[PATCH rc v7 0/7] iommu/arm-smmu-v3: Fix device crash on kdump kernel

[Jason Gunthorpe]

On Fri, Jul 03, 2026 at 11:20:34AM -0700, Nicolin Chen wrote:

> > So if you disable kdump when S2 is not supported it also disables it
> > when EL2 would be used, which effectively means it is not supported in
> > a VM.
> 
> Hmm, they are actually not exclusive: e.g. Grace has both.
> 
> EL2 is from FEAT_E2H, which is set when
>  1. IDR0.HYP=1
>  2. cpus_have_cap(ARM64_HAS_VIRT_HOST_EXTN)
> 
> VMID is from FEAT_TRANS_S2, which is set When
>  1. IDR0_S2P=1
> 
> So, host-level stage-1 TLBIs use EL2 commands (no VMID); guest-level
> TLBIs use NH_ commands (with VMID).

Oh... I see the half baked BTM stuff pushes STRW it into the NH mode
because the CPU runs in that mode so we loose the VMID :\

I guess VM support is important anyhow so you do have to scan the CD
tables and extract the ASIDs, carefully considering the STRW and VMID
of the STE :\

Jason