[Xen-devel] [PATCH v2 08/17] x86/hvm: split I/O completion handling from state model

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

The state of in-flight I/O and how its completion will be handled are
logically separate and conflating the two makes the code unnecessarily
confusing.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c         |   42 +++++++++++++++++++++++++---------------
 xen/arch/x86/hvm/io.c          |    4 ++--
 xen/include/asm-x86/hvm/vcpu.h |   15 +++++++++-----
 3 files changed, 38 insertions(+), 23 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 799f0e7..916459a 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -415,31 +415,41 @@ static void hvm_io_assist(ioreq_t *p)
 {
     struct vcpu *curr = current;
     struct hvm_vcpu_io *vio = &curr->arch.hvm_vcpu.hvm_io;
-    enum hvm_io_state io_state;
 
     p->state = STATE_IOREQ_NONE;
 
-    io_state = vio->io_state;
-    vio->io_state = HVMIO_none;
-
-    switch ( io_state )
+    switch ( vio->io_state )
     {
     case HVMIO_awaiting_completion:
+    {
+        enum hvm_io_completion completion = vio->io_completion;
+
         vio->io_state = HVMIO_completed;
         vio->io_data = p->data;
+        vio->io_completion = HVMIO_no_completion;
+
+        switch ( completion )
+        {
+        case HVMIO_mmio_completion:
+            (void)handle_mmio();
+            break;
+
+        case HVMIO_pio_completion:
+            if ( vio->io_size == 4 ) /* Needs zero extension. */
+                guest_cpu_user_regs()->rax = (uint32_t)p->data;
+            else
+                memcpy(&guest_cpu_user_regs()->rax, &p->data, vio->io_size);
+
+            vio->io_state = HVMIO_none;
+            break;
+        default:
+            break;
+        }
+
         break;
-    case HVMIO_handle_mmio_awaiting_completion:
-        vio->io_state = HVMIO_completed;
-        vio->io_data = p->data;
-        (void)handle_mmio();
-        break;
-    case HVMIO_handle_pio_awaiting_completion:
-        if ( vio->io_size == 4 ) /* Needs zero extension. */
-            guest_cpu_user_regs()->rax = (uint32_t)p->data;
-        else
-            memcpy(&guest_cpu_user_regs()->rax, &p->data, vio->io_size);
-        break;
+    }
     default:
+        vio->io_state = HVMIO_none;
         break;
     }
 
diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index ee0ed82..5527988 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -93,7 +93,7 @@ int handle_mmio(void)
     if ( rc != X86EMUL_RETRY )
         vio->io_state = HVMIO_none;
     if ( vio->io_state == HVMIO_awaiting_completion )
-        vio->io_state = HVMIO_handle_mmio_awaiting_completion;
+        vio->io_completion = HVMIO_mmio_completion;
     else
         vio->mmio_access = (struct npfec){};
 
@@ -158,7 +158,7 @@ int handle_pio(uint16_t port, unsigned int size, int dir)
             return 0;
         /* Completion in hvm_io_assist() with no re-emulation required. */
         ASSERT(dir == IOREQ_READ);
-        vio->io_state = HVMIO_handle_pio_awaiting_completion;
+        vio->io_completion = HVMIO_pio_completion;
         break;
     default:
         gdprintk(XENLOG_ERR, "Weird HVM ioemulation status %d.\n", rc);
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index 97d78bd..87f9c8f 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -34,11 +34,15 @@ enum hvm_io_state {
     HVMIO_none = 0,
     HVMIO_dispatched,
     HVMIO_awaiting_completion,
-    HVMIO_handle_mmio_awaiting_completion,
-    HVMIO_handle_pio_awaiting_completion,
     HVMIO_completed
 };
 
+enum hvm_io_completion {
+    HVMIO_no_completion = 0,
+    HVMIO_mmio_completion,
+    HVMIO_pio_completion
+};
+
 struct hvm_vcpu_asid {
     uint64_t generation;
     uint32_t asid;
@@ -46,9 +50,10 @@ struct hvm_vcpu_asid {
 
 struct hvm_vcpu_io {
     /* I/O request in flight to device model. */
-    enum hvm_io_state   io_state;
-    unsigned long       io_data;
-    int                 io_size;
+    enum hvm_io_state      io_state;
+    unsigned long          io_data;
+    int                    io_size;
+    enum hvm_io_completion io_completion;
 
     /*
      * HVM emulation:
-- 
1.7.10.4


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