linux-kernel - [PATCH 2/4] scsi: ufshpb: Use a correct max multi chunk

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Date:   Sun,  8 Aug 2021 12:00:22 +0300
From:   Avri Altman <avri.altman@....com>
To:     "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bart Van Assche <bvanassche@....org>,
        Daejun Park <daejun7.park@...sung.com>,
        Avri Altman <avri.altman@....com>
Subject: [PATCH 2/4] scsi: ufshpb: Use a correct max multi chunk

In HPB2.0, if pre_req_min_tr_len < transfer_len < pre_req_max_tr_len
the driver is expected to send a HPB-WRITE-BUFFER companion to HPB-READ.

The upper bound should fit into a single byte, regardless of
bMAX_ DATA_SIZE_FOR_HPB_SINGLE_CMD which being an attribute (u32) can
be significantly larger.

To further illustrate the issue let us consider the following scenario:
 - SCSI_DEFAULT_MAX_SECTORS is 1024 limiting the IO chunks to 512KB
 - The OEM changes scsi_host_template .max_sectors to be 2048, which
   allows a 1M requests: transfer_len = 256
 - pre_req_max_tr_len = HPB_MULTI_CHUNK_HIGH = 256
 - ufshpb_is_supported_chunk returns true (256 <= 256)
 - WARN_ON_ONCE(256 > 256) doesn't warn
 - ufshpb_set_hpb_read_to_upiu cast transfer_len to u8: transfer_len = 0
 - the command is failing with illegal request

Fixes: 41d8a9333cc9 (scsi: ufs: ufshpb: Add HPB 2.0 support)
Signed-off-by: Avri Altman <avri.altman@....com>
---
 drivers/scsi/ufs/ufshpb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
index c74a6c35a446..6df317dfe034 100644
--- a/drivers/scsi/ufs/ufshpb.h
+++ b/drivers/scsi/ufs/ufshpb.h
@@ -32,7 +32,7 @@
 /* hpb support chunk size */
 #define HPB_LEGACY_CHUNK_HIGH			1
 #define HPB_MULTI_CHUNK_LOW			7
-#define HPB_MULTI_CHUNK_HIGH			256
+#define HPB_MULTI_CHUNK_HIGH			255
 
 /* hpb vender defined opcode */
 #define UFSHPB_READ				0xF8
-- 
2.17.1