Re: [PATCH v2] ata: libata-core: Add BRIDGE_OK quirk for QEMU drives
From: Hannes Reinecke
Date: Thu Mar 05 2026 - 10:42:18 EST
On 3/5/26 15:53, Pedro Falcato wrote:
Currently, whenever you boot with a QEMU drive over an AHCI interface,
you get:
[ 1.632121] ata1.00: applying bridge limits
This happens due to the kernel not believing the given drive is SATA,
since word 93 of IDENTIFY (ATA_ID_HW_CONFIG) is non-zero. The result is
a pretty severe limit in max_hw_sectors_kb, which limits our IO sizes.
QEMU has set word 93 erroneously for SATA drives but does not, in any
way, emulate any of these real hardware details. There is no PATA
drive and no SATA cable.
As such, add a BRIDGE_OK quirk for QEMU HARDDISK. Special care is taken
to limit this quirk to "2.5+", to allow for fixed future versions.
This results in the max_hw_sectors being limited solely by the
controller interface's limits. Which, for AHCI controllers, takes it
from 128KB to 32767KB.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Pedro Falcato <pfalcato@xxxxxxx>
---
drivers/ata/libata-core.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index d61846f03edc..c57e35ccc092 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4231,6 +4231,7 @@ static const struct ata_dev_quirks_entry __ata_dev_quirks[] = {
/* Devices that do not need bridging limits applied */
{ "MTRON MSP-SATA*", NULL, ATA_QUIRK_BRIDGE_OK },
{ "BUFFALO HD-QSU2/R5", NULL, ATA_QUIRK_BRIDGE_OK },
+ { "QEMU HARDDISK", "2.5+", ATA_QUIRK_BRIDGE_OK },
/* Devices which aren't very happy with higher link speeds */
{ "WD My Book", NULL, ATA_QUIRK_1_5_GBPS },
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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