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Re: [Qemu-devel] [PATCH v2 3/3] ahci-test: test atapi read_cd with bcl,

From: John Snow
Subject: Re: [Qemu-devel] [PATCH v2 3/3] ahci-test: test atapi read_cd with bcl, nb_sectors = 0
Date: Wed, 2 Nov 2016 11:01:33 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 11/02/2016 09:33 AM, Kevin Wolf wrote:
Am 01.11.2016 um 04:16 hat John Snow geschrieben:
Commit 9ef2e93f introduced the concept of tagging ATAPI commands as
NONDATA, but this introduced a regression for certain commands better
described as CONDDATA. read_cd is such a command that both requires
a non-zero BCL if a transfer size is set, but is perfectly content to
accept a zero BCL if the transfer size is 0.

This test adds a regression test for the case where BCL and nb_sectors
are both 0.

Flesh out the CDROM tests by:

(1) Allowing the test to specify a BCL
(2) Allowing the buffer comparison test to compare a 0-size buffer
(3) Fix the BCL specification in libqos (It is LE, not BE)
(4) Add a nice human-readable message for future SCSI command additions

Signed-off-by: John Snow <address@hidden>

diff --git a/tests/libqos/ahci.c b/tests/libqos/ahci.c
index 5180d65..15fa888 100644
--- a/tests/libqos/ahci.c
+++ b/tests/libqos/ahci.c
@@ -864,16 +865,12 @@ AHCICommand *ahci_command_create(uint8_t command_name)
     return cmd;

-AHCICommand *ahci_atapi_command_create(uint8_t scsi_cmd)
+AHCICommand *ahci_atapi_command_create(uint8_t scsi_cmd, uint16_t bcl)
     AHCICommand *cmd = ahci_command_create(CMD_PACKET);
     cmd->atapi_cmd = g_malloc0(16);
     cmd->atapi_cmd[0] = scsi_cmd;
-    /* ATAPI needs a PIO transfer chunk size set inside of the LBA registers.
-     * The block/sector size is a natural default. */
-    cmd->fis.lba_lo[1] = ATAPI_SECTOR_SIZE >> 8 & 0xFF;
-    cmd->fis.lba_lo[2] = ATAPI_SECTOR_SIZE & 0xFF;
+    stw_le_p(&cmd->fis.lba_lo[1], bcl);
     return cmd;

If I'm not mistaken, you're changing the endianness here, which seems
to be a silent bug fix.

For some reason the test passes both ways. Does the actual value even
matter with AHCI, as long as it's non-zero? Do we end up with the same
result with BCL=0x0200 and BCL=0x0002, just that we split it into some
more iterations for the latter (or deeper recursion, actually)?


Well, not silent, I did mention it in the cover letter. Your analysis of the mistake is correct. One way is just simply more iterations.


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