Re: [PATCH] ata: ahci: force 32-bit DMA for ASMedia ASM1166

[David Laight]

On Mon, 22 Jun 2026 20:31:54 +0900
Damien Le Moal <dlemoal@xxxxxxxxxx> wrote:

> On 6/21/26 19:08, Alvin Lim wrote:
> > The ASMedia ASM1166 SATA controller (1b21:1166) advertises 64-bit DMA
> > support (AHCI CAP.S64A), but on systems with the IOMMU enabled - where it
> > can be handed DMA addresses above 4 GB - it silently corrupts data in
> > transit. Reads return different, wrong data on each access. SMART is clean,
> > there are no SATA link resets and no MCE is raised, so the corruption is
> > invisible until it surfaces as filesystem metadata errors (XFS EUCLEAN)
> > or, on Ceph, mass scrub errors across multiple independent filesystems at
> > once - i.e. host-level, not filesystem-level.
> > 
> > This is the same failure mode already quirked for other controllers that
> > falsely claim working 64-bit DMA. See commit 105c42566a55 ("ata: ahci:
> > force 32-bit DMA for JMicron JMB582/JMB585") and commit 20730e9b2778
> > ("ahci: add 43-bit DMA address quirk for ASMedia ASM1061 controllers").
> > The ASM1166 currently maps to plain board_ahci with no DMA limit.  
> 
> Have you tried the same quirk, limiting DMA to 43-bits ? It is very likely that
> this adapter bug is the same as the 1061.
> 

It would also be worth checking that you get the read fails with a 44-bit mask.

I'd guess it also requires that you keep the controller busy for (about) 8TB
of reads - which is where sequential address allocation would exceed 43-bits.
But that is just conjecture since I've not looked at the iommu code.

	David