specially with
kmap_atomic() as before.

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, 5 insertions, 72 deletions

diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
index 98f1a7715a68..c4e9c65065ea 100644
--- a/arch/mips/kvm/mmu.c
+++ b/arch/mips/kvm/mmu.c
@@ -11,6 +11,7 @@
 
 #include <linux/highmem.h>
 #include <linux/kvm_host.h>
+#include <linux/uaccess.h>
 #include <asm/mmu_context.h>
 #include <asm/pgalloc.h>
 
@@ -134,34 +135,6 @@ out:
 	return err;
 }
 
-/* Translate guest KSEG0 addresses to Host PA */
-unsigned long kvm_mips_translate_guest_kseg0_to_hpa(struct kvm_vcpu *vcpu,
-						    unsigned long gva)
-{
-	gfn_t gfn;
-	unsigned long offset = gva & ~PAGE_MASK;
-	struct kvm *kvm = vcpu->kvm;
-
-	if (KVM_GUEST_KSEGX(gva) != KVM_GUEST_KSEG0) {
-		kvm_err("%s/%p: Invalid gva: %#lx\n", __func__,
-			__builtin_return_address(0), gva);
-		return KVM_INVALID_PAGE;
-	}
-
-	gfn = (KVM_GUEST_CPHYSADDR(gva) >> PAGE_SHIFT);
-
-	if (gfn >= kvm->arch.guest_pmap_npages) {
-		kvm_err("%s: Invalid gfn: %#llx, GVA: %#lx\n", __func__, gfn,
-			gva);
-		return KVM_INVALID_PAGE;
-	}
-
-	if (kvm_mips_map_page(vcpu->kvm, gfn) < 0)
-		return KVM_INVALID_ADDR;
-
-	return (kvm->arch.guest_pmap[gfn] << PAGE_SHIFT) + offset;
-}
-
 static pte_t *kvm_trap_emul_pte_for_gva(struct kvm_vcpu *vcpu,
 					unsigned long addr)
 {
@@ -551,51 +524,11 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 
 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;
-
-	if (KVM_GUEST_KSEGX(va) < KVM_GUEST_KSEG0 ||
-	    KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG23) {
-		local_irq_save(flags);
-		index = kvm_mips_host_tlb_lookup(vcpu, va);
-		if (index >= 0) {
-			inst = *(opc);
-		} else {
-			vpn2 = va & VPN2_MASK;
-			asid = kvm_read_c0_guest_entryhi(cop0) &
-						KVM_ENTRYHI_ASID;
-			index = kvm_mips_guest_tlb_lookup(vcpu, vpn2 | asid);
-			if (index < 0) {
-				kvm_err("%s: get_user_failed for %p, vcpu: %p, ASID: %#lx\n",
-					__func__, opc, vcpu, read_c0_entryhi());
-				kvm_mips_dump_host_tlbs();
-				kvm_mips_dump_guest_tlbs(vcpu);
-				local_irq_restore(flags);
-				return KVM_INVALID_INST;
-			}
-			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu,
-					&vcpu->arch.guest_tlb[index], va)) {
-				kvm_err("%s: handling mapped seg tlb fault failed for %p, index: %u, vcpu: %p, ASID: %#lx\n",
-					__func__, opc, index, vcpu,
-					read_c0_entryhi());
-				kvm_mips_dump_guest_tlbs(vcpu);
-				local_irq_restore(flags);
-				return KVM_INVALID_INST;
-			}
-			inst = *(opc);
-		}
-		local_irq_restore(flags);
-	} else if (KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG0) {
-		paddr = kvm_mips_translate_guest_kseg0_to_hpa(vcpu, va);
-		vaddr = kmap_atomic(pfn_to_page(PHYS_PFN(paddr)));
-		vaddr += paddr & ~PAGE_MASK;
-		inst = *(u32 *)vaddr;
-		kunmap_atomic(vaddr);
-	} else {
+	int err;
+
+	err = get_user(inst, opc);
+	if (unlikely(err)) {
 		kvm_err("%s: illegal address: %p\n", __func__, opc);
 		return KVM_INVALID_INST;
 	}