| Message ID | 1451994098-6972-8-git-send-email-kraxel@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 5 Jan 2016, Gerd Hoffmann wrote: > Move all work to the host_pci_config_copy helper function, > which we can easily reuse when adding q35 support. > Open sysfs file only once for all values. Use pread. > Proper error handling. Fix bugs: > > * Don't throw away results (like old host_pci_config_read > did because val was passed by value not reference). > * Update config space directly (writing via > pci_default_write_config only works for registers > whitelisted in wmask). > > Hmm, this code can hardly ever worked before, > /me wonders what test coverage it had. > > With this patch in place igd-passthru=on actually > works, although it still requires root priviledges > because linux refuses to allow non-root users access > pci config space above offset 0x50. > > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> > --- > hw/pci-host/igd.c | 65 +++++++++++++++++++++++-------------------------------- > 1 file changed, 27 insertions(+), 38 deletions(-) > > diff --git a/hw/pci-host/igd.c b/hw/pci-host/igd.c > index 0784128..ec48875 100644 > --- a/hw/pci-host/igd.c > +++ b/hw/pci-host/igd.c > @@ -19,47 +19,39 @@ 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_copy(PCIDevice *guest, const char *host, > + const IGDHostInfo *list, int len, Error **errp) > { > - char path[PATH_MAX]; > - int config_fd; > - ssize_t size = sizeof(path); > - /* 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; > + char *path; > + int config_fd, rc, i; > > - if (rc >= size || rc < 0) { > - return -ENODEV; > - } > - > - config_fd = open(path, O_RDWR); > + path = g_strdup_printf("/sys/bus/pci/devices/%s/config", host); > + config_fd = open(path, O_RDONLY); > if (config_fd < 0) { > - return -ENODEV; > + error_setg_file_open(errp, errno, path); > + goto out_free; > } > > - if (lseek(config_fd, pos, SEEK_SET) != pos) { > - ret = -errno; > - goto out; > + for (i = 0; i < len; i++) { > + rc = pread(config_fd, guest->config + list[i].offset, > + list[i].len, list[i].offset); > + if (rc != list[i].len) { pread is allowed to return early, returning the number of bytes read. > + error_setg_errno(errp, errno, "read %s, offset 0x%x", > + path, list[i].offset); > + goto out_close; > + } > } > - do { > - rc = read(config_fd, (uint8_t *)&val, len); > - } while (rc < 0 && (errno == EINTR || errno == EAGAIN)); > - if (rc != len) { > - ret = -errno; > - } > -out: > + > +out_close: > close(config_fd); > - return ret; > +out_free: > + g_free(path); > } > > static void (*i440fx_realize)(PCIDevice *pci_dev, Error **errp); > static void igd_pt_i440fx_realize(PCIDevice *pci_dev, Error **errp) > { > Error *err = NULL; > - uint32_t val = 0; > - int rc, i, num; > - int pos, len; > > i440fx_realize(pci_dev, &err); > if (err != NULL) { > @@ -67,16 +59,13 @@ static void igd_pt_i440fx_realize(PCIDevice *pci_dev, Error **errp) > return; > } > > - 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) { > - error_setg(errp, "failed to read host config"); > - return; > - } > - pci_default_write_config(pci_dev, pos, val, len); > + host_pci_config_copy(pci_dev, "0000:00:00.0", > + igd_host_bridge_infos, > + ARRAY_SIZE(igd_host_bridge_infos), > + &err); > + if (err != NULL) { > + error_propagate(errp, err); > + return; > } > } > > -- > 1.8.3.1 >
> > + for (i = 0; i < len; i++) { > > + rc = pread(config_fd, guest->config + list[i].offset, > > + list[i].len, list[i].offset); > > + if (rc != list[i].len) { > > pread is allowed to return early, returning the number of bytes read. > This is a sysfs file though, not a socket or pipe where a partial read makes sense and will actually happen. If we can't read something that'll be because the kernel denies access. So IMHO it should be fine to treat anything which doesn't give us the amount of bytes we asked for as an error condition. cheers, Gerd
On Wed, 6 Jan 2016, Gerd Hoffmann wrote: > > > + for (i = 0; i < len; i++) { > > > + rc = pread(config_fd, guest->config + list[i].offset, > > > + list[i].len, list[i].offset); > > > + if (rc != list[i].len) { > > > > pread is allowed to return early, returning the number of bytes read. > > > > This is a sysfs file though, not a socket or pipe where a partial read > makes sense and will actually happen. If we can't read something > that'll be because the kernel denies access. > > So IMHO it should be fine to treat anything which doesn't give us the > amount of bytes we asked for as an error condition. True, still theoretically, it's possible for pread to return early. Who knows what glibc and linux are going to do in the future.
