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Commit da20522e authored by Yanming Liu's avatar Yanming Liu Committed by Greg Kroah-Hartman
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Drivers: hv: balloon: account for vmbus packet header in max_pkt_size



[ Upstream commit 96d9d1fa ]

Commit adae1e93 ("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. hv_balloon uses
the default maximum packet size VMBUS_DEFAULT_MAX_PKT_SIZE which matches
its maximum message size, however vmbus_open expects this size to also
include vmbus packet header. This leads to 4096 bytes
dm_unballoon_request messages 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.

Allocate the buffer with HV_HYP_PAGE_SIZE more bytes to make room for
the header.

Fixes: adae1e93 ("Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer")
Suggested-by: default avatarMichael Kelley (LINUX) <mikelley@microsoft.com>
Suggested-by: default avatarAndrea Parri (Microsoft) <parri.andrea@gmail.com>
Signed-off-by: default avatarYanming Liu <yanminglr@gmail.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Reviewed-by: default avatarAndrea Parri (Microsoft) <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20220119202052.3006981-1-yanminglr@gmail.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 82cc3382
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