diff options
| author |   Michael Kelley <mikelley@microsoft.com> | 2022-02-09 08:11:10 -0800 |
|---|---|---|
| committer |   Wei Liu <wei.liu@kernel.org> | 2022-02-18 13:08:18 +0000 |
| commit | 6de74d1069b821e96460d0fc2edfc35785db04fb (patch) | |
| tree | 7670a968e8a04d89202a732790a580e2a7f41a8c | |
| parent | Drivers: hv: Compare cpumasks and not their weights in init_vp_index() (diff) | |
| download | linux-dev-6de74d1069b821e96460d0fc2edfc35785db04fb.tar.xz linux-dev-6de74d1069b821e96460d0fc2edfc35785db04fb.zip | |
hv_utils: Add comment about max VMbus packet size in VSS driver
The VSS driver allocates a VMbus receive buffer significantly
larger than sizeof(hv_vss_msg), with no explanation. To help
prevent future mistakes, add a #define and comment about why
this is done.
No functional change.
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1644423070-75125-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
| -rw-r--r-- | drivers/hv/hv_snapshot.c | 7 | ||||
| -rw-r--r-- | include/uapi/linux/hyperv.h | 11 |
2 files changed, 16 insertions, 2 deletions
diff --git a/drivers/hv/hv_snapshot.c b/drivers/hv/hv_snapshot.c index 6018b9d1b1fb..0d2184be1691 100644 --- a/drivers/hv/hv_snapshot.c +++ b/drivers/hv/hv_snapshot.c @@ -31,6 +31,9 @@ static const int fw_versions[] = { UTIL_FW_VERSION }; +/* See comment with struct hv_vss_msg regarding the max VMbus packet size */ +#define VSS_MAX_PKT_SIZE (HV_HYP_PAGE_SIZE * 2) + /* * Timeout values are based on expecations from host */ @@ -298,7 +301,7 @@ void hv_vss_onchannelcallback(void *context) if (vss_transaction.state > HVUTIL_READY) return; - if (vmbus_recvpacket(channel, recv_buffer, HV_HYP_PAGE_SIZE * 2, &recvlen, &requestid)) { + if (vmbus_recvpacket(channel, recv_buffer, VSS_MAX_PKT_SIZE, &recvlen, &requestid)) { pr_err_ratelimited("VSS request received. Could not read into recv buf\n"); return; } @@ -375,7 +378,7 @@ hv_vss_init(struct hv_util_service *srv) } recv_buffer = srv->recv_buffer; vss_transaction.recv_channel = srv->channel; - vss_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2; + vss_transaction.recv_channel->max_pkt_size = VSS_MAX_PKT_SIZE; /* * When this driver loads, the user level daemon that diff --git a/include/uapi/linux/hyperv.h b/include/uapi/linux/hyperv.h index daf82a230c0e..aaa502a7bff4 100644 --- a/include/uapi/linux/hyperv.h +++ b/include/uapi/linux/hyperv.h @@ -90,6 +90,17 @@ struct hv_vss_check_dm_info { __u32 flags; } __attribute__((packed)); +/* + * struct hv_vss_msg encodes the fields that the Linux VSS + * driver accesses. However, FREEZE messages from Hyper-V contain + * additional LUN information that Linux doesn't use and are not + * represented in struct hv_vss_msg. A received FREEZE message may + * be as large as 6,260 bytes, so the driver must allocate at least + * that much space, not sizeof(struct hv_vss_msg). Other messages + * such as AUTO_RECOVER may be as large as 12,500 bytes. However, + * because the Linux VSS driver responds that it doesn't support + * auto-recovery, it should not receive such messages. + */ struct hv_vss_msg { union { struct hv_vss_hdr vss_hdr; |