[PATCH v5 11/16] x86/hvm: split I/O completion handling from state model

[Paul Durrant <paul.durrant@citrix.com>]

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@citrix.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/hvm/hvm.c            |   44 +++++++++++++++++++++++++++----------
 xen/arch/x86/hvm/io.c             |    6 ++---
 xen/arch/x86/hvm/vmx/realmode.c   |   27 +++++++++++++++++------
 xen/include/asm-x86/hvm/vcpu.h    |   16 +++++++++-----
 xen/include/asm-x86/hvm/vmx/vmx.h |    1 +
 5 files changed, 67 insertions(+), 27 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index d498151..0f0730e 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -59,6 +59,7 @@
 #include <asm/hvm/trace.h>
 #include <asm/hvm/nestedhvm.h>
 #include <asm/hvm/event.h>
+#include <asm/hvm/vmx/vmx.h>
 #include <asm/mtrr.h>
 #include <asm/apic.h>
 #include <public/sched.h>
@@ -428,17 +429,6 @@ static void hvm_io_assist(ioreq_t *p)
         vio->io_state = HVMIO_completed;
         vio->io_data = p->data;
         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:
         break;
     }
@@ -479,6 +469,7 @@ void hvm_do_resume(struct vcpu *v)
     struct hvm_vcpu_io *vio = &v->arch.hvm_vcpu.hvm_io;
     struct domain *d = v->domain;
     struct hvm_ioreq_server *s;
+    enum hvm_io_completion io_completion;
 
     check_wakeup_from_wait();
 
@@ -505,8 +496,37 @@ void hvm_do_resume(struct vcpu *v)
         }
     }
 
-    if ( vio->mmio_retry )
+    io_completion = vio->io_completion;
+    vio->io_completion = HVMIO_no_completion;
+
+    switch ( io_completion )
+    {
+    case HVMIO_no_completion:
+        break;
+    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)vio->io_data;
+        else
+            memcpy(&guest_cpu_user_regs()->rax, &vio->io_data, vio->io_size);
+        vio->io_state = HVMIO_none;
+        break;
+    case HVMIO_realmode_completion:
+    {
+        struct hvm_emulate_ctxt ctxt;
+
+        hvm_emulate_prepare(&ctxt, guest_cpu_user_regs());
+        vmx_realmode_emulate_one(&ctxt);
+        hvm_emulate_writeback(&ctxt);
+
+        break;
+    }
+    default:
+        ASSERT_UNREACHABLE();
+        break;
+    }
 
     /* Inject pending hw/sw trap */
     if ( v->arch.hvm_vcpu.inject_trap.vector != -1 ) 
diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index fe099d8..221d05e 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -92,8 +92,8 @@ 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;
+    if ( vio->io_state == HVMIO_awaiting_completion || vio->mmio_retry )
+        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/arch/x86/hvm/vmx/realmode.c b/xen/arch/x86/hvm/vmx/realmode.c
index fe8b4a0..76ff9a5 100644
--- a/xen/arch/x86/hvm/vmx/realmode.c
+++ b/xen/arch/x86/hvm/vmx/realmode.c
@@ -101,15 +101,19 @@ static void realmode_deliver_exception(
     }
 }
 
-static void realmode_emulate_one(struct hvm_emulate_ctxt *hvmemul_ctxt)
+void vmx_realmode_emulate_one(struct hvm_emulate_ctxt *hvmemul_ctxt)
 {
     struct vcpu *curr = current;
+    struct hvm_vcpu_io *vio = &curr->arch.hvm_vcpu.hvm_io;
     int rc;
 
     perfc_incr(realmode_emulations);
 
     rc = hvm_emulate_one(hvmemul_ctxt);
 
+    if ( vio->io_state == HVMIO_awaiting_completion || vio->mmio_retry )
+        vio->io_completion = HVMIO_realmode_completion;
+
     if ( rc == X86EMUL_UNHANDLEABLE )
     {
         gdprintk(XENLOG_ERR, "Failed to emulate insn.\n");
@@ -177,9 +181,6 @@ void vmx_realmode(struct cpu_user_regs *regs)
 
     hvm_emulate_prepare(&hvmemul_ctxt, regs);
 
-    if ( vio->io_state == HVMIO_completed )
-        realmode_emulate_one(&hvmemul_ctxt);
-
     /* Only deliver interrupts into emulated real mode. */
     if ( !(curr->arch.hvm_vcpu.guest_cr[0] & X86_CR0_PE) &&
          (intr_info & INTR_INFO_VALID_MASK) )
@@ -190,8 +191,7 @@ void vmx_realmode(struct cpu_user_regs *regs)
 
     curr->arch.hvm_vmx.vmx_emulate = 1;
     while ( curr->arch.hvm_vmx.vmx_emulate &&
-            !softirq_pending(smp_processor_id()) &&
-            (vio->io_state == HVMIO_none) )
+            !softirq_pending(smp_processor_id()) )
     {
         /*
          * Check for pending interrupts only every 16 instructions, because
@@ -203,7 +203,10 @@ void vmx_realmode(struct cpu_user_regs *regs)
              hvm_local_events_need_delivery(curr) )
             break;
 
-        realmode_emulate_one(&hvmemul_ctxt);
+        vmx_realmode_emulate_one(&hvmemul_ctxt);
+
+        if ( vio->io_state != HVMIO_none || vio->mmio_retry )
+            break;
 
         /* Stop emulating unless our segment state is not safe */
         if ( curr->arch.hvm_vmx.vmx_realmode )
@@ -245,3 +248,13 @@ void vmx_realmode(struct cpu_user_regs *regs)
     if ( intr_info & INTR_INFO_VALID_MASK )
         __vmwrite(VM_ENTRY_INTR_INFO, intr_info);
 }
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index 2ed0606..efb373f 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -34,11 +34,16 @@ 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,
+    HVMIO_realmode_completion
+};
+
 struct hvm_vcpu_asid {
     uint64_t generation;
     uint32_t asid;
@@ -46,9 +51,10 @@ 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;
+    unsigned int           io_size;
+    enum hvm_io_completion io_completion;
 
     /*
      * HVM emulation:
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h b/xen/include/asm-x86/hvm/vmx/vmx.h
index 35f804a..c5f3d24 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -94,6 +94,7 @@ void vmx_asm_do_vmentry(void);
 void vmx_intr_assist(void);
 void noreturn vmx_do_resume(struct vcpu *);
 void vmx_vlapic_msr_changed(struct vcpu *v);
+void vmx_realmode_emulate_one(struct hvm_emulate_ctxt *hvmemul_ctxt);
 void vmx_realmode(struct cpu_user_regs *regs);
 void vmx_update_debug_state(struct vcpu *v);
 void vmx_update_exception_bitmap(struct vcpu *v);
-- 
1.7.10.4