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Date: Mon, 10 Jan 2022 01:44:19 +0100
From: Andrea Parri <parri.andrea@...il.com>
To: Yanming Liu <yanminglr@...il.com>
Cc: linux-hyperv@...r.kernel.org, Wei Liu <wei.liu@...nel.org>,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-fbdev@...r.kernel.org, kys@...rosoft.com,
haiyangz@...rosoft.com, sthemmin@...rosoft.com,
decui@...rosoft.com, drawat.floss@...il.com, airlied@...ux.ie,
daniel@...ll.ch, mikelley@...rosoft.com, lkmlabelt@...il.com
Subject: Re: [PATCH v2] hv: account for packet descriptor in maximum packet
size
(Extending Cc: list,)
On Sun, Jan 09, 2022 at 05:55:16PM +0800, Yanming Liu wrote:
> Commit adae1e931acd ("Drivers: hv: vmbus: Copy packets sent by Hyper-V
> out of the ring buffer") introduced a notion of maximum packet size in
> vmbus channel and used that size to initialize a buffer holding all
> incoming packet along with their vmbus packet header. Currently, some
> vmbus drivers set max_pkt_size to the size of their receive buffer
> passed to vmbus_recvpacket, however vmbus_open expects this size to also
> include vmbus packet header. This leads to corruption of the ring buffer
> state when receiving a maximum sized packet.
>
> Specifically, in hv_balloon I have observed of a dm_unballoon_request
> message of 4096 bytes being truncated to 4080 bytes. When the driver
> tries to read next packet it starts from a wrong read_index, receives
> garbage and prints a lot of "Unhandled message: type: <garbage>" in
> dmesg.
>
> The same mismatch also happens in hv_fcopy, hv_kvp, hv_snapshot,
> hv_util, hyperv_drm and hyperv_fb, though bad cases are not observed
> yet.
>
> Allocate the buffer with HV_HYP_PAGE_SIZE more bytes to make room for
> the descriptor, assuming the vmbus packet header will never be larger
> than HV_HYP_PAGE_SIZE. This is essentially free compared to just adding
> 'sizeof(struct vmpacket_descriptor)' because these buffers are all more
> than HV_HYP_PAGE_SIZE bytes so kmalloc rounds them up anyway.
>
> Fixes: adae1e931acd ("Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer")
> Suggested-by: Andrea Parri (Microsoft) <parri.andrea@...il.com>
> Signed-off-by: Yanming Liu <yanminglr@...il.com>
Thanks for sorting this out; the patch looks good to me:
Reviewed-by: Andrea Parri (Microsoft) <parri.andrea@...il.com>
In future submissions (if any), please include LKML as well as subsystem
lists&maintainers; scripts/get_maintainer.pl can be useful to this end.
Andrea
> ---
> v2: Changed to modify max_pkt_size in individual drivers instead of in
> vmbus code as suggested by Andrea Parri.
>
> drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 2 ++
> drivers/hv/hv_balloon.c | 7 +++++++
> drivers/hv/hv_fcopy.c | 2 +-
> drivers/hv/hv_kvp.c | 2 +-
> drivers/hv/hv_snapshot.c | 2 +-
> drivers/hv/hv_util.c | 17 +++++++++++++++++
> drivers/video/fbdev/hyperv_fb.c | 2 ++
> 7 files changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> index c0155c6271bf..bf1548054276 100644
> --- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> +++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> @@ -478,6 +478,8 @@ int hyperv_connect_vsp(struct hv_device *hdev)
> struct drm_device *dev = &hv->dev;
> int ret;
>
> + hdev->channel->max_pkt_size = HV_HYP_PAGE_SIZE + VMBUS_MAX_PACKET_SIZE;
> +
> ret = vmbus_open(hdev->channel, VMBUS_RING_BUFSIZE, VMBUS_RING_BUFSIZE,
> NULL, 0, hyperv_receive, hdev);
> if (ret) {
> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
> index ca873a3b98db..ee2527c3d3b8 100644
> --- a/drivers/hv/hv_balloon.c
> +++ b/drivers/hv/hv_balloon.c
> @@ -1660,6 +1660,13 @@ static int balloon_connect_vsp(struct hv_device *dev)
> unsigned long t;
> int ret;
>
> + /*
> + * max_pkt_size should be large enough for one vmbus packet header plus
> + * our receive buffer size. We assume vmbus packet header is smaller
> + * than HV_HYP_PAGE_SIZE.
