On 7/22/2025 7:13 PM, Greg Kroah-Hartman wrote:
6.12-stable review patch. If anyone has any objections, please let me know.
From: Naman Jain namjain@linux.microsoft.com
commit a4131a50d072b369bfed0b41e741c41fd8048641 upstream.
Size of ring buffer, as defined in uio_hv_generic driver, is no longer fixed to 16 KB. This creates a problem in fcopy, since this size was hardcoded. With the change in place to make ring sysfs node actually reflect the size of underlying ring buffer, it is safe to get the size of ring sysfs file and use it for ring buffer size in fcopy daemon. Fix the issue of disparity in ring buffer size, by making it dynamic in fcopy uio daemon.
Cc: stable@vger.kernel.org Fixes: 0315fef2aff9 ("uio_hv_generic: Align ring size to system page") Signed-off-by: Naman Jain namjain@linux.microsoft.com Reviewed-by: Saurabh Sengar ssengar@linux.microsoft.com Reviewed-by: Long Li longli@microsoft.com Link: https://lore.kernel.org/r/20250711060846.9168-1-namjain@linux.microsoft.com Signed-off-by: Wei Liu wei.liu@kernel.org Message-ID: 20250711060846.9168-1-namjain@linux.microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Hello Greg, Please don't pick this change yet. I have shared the reason in the other thread: "Re: Patch "tools/hv: fcopy: Fix irregularities with size of ring buffer" has been added to the 6.12-stable tree"
Pasting it here: This patch depends on my older patch [1] which makes sure that the size of the ring sysfs node actually reflects the underlying ring buffer size.
[1] could not be ported on 6.12 and older kernels because of missing dependencies [2] and [3]. With kernel change [4] being backported to 6.12 kernel, FCopy is currently broken which I was trying to address with my patch.
Adding Thomas as well if its possible to port these patches on older kernels.
However for 6.6 and older kernels, fcopy is not working for me even without [4], which I am trying to debug.
------------ [1] 65995e97a1ca ("Drivers: hv: Make the sysfs node size for the ring buffer dynamic")
[2] 0afcee132bbc ("sysfs: explicitly pass size to sysfs_add_bin_file_mode_ns()")
[3] bebf29b18f34 ("sysfs: introduce callback attribute_group::bin_size")
[4] 0315fef2aff9 ("uio_hv_generic: Align ring size to system page")
Regards, Naman
tools/hv/hv_fcopy_uio_daemon.c | 91 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 81 insertions(+), 10 deletions(-)
--- a/tools/hv/hv_fcopy_uio_daemon.c +++ b/tools/hv/hv_fcopy_uio_daemon.c @@ -35,7 +35,10 @@ #define WIN8_SRV_MINOR 1 #define WIN8_SRV_VERSION (WIN8_SRV_MAJOR << 16 | WIN8_SRV_MINOR) -#define FCOPY_UIO "/sys/bus/vmbus/devices/eb765408-105f-49b6-b4aa-c123b64d17d4/uio" +#define FCOPY_DEVICE_PATH(subdir) \
- "/sys/bus/vmbus/devices/eb765408-105f-49b6-b4aa-c123b64d17d4/" #subdir
+#define FCOPY_UIO_PATH FCOPY_DEVICE_PATH(uio) +#define FCOPY_CHANNELS_PATH FCOPY_DEVICE_PATH(channels) #define FCOPY_VER_COUNT 1 static const int fcopy_versions[] = { @@ -47,9 +50,62 @@ static const int fw_versions[] = { UTIL_FW_VERSION }; -#define HV_RING_SIZE 0x4000 /* 16KB ring buffer size */ +static uint32_t get_ring_buffer_size(void) +{
