> -----Original Message-----
> From: Manish Honap <[email protected]>
> Sent: 01 June 2026 08:56
> To: Jonathan Cameron <[email protected]>
> Cc: Alex Williamson <[email protected]>; Shameer Kolothum Thodi
> <[email protected]>; Ankit Agrawal <[email protected]>;
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; Vikram Sethi
> <[email protected]>; Neo Jia <[email protected]>; Tarun Gupta (SW-GPU)
> <[email protected]>; Zhi Wang <[email protected]>; Krishnakant Jaju
> <[email protected]>; [email protected]; [email protected]; qemu-
> [email protected]; [email protected]; Manish Honap
> <[email protected]>
> Subject: RE: [RFC 0/9] QEMU: CXL Type-2 device passthrough via vfio-pci
>
[...]
> > > pxb-cxl bridges had no _DSM method. Without _DSM function 5 the OS
> > > defaults to treating PCI configuration as reassignable.
> >
> > That one is annoyingly controversial. I see you have Shameer's patch
> > so he can go into history of why. I tried to land that in the past and
> > I was far from the first.
>
> okay, I will check this part for additional details.
I guess the concern here is the QEMU regression reported with certain
devices with legacy IO port BARs having issues on arm64 when _DSM #5 is
specified:
https://lore.kernel.org/all/[email protected]/
For accel SMMUv3 this is fine as we restrict the devices to vfio-pci only.
One option, until there is a proper fix in the Linux kernel or EDK2, might
be to maintain a checklist so that devices known to have issues are not
attached when _DSM #5 is advertised.
Thanks,
Shameer