diff --git a/hw/pci-host/igd.c b/hw/pci-host/igd.c index 0784128..ec48875 100644 --- a/hw/pci-host/igd.c +++ b/hw/pci-host/igd.c @@ -19,47 +19,39 @@ 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_copy(PCIDevice *guest, const char *host, + const IGDHostInfo *list, int len, Error **errp) { - char path[PATH_MAX]; - int config_fd; - ssize_t size = sizeof(path); - /* 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; + char *path; + int config_fd, rc, i; - if (rc >= size || rc < 0) { - return -ENODEV; - } - - config_fd = open(path, O_RDWR); + path = g_strdup_printf("/sys/bus/pci/devices/%s/config", host); + config_fd = open(path, O_RDONLY); if (config_fd < 0) { - return -ENODEV; + error_setg_file_open(errp, errno, path); + goto out_free; } - if (lseek(config_fd, pos, SEEK_SET) != pos) { - ret = -errno; - goto out; + for (i = 0; i < len; i++) { + rc = pread(config_fd, guest->config + list[i].offset, + list[i].len, list[i].offset); + if (rc != list[i].len) { + error_setg_errno(errp, errno, "read %s, offset 0x%x", + path, list[i].offset); + goto out_close; + } } - do { - rc = read(config_fd, (uint8_t *)&val, len); - } while (rc < 0 && (errno == EINTR || errno == EAGAIN)); - if (rc != len) { - ret = -errno; - } -out: + +out_close: close(config_fd); - return ret; +out_free: + g_free(path); } static void (*i440fx_realize)(PCIDevice *pci_dev, Error **errp); static void igd_pt_i440fx_realize(PCIDevice *pci_dev, Error **errp) { Error *err = NULL; - uint32_t val = 0; - int rc, i, num; - int pos, len; i440fx_realize(pci_dev, &err); if (err != NULL) { @@ -67,16 +59,13 @@ static void igd_pt_i440fx_realize(PCIDevice *pci_dev, Error **errp) return; } - 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) { - error_setg(errp, "failed to read host config"); - return; - } - pci_default_write_config(pci_dev, pos, val, len); + host_pci_config_copy(pci_dev, "0000:00:00.0", + igd_host_bridge_infos, + ARRAY_SIZE(igd_host_bridge_infos), + &err); + if (err != NULL) { + error_propagate(errp, err); + return; } }
Move all work to the host_pci_config_copy helper function, which we can easily reuse when adding q35 support. Open sysfs file only once for all values. Use pread. Proper error handling. Fix bugs: * Don't throw away results (like old host_pci_config_read did because val was passed by value not reference). * Update config space directly (writing via pci_default_write_config only works for registers whitelisted in wmask). Hmm, this code can hardly ever worked before, /me wonders what test coverage it had. With this patch in place igd-passthru=on actually works, although it still requires root priviledges because linux refuses to allow non-root users access pci config space above offset 0x50. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> --- hw/pci-host/igd.c | 65 +++++++++++++++++++++++-------------------------------- 1 file changed, 27 insertions(+), 38 deletions(-)