- char ring_path[PATH_MAX];
- DIR *dir;
- struct dirent *entry;
- struct stat st;
- uint32_t ring_size = 0;
- int retry_count = 0;
-static unsigned char desc[HV_RING_SIZE];
- /* Find the channel directory */
- dir = opendir(FCOPY_CHANNELS_PATH);
- if (!dir) {
usleep(100 * 1000); /* Avoid race with kernel, wait 100ms and retry once */dir = opendir(FCOPY_CHANNELS_PATH);if (!dir) {syslog(LOG_ERR, "Failed to open channels directory: %s", strerror(errno));return 0;}- }
+retry_once:
- while ((entry = readdir(dir)) != NULL) {
if (entry->d_type == DT_DIR && strcmp(entry->d_name, ".") != 0 &&strcmp(entry->d_name, "..") != 0) {snprintf(ring_path, sizeof(ring_path), "%s/%s/ring",FCOPY_CHANNELS_PATH, entry->d_name);if (stat(ring_path, &st) == 0) {/** stat returns size of Tx, Rx rings combined,* so take half of it for individual ring size.*/ring_size = (uint32_t)st.st_size / 2;syslog(LOG_INFO, "Ring buffer size from %s: %u bytes",ring_path, ring_size);break;}}- }
- if (!ring_size && retry_count == 0) {
retry_count = 1;rewinddir(dir);usleep(100 * 1000); /* Wait 100ms and retry once */goto retry_once;- }
- closedir(dir);
- if (!ring_size)
syslog(LOG_ERR, "Could not determine ring size");- return ring_size;
+}
+static unsigned char *desc; static int target_fd; static char target_fname[PATH_MAX]; @@ -406,7 +462,7 @@ int main(int argc, char *argv[]) int daemonize = 1, long_index = 0, opt, ret = -EINVAL; struct vmbus_br txbr, rxbr; void *ring;
- uint32_t len = HV_RING_SIZE;
- uint32_t ring_size, len; char uio_name[NAME_MAX] = {0}; char uio_dev_path[PATH_MAX] = {0};
@@ -437,7 +493,20 @@ int main(int argc, char *argv[]) openlog("HV_UIO_FCOPY", 0, LOG_USER); syslog(LOG_INFO, "starting; pid is:%d", getpid());
- fcopy_get_first_folder(FCOPY_UIO, uio_name);
- ring_size = get_ring_buffer_size();
- if (!ring_size) {
ret = -ENODEV;goto exit;- }
- desc = malloc(ring_size * sizeof(unsigned char));
- if (!desc) {
syslog(LOG_ERR, "malloc failed for desc buffer");ret = -ENOMEM;goto exit;- }
- fcopy_get_first_folder(FCOPY_UIO_PATH, uio_name); snprintf(uio_dev_path, sizeof(uio_dev_path), "/dev/%s", uio_name); fcopy_fd = open(uio_dev_path, O_RDWR);
@@ -445,17 +514,17 @@ int main(int argc, char *argv[]) syslog(LOG_ERR, "open %s failed; error: %d %s", uio_dev_path, errno, strerror(errno)); ret = fcopy_fd;
goto exit;
goto free_desc;
- ring = vmbus_uio_map(&fcopy_fd, HV_RING_SIZE);
- ring = vmbus_uio_map(&fcopy_fd, ring_size); if (!ring) { ret = errno; syslog(LOG_ERR, "mmap ringbuffer failed; error: %d %s", ret, strerror(ret)); goto close; }
- vmbus_br_setup(&txbr, ring, HV_RING_SIZE);
- vmbus_br_setup(&rxbr, (char *)ring + HV_RING_SIZE, HV_RING_SIZE);
- vmbus_br_setup(&txbr, ring, ring_size);
- vmbus_br_setup(&rxbr, (char *)ring + ring_size, ring_size);
rxbr.vbr->imask = 0; @@ -470,7 +539,7 @@ int main(int argc, char *argv[]) continue; }
len = HV_RING_SIZE;
len = ring_size;@@ -490,6 +559,8 @@ int main(int argc, char *argv[]) } close: close(fcopy_fd); +free_desc:
- free(desc); exit: return ret; }