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, 8 insertions, 20 deletions

diff --git a/arch/mips/kvm/dyntrans.c b/arch/mips/kvm/dyntrans.c
index 010cef240688..60ebf5862d2b 100644
--- a/arch/mips/kvm/dyntrans.c
+++ b/arch/mips/kvm/dyntrans.c
@@ -13,6 +13,7 @@
 #include <linux/err.h>
 #include <linux/highmem.h>
 #include <linux/kvm_host.h>
+#include <linux/uaccess.h>
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
 #include <linux/bootmem.h>
@@ -29,28 +30,15 @@
 static int kvm_mips_trans_replace(struct kvm_vcpu *vcpu, u32 *opc,
 				  union mips_instruction replace)
 {
-	unsigned long paddr, flags;
-	void *vaddr;
-
-	if (KVM_GUEST_KSEGX((unsigned long)opc) == KVM_GUEST_KSEG0) {
-		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));
-		__local_flush_icache_user_range((unsigned long)opc,
-						(unsigned long)opc + 32);
-		local_irq_restore(flags);
-	} else {
+	unsigned long vaddr = (unsigned long)opc;
+	int err;
+
+	err = put_user(replace.word, opc);
+	if (unlikely(err)) {
 		kvm_err("%s: Invalid address: %p\n", __func__, opc);
-		return -EFAULT;
+		return err;
 	}
+	__local_flush_icache_user_range(vaddr, vaddr + 4);
 
 	return 0;
 }