KVM: 16-byte mmio support

Since sse instructions can issue 16-byte mmios, we need to support them.  We
can't increase the kvm_run mmio buffer size to 16 bytes without breaking
compatibility, so instead we break the large mmios into two smaller 8-byte
ones.  Since the bus is 64-bit we aren't breaking any atomicity guarantees.

Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 32 insertions, 10 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 35f81b110260..e820c6339b8b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -30,6 +30,7 @@
 #define KVM_MEMORY_SLOTS 32
 /* memory slots that does not exposed to userspace */
 #define KVM_PRIVATE_MEM_SLOTS 4
+#define KVM_MMIO_SIZE 16
 
 #define KVM_PIO_PAGE_OFFSET 1
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 2
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bb6b9d3f5e93..11d692c7018d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3833,8 +3833,10 @@ mmio:
         vcpu->mmio_needed = 1;
         vcpu->run->exit_reason = KVM_EXIT_MMIO;
         vcpu->run->mmio.phys_addr = vcpu->mmio_phys_addr = gpa;
-        vcpu->run->mmio.len = vcpu->mmio_size = bytes;
+        vcpu->mmio_size = bytes;
+        vcpu->run->mmio.len = min(vcpu->mmio_size, 8);
         vcpu->run->mmio.is_write = vcpu->mmio_is_write = 0;
+        vcpu->mmio_index = 0;
 
         return X86EMUL_IO_NEEDED;
 }
@@ -3886,11 +3888,14 @@ mmio:
         val += handled;
 
         vcpu->mmio_needed = 1;
+        memcpy(vcpu->mmio_data, val, bytes);
         vcpu->run->exit_reason = KVM_EXIT_MMIO;
         vcpu->run->mmio.phys_addr = vcpu->mmio_phys_addr = gpa;
-        vcpu->run->mmio.len = vcpu->mmio_size = bytes;
+        vcpu->mmio_size = bytes;
+        vcpu->run->mmio.len = min(vcpu->mmio_size, 8);
         vcpu->run->mmio.is_write = vcpu->mmio_is_write = 1;
-        memcpy(vcpu->run->mmio.data, val, bytes);
+        memcpy(vcpu->run->mmio.data, vcpu->mmio_data, 8);
+        vcpu->mmio_index = 0;
 
         return X86EMUL_CONTINUE;
 }
@@ -4498,11 +4503,9 @@ restart:
                 if (!vcpu->arch.pio.in)
                         vcpu->arch.pio.count = 0;
                 r = EMULATE_DO_MMIO;
-        } else if (vcpu->mmio_needed) {
-                if (vcpu->mmio_is_write)
-                        vcpu->mmio_needed = 0;
+        } else if (vcpu->mmio_needed)
                 r = EMULATE_DO_MMIO;
-        } else if (r == EMULATION_RESTART)
+        else if (r == EMULATION_RESTART)
                 goto restart;
         else
                 r = EMULATE_DONE;
@@ -5450,9 +5453,22 @@ static int complete_mmio(struct kvm_vcpu *vcpu)
                 return 1;
 
         if (vcpu->mmio_needed) {
-                memcpy(vcpu->mmio_data, run->mmio.data, 8);
-                vcpu->mmio_read_completed = 1;
                 vcpu->mmio_needed = 0;
+                if (!vcpu->mmio_is_write)
+                        memcpy(vcpu->mmio_data, run->mmio.data, 8);
+                vcpu->mmio_index += 8;
+                if (vcpu->mmio_index < vcpu->mmio_size) {
+                        run->exit_reason = KVM_EXIT_MMIO;
+                        run->mmio.phys_addr = vcpu->mmio_phys_addr + vcpu->mmio_index;
+                        memcpy(run->mmio.data, vcpu->mmio_data + vcpu->mmio_index, 8);
+                        run->mmio.len = min(vcpu->mmio_size - vcpu->mmio_index, 8);
+                        run->mmio.is_write = vcpu->mmio_is_write;
+                        vcpu->mmio_needed = 1;
+                        return 0;
+                }
+                if (vcpu->mmio_is_write)
+                        return 1;
+                vcpu->mmio_read_completed = 1;
         }
         vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
         r = emulate_instruction(vcpu, EMULTYPE_NO_DECODE);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7ca831e55186..d1f507567068 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -27,6 +27,10 @@
 
 #include <asm/kvm_host.h>
 
+#ifndef KVM_MMIO_SIZE
+#define KVM_MMIO_SIZE 8
+#endif
+
 /*
  * vcpu->requests bit members
  */
@@ -132,7 +136,8 @@ struct kvm_vcpu {
         int mmio_read_completed;
         int mmio_is_write;
         int mmio_size;
-        unsigned char mmio_data[8];
+        int mmio_index;
+        unsigned char mmio_data[KVM_MMIO_SIZE];
         gpa_t mmio_phys_addr;
 #endif