Re: [Qemu-devel] [Xen-devel] [PATCH V10 3/8] Introduce XenHostPCIDevice to access a pci device on the host.

[Anthony PERARD]

On Wed, Mar 28, 2012 at 19:52, Konrad Rzeszutek Wilk
<address@hidden> wrote:
>> +static int xen_host_pci_sysfs_path(const XenHostPCIDevice *d,
>> +                                   const char *name, char *buf, ssize_t 
>> size)
>> +{
>> +    int rc;
>> +
>> +    rc = snprintf(buf, size, "/sys/bus/pci/devices/%04x:%02x:%02x.%x/%s",
>
> The format is actually " %04x:%02x:%02x.%d"
>
>> +                  d->domain, d->bus, d->dev, d->func, name);
>> +
>> +    if (rc >= size || rc < 0) {
>> +        /* The ouput is truncated or an other error is encountered */
>> +        return -1;
>
> -ENODEV
>
>> +    }
>> +    return 0;
>> +}
>> +
>> +static int xen_host_pci_get_resource(XenHostPCIDevice *d)
>> +{
>> +    int i, rc, fd;
>> +    char path[PATH_MAX];
>> +    char buf[512];
>
> You should have a #define for the 512.
>
>> +    unsigned long long start, end, flags, size;
>> +    char *endptr, *s;
>> +
>> +    if (xen_host_pci_sysfs_path(d, "resource", path, sizeof (path))) {
>> +        return -1;
>
> -ENODEV

I still does not understand why return ENODEV (No such device) when an
error occure. Is it the better way to say that a device does not
behave like it should, or that a "module" using a device encounter any
kind of error that prevent it to use the device ?


>> +    }
>> +    fd = open(path, O_RDONLY);
>> +    if (fd == -1) {
>> +        XEN_HOST_PCI_LOG("Error: Can't open %s: %s\n", path, 
>> strerror(errno));
>> +        return -errno;
>> +    }
>> +
>> +    do {
>> +        rc = read(fd, &buf, sizeof (buf));
>> +        if (rc < 0 && errno != EINTR) {
>> +            rc = -errno;
>
> So you are using the errnor types, so you should use them throughout
> this function.
>
>> +            goto out;
>> +        }
>> +    } while (rc < 0);
>> +    buf[rc] = 0;
>> +    rc = 0;
>> +
>> +    s = buf;
>> +    for (i = 0; i < PCI_NUM_REGIONS; i++) {
>> +        start = strtoll(s, &endptr, 16);
>> +        if (*endptr != ' ' || s == endptr) {
>> +            break;
>> +        }
>> +        s = endptr + 1;
>> +        end = strtoll(s, &endptr, 16);
>> +        if (*endptr != ' ' || s == endptr) {
>> +            break;
>> +        }
>> +        s = endptr + 1;
>> +        flags = strtoll(s, &endptr, 16);
>> +        if (*endptr != '\n' || s == endptr) {
>> +            break;
>> +        }
>> +        s = endptr + 1;
>> +
>> +        if (start) {
>> +            size = end - start + 1;
>> +        } else {
>> +            size = 0;
>> +        }
>> +
>> +        if (i < PCI_ROM_SLOT) {
>> +            d->io_regions[i].base_addr = start;
>> +            d->io_regions[i].size = size;
>> +            d->io_regions[i].flags = flags;
>> +        } else {
>> +            d->rom.base_addr = start;
>> +            d->rom.size = size;
>> +            d->rom.flags = flags;
>> +        }
>> +    }
>> +    if (i != PCI_NUM_REGIONS) {
>> +        rc = -1;
>
> -ENODEV
>
>
>> +    }
>> +
>> +out:
>> +    close(fd);
>> +    return rc;
>> +}
>> +
>> +static int xen_host_pci_get_value(XenHostPCIDevice *d, const char *name,
>> +                                  unsigned int *pvalue, int base)
>> +{
>> +    char path[PATH_MAX];
>> +    char buf[42];
>
> You should use a #define
>
>> +    int fd, rc;
>> +    unsigned long value;
>> +    char *endptr;
>> +
>> +    if (xen_host_pci_sysfs_path(d, name, path, sizeof (path))) {
>> +        return -1;
>
> -ENODEV
>
>> +    }
>> +    fd = open(path, O_RDONLY);
>> +    if (fd == -1) {
>> +        XEN_HOST_PCI_LOG("Error: Can't open %s: %s\n", path, 
>> strerror(errno));
>> +        return -errno;
>> +    }
>> +    do {
>> +        rc = read(fd, &buf, sizeof (buf) - 1);
>
> Here you have sizeof(buf) - 1, but in the function 
> xen_host_pci_get_resource(..)
> you didn't do that. Any particular reason?