> + */
> + dev->channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
> +
> ret = vmbus_open(dev->channel, dm_ring_size, dm_ring_size, NULL, 0,
> balloon_onchannelcallback, dev);
> if (ret)
> diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
> index 660036da7449..07a508ce65db 100644
> --- a/drivers/hv/hv_fcopy.c
> +++ b/drivers/hv/hv_fcopy.c
> @@ -349,7 +349,7 @@ int hv_fcopy_init(struct hv_util_service *srv)
> {
> recv_buffer = srv->recv_buffer;
> fcopy_transaction.recv_channel = srv->channel;
> - fcopy_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
> + fcopy_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 3;
>
> /*
> * When this driver loads, the user level daemon that
> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> index c698592b83e4..b85d725ae5b1 100644
> --- a/drivers/hv/hv_kvp.c
> +++ b/drivers/hv/hv_kvp.c
> @@ -757,7 +757,7 @@ hv_kvp_init(struct hv_util_service *srv)
> {
> recv_buffer = srv->recv_buffer;
> kvp_transaction.recv_channel = srv->channel;
> - kvp_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 4;
> + kvp_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 5;
>
> /*
> * When this driver loads, the user level daemon that
> diff --git a/drivers/hv/hv_snapshot.c b/drivers/hv/hv_snapshot.c
> index 6018b9d1b1fb..dba6baacbf17 100644
> --- a/drivers/hv/hv_snapshot.c
> +++ b/drivers/hv/hv_snapshot.c
> @@ -375,7 +375,7 @@ 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 = HV_HYP_PAGE_SIZE * 3;
>
> /*
> * When this driver loads, the user level daemon that
> diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
> index 835e6039c186..a7b88c067c07 100644
> --- a/drivers/hv/hv_util.c
> +++ b/drivers/hv/hv_util.c
> @@ -112,6 +112,8 @@ static int hv_shutdown_init(struct hv_util_service *srv)
>
> hibernation_supported = hv_is_hibernation_supported();
>
> + channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
> +
> return 0;
> }
>
> @@ -133,9 +135,11 @@ static struct hv_util_service util_timesynch = {
> .util_deinit = hv_timesync_deinit,
> };
>
> +static int heartbeat_init(struct hv_util_service *src);
> static void heartbeat_onchannelcallback(void *context);
> static struct hv_util_service util_heartbeat = {
> .util_cb = heartbeat_onchannelcallback,
> + .util_init = heartbeat_init,
> };
>
> static struct hv_util_service util_kvp = {
> @@ -553,6 +557,15 @@ static void heartbeat_onchannelcallback(void *context)
> }
> }
>
> +static int heartbeat_init(struct hv_util_service *srv)
> +{
> + struct vmbus_channel *channel = srv->channel;
> +
> + channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
> +
> + return 0;
> +}
> +
> #define HV_UTIL_RING_SEND_SIZE VMBUS_RING_SIZE(3 * HV_HYP_PAGE_SIZE)
> #define HV_UTIL_RING_RECV_SIZE VMBUS_RING_SIZE(3 * HV_HYP_PAGE_SIZE)
>
> @@ -734,6 +747,8 @@ static struct ptp_clock *hv_ptp_clock;
>
> static int hv_timesync_init(struct hv_util_service *srv)
> {
> + struct vmbus_channel *channel = srv->channel;
> +
> spin_lock_init(&host_ts.lock);
>
> INIT_WORK(&adj_time_work, hv_set_host_time);
> @@ -750,6 +765,8 @@ static int hv_timesync_init(struct hv_util_service *srv)
> hv_ptp_clock = NULL;
> }
>
> + channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
> +
> return 0;
> }
>
> diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
> index 23999df52739..ae4240777f7d 100644
> --- a/drivers/video/fbdev/hyperv_fb.c
> +++ b/drivers/video/fbdev/hyperv_fb.c
> @@ -636,6 +636,8 @@ static int synthvid_connect_vsp(struct hv_device *hdev)
> struct hvfb_par *par = info->par;
> int ret;
>
> + hdev->channel->max_pkt_size = HV_HYP_PAGE_SIZE + MAX_VMBUS_PKT_SIZE;
> +
> ret = vmbus_open(hdev->channel, RING_BUFSIZE, RING_BUFSIZE,
> NULL, 0, synthvid_receive, hdev);
> if (ret) {
> --
> 2.34.1
>
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