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Re: [Qemu-devel] [PATCH v4 1/1] xen-hvm.c: Add support for Xen access to


From: Don Slutz
Subject: Re: [Qemu-devel] [PATCH v4 1/1] xen-hvm.c: Add support for Xen access to vmport
Date: Fri, 17 Oct 2014 09:30:31 -0400
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0

On 10/17/14 08:34, Paul Durrant wrote:
-----Original Message-----
From: Don Slutz [mailto:address@hidden
Sent: 17 October 2014 13:14
To: address@hidden; Paul Durrant
Cc: address@hidden; Alexander Graf; Andreas Färber;
Anthony Liguori; Don Slutz; Marcel Apfelbaum; Markus Armbruster; Michael
S. Tsirkin; Stefano Stabellini
Subject: [PATCH v4 1/1] xen-hvm.c: Add support for Xen access to vmport

This adds synchronisation of the 6 vcpu registers (only 32bits of
them) that vmport.c needs between Xen and QEMU.

This is to avoid a 2nd and 3rd exchange between QEMU and Xen to
fetch and put these 6 vcpu registers used by the code in vmport.c
and vmmouse.c

The registers are passed in the new shared page provided by
HVM_PARAM_VMPORT_IOREQ_PFN.

Add new array to XenIOState that allows selection of current_cpu by
ioreq_id.

Now pass XenIOState to handle_ioreq().

Add new routines regs_to_cpu(), regs_from_cpu(), and
handle_vmport_ioreq().

Signed-off-by: Don Slutz <address@hidden>
---
  include/hw/xen/xen_common.h |  15 ++++++
  xen-hvm.c                   | 121
++++++++++++++++++++++++++++++++++++++++++--
  2 files changed, 131 insertions(+), 5 deletions(-)

diff --git a/include/hw/xen/xen_common.h
b/include/hw/xen/xen_common.h
index 07731b9..9542756 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -164,4 +164,19 @@ void destroy_hvm_domain(bool reboot);
  /* shutdown/destroy current domain because of an error */
  void xen_shutdown_fatal_error(const char *fmt, ...) GCC_FMT_ATTR(1, 2);

+#ifdef HVM_PARAM_VMPORT_IOREQ_PFN
+static inline int xen_get_vmport_ioreq_pfn(XenXC xc, domid_t dom,
+                                           unsigned long *vmport_ioreq_pfn)
+{
+    return xc_get_hvm_param(xc, dom,
HVM_PARAM_VMPORT_IOREQ_PFN,
+                            vmport_ioreq_pfn);
+}
+#else
+static inline int xen_get_vmport_ioreq_pfn(XenXC xc, domid_t dom,
+                                           unsigned long *vmport_ioreq_pfn)
+{
+    return -ENOSYS;
+}
+#endif
+
  #endif /* QEMU_HW_XEN_COMMON_H */
diff --git a/xen-hvm.c b/xen-hvm.c
index 05e522c..17b3cbd 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -41,6 +41,29 @@ static MemoryRegion *framebuffer;
  static bool xen_in_migration;

  /* Compatibility with older version */
+
+/* This allows QEMU to build on a system that has Xen 4.5 or earlier
+ * installed.  This here (not in hw/xen/xen_common.h) because
xen/hvm/ioreq.h
+ * needs to be included before this block and hw/xen/xen_common.h
needs to
+ * be included before xen/hvm/ioreq.h
+ */
+#ifndef IOREQ_TYPE_VMWARE_PORT
+#define IOREQ_TYPE_VMWARE_PORT  3
+struct vmware_ioreq {
+    uint32_t esi;
+    uint32_t edi;
+    uint32_t ebx;
+    uint32_t ecx;
+    uint32_t edx;
+};
+typedef struct vmware_ioreq vmware_ioreq_t;
This struct is not really a request any more. Maybe vmware_regs_t?

Sure.

+
+struct shared_vmport_iopage {
+    struct vmware_ioreq vcpu_vmport_ioreq[1];
+};
+typedef struct shared_vmport_iopage shared_vmport_iopage_t;
+#endif
+
  #if __XEN_LATEST_INTERFACE_VERSION__ < 0x0003020a
  static inline uint32_t xen_vcpu_eport(shared_iopage_t *shared_page, int i)
  {
@@ -79,8 +102,10 @@ typedef struct XenPhysmap {

  typedef struct XenIOState {
      shared_iopage_t *shared_page;
+    shared_vmport_iopage_t *shared_vmport_page;
      buffered_iopage_t *buffered_io_page;
      QEMUTimer *buffered_io_timer;
+    CPUState **cpu_by_ioreq_id;
This name implies the array is indexed by an id carries in the ioreq. That 
doesn't seem to be the case; it's just indexed by guest vcpu id isn't it?

