Re: [PATCH] ahci: force 32-bit DMA for JMicron JMB582/JMB585

[Niklas Cassel <cassel@kernel.org>]

On Thu, Apr 02, 2026 at 10:04:18PM -0700, Arthur Husband wrote:
> The JMicron JMB585 (and JMB582) SATA controllers advertise 64-bit DMA
> support via the S64A bit in the AHCI CAP register, but their 64-bit DMA
> implementation is defective. Under sustained I/O, DMA transfers targeting
> addresses above 4GB silently corrupt data — writes land at incorrect
> memory addresses with no errors logged.
> 
> This has been confirmed on multiple platforms (Minisforum N5 Pro,
> Raspberry Pi, Unraid, Proxmox, TrueNAS) and is consistent with the
> controller truncating or mishandling upper address bits during 64-bit
> DMA transactions.

This does not make sense to me (probably because it is AI generated).

What is a platform here? Rasperry Pi is a SBC, TrueNAS is a Linux distro
based on Debian.

I would just drop this whole paragraph.


> 
> The failure pattern is identical to the ASMedia ASM1062 (commit
> edb96a15dc18), which also falsely advertised 64-bit DMA and was fixed
> with AHCI_HFLAG_32BIT_ONLY.

Please use the normal kernel style to reference commits, i.e.:
"commit '12 character SHA1' (description)"

git --no-pager show -s --abbrev-commit --abbrev=12 --pretty=format:"%h (\"%s\")%n"

Also, the SHA1 you are referencing does not exist in mainline.

Most likely you are thinking of:
commit 20730e9b2778 ("ahci: add 43-bit DMA address quirk for ASMedia
ASM1061 controllers")

However, this commit uses flag AHCI_HFLAG_43BIT_ONLY
(and not AHCI_HFLAG_32BIT_ONLY as claimed by AI).


> 
> On the Minisforum N5 Pro specifically, the combination of the JMB585's
> broken 64-bit DMA with the AMD Family 1Ah (Strix Point) IOMMU causes
> silent data corruption that is only detectable via checksumming
> filesystems (BTRFS/ZFS scrub). The corruption occurs when 32-bit IOVA

We don't usually mention out of tree filesystems (ZFS) in our commit logs.


Thank you for the patch!


Kind regards,
Niklas