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

[Stefano Stabellini]

Your patch is simpler and more mature. Maybe it should go in before Gerd's
series?

On Thu, 7 Jan 2016, Cao jin wrote:
> 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
> 
> 
>