Yes.  How about cpu_by_vcpu_id ?

      /* the evtchn port for polling the notification, */
      evtchn_port_t *ioreq_local_port;
      /* evtchn local port for buffered io */
@@ -101,6 +126,8 @@ typedef struct XenIOState {
      Notifier wakeup;
  } XenIOState;

+static void handle_ioreq(XenIOState *state, ioreq_t *req);
+
  /* Xen specific function for piix pci */

  int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num)
@@ -610,6 +637,20 @@ static ioreq_t
*cpu_get_ioreq_from_shared_memory(XenIOState *state, int vcpu)
      return req;
  }

+/* get the vmport ioreq packets from share mem */
+static vmware_ioreq_t *cpu_get_vmport_ioreq_from_shared_memory(
Is this worth its own function? I can only see one use of it in 
handle_vmport_ioreq below...

Will move it in-line.  I was just following
cpu_get_ioreq_from_shared_memory which also has 1 use.

+    XenIOState *state, int vcpu)
+{
+    vmware_ioreq_t *vmport_req;
+
+    assert(state->shared_vmport_page);
+    vmport_req = &state->shared_vmport_page-
vcpu_vmport_ioreq[vcpu];
+
+    xen_rmb(); /* see IOREQ_READY /then/ read contents of ioreq */
I don't think that comment is applicable here, and I don't think you need the 
barrier anyway.

I was not sure either way, so went with the safe way.  Will drop.

+
+    return vmport_req;
+}
+
  /* use poll to get the port notification */
  /* ioreq_vec--out,the */
  /* retval--the number of ioreq packet */
@@ -773,7 +814,50 @@ static void cpu_ioreq_move(ioreq_t *req)
      }
  }

-static void handle_ioreq(ioreq_t *req)
+static void regs_to_cpu(XenIOState *state, vmware_ioreq_t *vmport_req,
+                        ioreq_t *req)
+{
+    X86CPU *cpu;
+    CPUX86State *env;
+
+    current_cpu = state->cpu_by_ioreq_id[state->send_vcpu];
+    cpu = X86_CPU(current_cpu);
+    env = &cpu->env;
+    env->regs[R_EAX] = req->data;
+    env->regs[R_EBX] = vmport_req->ebx;
+    env->regs[R_ECX] = vmport_req->ecx;
+    env->regs[R_EDX] = vmport_req->edx;
+    env->regs[R_ESI] = vmport_req->esi;
+    env->regs[R_EDI] = vmport_req->edi;
+}
+
+static void regs_from_cpu(XenIOState *state, vmware_ioreq_t
*vmport_req,
+                          ioreq_t *req)
+{
+    X86CPU *cpu = X86_CPU(current_cpu);
+    CPUX86State *env = &cpu->env;
+
+    assert(sizeof(*vmport_req) <= sizeof(*req));
Why?

Since there is 1 page of ioreq_t indexed by vcpu id this checks that
the 1 page of vmport data has at least the same number of vcpu
slots.  This prevents a bad memory read.  Looks to not be the right place
for this, will move.

+
+    vmport_req->ebx = env->regs[R_EBX];
+    vmport_req->ecx = env->regs[R_ECX];
+    vmport_req->edx = env->regs[R_EDX];
+    vmport_req->esi = env->regs[R_ESI];
+    vmport_req->edi = env->regs[R_EDI];
+    current_cpu = NULL;
+}
+
+static void handle_vmport_ioreq(XenIOState *state, ioreq_t *req)
+{
+    vmware_ioreq_t *vmport_req =
+        cpu_get_vmport_ioreq_from_shared_memory(state, state-
send_vcpu);
+
+    regs_to_cpu(state, vmport_req, req);
+    cpu_ioreq_pio(req);
+    regs_from_cpu(state, vmport_req, req);
state appears to be unused in this function, and you could avoid passing it to 
both of them by setting current_cpu here couldn't you?

Yes, will move state code here.

