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Re: [Qemu-devel] [PATCH v4] igd-passthrough-i440FX: convert to realize()


From: Cao jin
Subject: Re: [Qemu-devel] [PATCH v4] igd-passthrough-i440FX: convert to realize()
Date: Thu, 7 Jan 2016 21:28:36 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0

Hi
Since Gerd has a whole patchset that covers this, Shall I continue with a new version of this?

On 12/29/2015 07:25 PM, Michael S. Tsirkin wrote:
On Tue, Dec 29, 2015 at 04:46:03PM +0800, Cao jin wrote:
Signed-off-by: Cao jin <address@hidden>
---
changelog v4:
1. strip the bugfix code, but I guess this patch should be applied after
    that bugfix patch.
2. Other little fix as per previous review

Some explanation to previous review:
1. error_setg_errno() I use in this patch will print the strerror(errno), so I
    guess it will be informative enough? example:

    error_setg_errno(errp, errno, "open %s fail", path); will print:
    "open bluhbluh fail: string_from_strerrer(errno)"

I'd prefer some mention of why this is attempted too.
E.g. "igd passthrough : open bluhbluh fail"

2. snprintf() has tiny tiny chance to fail,

It just formats a string into a buffer. the buffer
is pre-allocated, and we know it's large enough for the data.
How can it fail?


I don`t assert here, because this
    device is on-board, it init during machine initialization, in case it fails,
    the errp we set will results in error_report(err) and exit(1), at least can
    let user know why fail. see the call-chain:

    pc_xen_hvm_init_pci->pc_init1->i440fx_init->pci_create_simple-> 
pci_create_simple_multifunction->qdev_init_nofail

unlike open failing, there's nothing user can do, this means there's
a coding bug somewhere, and assert is easier to debug.

About test:
1. Compiled
2. Did a dirty hack to force create/realize this device in pc_init1(), prove
    that the realizing process is ok, I will reply this mail later to attch the
    screenshot evidence

Good job, thanks!
You should also Cc Tiejun Chen <address@hidden> who wrote this
code, presumably with access to hardware to test on.


  hw/pci-host/piix.c | 30 +++++++++++++++---------------
  1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index a9cb983..e91570f 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
      {0xa8, 4},  /* SNB: base of GTT stolen memory */
  };

-static int host_pci_config_read(int pos, int len, uint32_t *val)
+static void host_pci_config_read(int pos, int len, uint32_t *val, Error **errp)
  {
      char path[PATH_MAX];
      int config_fd;
@@ -769,19 +769,19 @@ static int host_pci_config_read(int pos, int len, 
uint32_t *val)
      /* Access real host bridge. */
      int rc = snprintf(path, size, "/sys/bus/pci/devices/%04x:%02x:%02x.%d/%s",
                        0, 0, 0, 0, "config");
-    int ret = 0;

      if (rc >= size || rc < 0) {
-        return -ENODEV;
+        error_setg_errno(errp, errno, "snprintf err");
      }

      config_fd = open(path, O_RDWR);
      if (config_fd < 0) {
-        return -ENODEV;
+        error_setg_errno(errp, errno, "open %s fail", path);
+        return;
      }

      if (lseek(config_fd, pos, SEEK_SET) != pos) {
-        ret = -errno;
+        error_setg_errno(errp, errno, "lseek err");
          goto out;
      }

@@ -789,32 +789,32 @@ static int host_pci_config_read(int pos, int len, 
uint32_t *val)
          rc = read(config_fd, (uint8_t *)val, len);
      } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
      if (rc != len) {
-        ret = -errno;
+        error_setg_errno(errp, errno, "read err");
      }

  out:
      close(config_fd);
-    return ret;
  }

-static int igd_pt_i440fx_initfn(struct PCIDevice *pci_dev)
+static void igd_pt_i440fx_realize(struct PCIDevice *pci_dev, Error **errp)
  {
      uint32_t val = 0;
-    int rc, i, num;
+    int i, num;
      int pos, len;
+    Error *local_err = NULL;

      num = ARRAY_SIZE(igd_host_bridge_infos);
      for (i = 0; i < num; i++) {
          pos = igd_host_bridge_infos[i].offset;
          len = igd_host_bridge_infos[i].len;
-        rc = host_pci_config_read(pos, len, &val);
-        if (rc) {
-            return -ENODEV;
+
+        host_pci_config_read(pos, len, &val, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return;
          }
          pci_default_write_config(pci_dev, pos, cpu_to_le32(val), len);
      }
-
-    return 0;
  }

  static void igd_passthrough_i440fx_class_init(ObjectClass *klass, void *data)
@@ -822,7 +822,7 @@ static void igd_passthrough_i440fx_class_init(ObjectClass 
*klass, void *data)
      DeviceClass *dc = DEVICE_CLASS(klass);
      PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);

-    k->init = igd_pt_i440fx_initfn;
+    k->realize = igd_pt_i440fx_realize;
      dc->desc = "IGD Passthrough Host bridge";
  }

--
2.1.0




.


--
Yours Sincerely,

Cao jin





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