Nop, it's just a mistake.

>> +        if (rc < 0 && errno != EINTR) {
>> +            rc = -errno;
>> +            goto out;
>> +        }
>> +    } while (rc < 0);
>> +    buf[rc] = 0;
>> +    value = strtol(buf, &endptr, base);
>> +    if (endptr == buf || *endptr != '\n') {
>> +        rc = -1;
>
> ??? -Exx something I think
>
>> +    } else if ((value == LONG_MIN || value == LONG_MAX) && errno == ERANGE) 
>> {
>> +        rc = -errno;
>> +    } else {
>> +        rc = 0;
>> +        *pvalue = value;
>> +    }
>> +out:
>> +    close(fd);
>> +    return rc;
>> +}
>> +
>> +static inline int xen_host_pci_get_hex_value(XenHostPCIDevice *d,
>> +                                             const char *name,
>> +                                             unsigned int *pvalue)
>> +{
>> +    return xen_host_pci_get_value(d, name, pvalue, 16);
>> +}
>> +
>> +static inline int xen_host_pci_get_dec_value(XenHostPCIDevice *d,
>> +                                             const char *name,
>> +                                             unsigned int *pvalue)
>> +{
>> +    return xen_host_pci_get_value(d, name, pvalue, 10);
>> +}
>> +
>> +static bool xen_host_pci_dev_is_virtfn(XenHostPCIDevice *d)
>> +{
>> +    char path[PATH_MAX];
>> +    struct stat buf;
>> +
>> +    if (xen_host_pci_sysfs_path(d, "physfn", path, sizeof (path))) {
>> +        return false;
>> +    }
>> +    return !stat(path, &buf);
>> +}
>> +
>> +static int xen_host_pci_config_open(XenHostPCIDevice *d)
>> +{
>> +    char path[PATH_MAX];
>> +
>> +    if (xen_host_pci_sysfs_path(d, "config", path, sizeof (path))) {
>> +        return -1;
>
> -ENODEV
>
>> +    }
>> +    d->config_fd = open(path, O_RDWR);
>> +    if (d->config_fd < 0) {
>> +        return -errno;
>> +    }
>> +    return 0;
>> +}

[...]

>> +int xen_host_pci_find_ext_cap_offset(XenHostPCIDevice *d, uint32_t cap)
>> +{
>> +    uint32_t header = 0;
>> +    int max_cap = XEN_HOST_PCI_MAX_EXT_CAP;
>> +    int pos = PCI_CONFIG_SPACE_SIZE;
>> +
>> +    do {
>> +        if (xen_host_pci_get_long(d, pos, &header)) {
>> +            break;
>> +        }
>> +        /*
>> +         * If we have no capabilities, this is indicated by cap ID,
>> +         * cap version and next pointer all being 0.
>> +         */
>> +        if (header == 0) {
>> +            break;
>> +        }
>> +
>> +        if (PCI_EXT_CAP_ID(header) == cap) {
>> +            return pos;
>> +        }
>> +
>> +        pos = PCI_EXT_CAP_NEXT(header);
>> +        if (pos < PCI_CONFIG_SPACE_SIZE) {
>> +            break;
>> +        }
>> +
>> +        max_cap--;
>> +    } while (max_cap > 0);
>> +
>> +    return 0;
>
> If we fail in this function (which can happen 
> [https://bugzilla.redhat.com/show_bug.cgi?id=767742])
> shouldn't this function return something else besides 0?

-1 should be good enough, as it's not an offset.

> Besides those comments, the patch looks good to me.

Thanks,

-- 
Anthony PERARD