   -Don Slutz

   Paul

+}
+
+static void handle_ioreq(XenIOState *state, ioreq_t *req)
  {
      if (!req->data_is_ptr && (req->dir == IOREQ_WRITE) &&
              (req->size < sizeof (target_ulong))) {
@@ -787,6 +871,9 @@ static void handle_ioreq(ioreq_t *req)
          case IOREQ_TYPE_COPY:
              cpu_ioreq_move(req);
              break;
+        case IOREQ_TYPE_VMWARE_PORT:
+            handle_vmport_ioreq(state, req);
+            break;
          case IOREQ_TYPE_TIMEOFFSET:
              break;
          case IOREQ_TYPE_INVALIDATE:
@@ -828,7 +915,7 @@ static int handle_buffered_iopage(XenIOState
*state)
              req.data |= ((uint64_t)buf_req->data) << 32;
          }

-        handle_ioreq(&req);
+        handle_ioreq(state, &req);

          xen_mb();
          state->buffered_io_page->read_pointer += qw ? 2 : 1;
@@ -857,14 +944,16 @@ static void cpu_handle_ioreq(void *opaque)

      handle_buffered_iopage(state);
      if (req) {
-        handle_ioreq(req);
+        handle_ioreq(state, req);

          if (req->state != STATE_IOREQ_INPROCESS) {
              fprintf(stderr, "Badness in I/O request ... not in service?!: "
                      "%x, ptr: %x, port: %"PRIx64", "
-                    "data: %"PRIx64", count: %" FMT_ioreq_size ", size: %"
FMT_ioreq_size "\n",
+                    "data: %"PRIx64", count: %" FMT_ioreq_size
+                    ", size: %" FMT_ioreq_size
+                    ", type: %"FMT_ioreq_size"\n",
                      req->state, req->data_is_ptr, req->addr,
-                    req->data, req->count, req->size);
+                    req->data, req->count, req->size, req->type);
              destroy_hvm_domain(false);
              return;
          }
@@ -904,6 +993,14 @@ static void xen_main_loop_prepare(XenIOState
*state)
                                                   state);

      if (evtchn_fd != -1) {
+        CPUState *cpu_state;
+
+        DPRINTF("%s: Init cpu_by_ioreq_id\n", __func__);
+        CPU_FOREACH(cpu_state) {
+            DPRINTF("%s: cpu_by_ioreq_id[%d]=%p\n",
+                    __func__, cpu_state->cpu_index, cpu_state);
+            state->cpu_by_ioreq_id[cpu_state->cpu_index] = cpu_state;
+        }
          qemu_set_fd_handler(evtchn_fd, cpu_handle_ioreq, NULL, state);
      }
  }
@@ -1020,6 +1117,17 @@ int xen_hvm_init(ram_addr_t
*below_4g_mem_size, ram_addr_t *above_4g_mem_size,
                   errno, xen_xc);
      }

+    if (!xen_get_vmport_ioreq_pfn(xen_xc, xen_domid, &ioreq_pfn)) {
+        DPRINTF("shared vmport page at pfn %lx\n", ioreq_pfn);
+        state->shared_vmport_page =
+            xc_map_foreign_range(xen_xc, xen_domid, XC_PAGE_SIZE,
+                                 PROT_READ|PROT_WRITE, ioreq_pfn);
+        if (state->shared_vmport_page == NULL) {
+            hw_error("map shared vmport IO page returned error %d handle="
+                     XC_INTERFACE_FMT, errno, xen_xc);
+        }
+    }
+
      xc_get_hvm_param(xen_xc, xen_domid, HVM_PARAM_BUFIOREQ_PFN,
&ioreq_pfn);
      DPRINTF("buffered io page at pfn %lx\n", ioreq_pfn);
      state->buffered_io_page = xc_map_foreign_range(xen_xc, xen_domid,
XC_PAGE_SIZE,
@@ -1028,6 +1136,9 @@ int xen_hvm_init(ram_addr_t
*below_4g_mem_size, ram_addr_t *above_4g_mem_size,
          hw_error("map buffered IO page returned error %d", errno);
      }

+    /* Note: cpus is empty at this point in init */
+    state->cpu_by_ioreq_id = g_malloc0(max_cpus * sizeof(CPUState *));
+
      state->ioreq_local_port = g_malloc0(max_cpus * sizeof (evtchn_port_t));

      /* FIXME: how about if we overflow the page here? */
--
1.8.4




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