Re: [PATCH for-4.21 v2] vpci/msix: improve handling of bogus MSI-X capabilities

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Oct 08, 2025 at 09:17:30AM -0400, Stewart Hildebrand wrote:
> On 10/8/25 10:39, Roger Pau Monne wrote:
> > I've had the luck to come across a PCI card that exposes a MSI-X capability
> > where the BIR of the vector and PBA tables points at a BAR that has 0 size.
> > 
> > This doesn't play nice with the code in vpci_make_msix_hole(), as it would
> > still use the address of such empty BAR (0) and attempt to carve a hole in
> > the p2m.  This leads to errors like the one below being reported by Xen:
> > 
> > d0v0 0000:22:00.0: existing mapping (mfn: 181c4300 type: 0) at 0 clobbers 
> > MSIX MMIO area
> > 
> > And the device left unable to enable memory decoding due to the failure
> > reported by vpci_make_msix_hole().
> > 
> > Introduce checking in init_msix() to ensure the BARs containing the MSI-X
> > tables are usable.  This requires checking that the BIR points to a
> > non-empty BAR, and the offset and size of the MSI-X tables can fit in the
> > target BAR.
> > 
> > This fixes booting PVH dom0 on Supermicro AS -2126HS-TN severs with AMD
> > EPYC 9965 processors.  The broken device is:
> > 
> > 22:00.0 SATA controller: Advanced Micro Devices, Inc. [AMD] FCH SATA 
> > Controller [AHCI mode] (rev 93)
> > 
> > There are multiple of those integrated controllers in the system, all
> > broken in the same way.
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > Released-Acked-By: Oleksii Kurochko<oleksii.kurochko@xxxxxxxxx>
> > ---
> > Cc: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> > Cc: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> > ---
> > Changes since v1:
> >  - Introduce a DEVICE BUG prefix.
> >  - Remove extra newline.
> >  - Fix typo in commit message.
> > ---
> >  xen/drivers/vpci/msix.c | 50 ++++++++++++++++++++++++++++++++++++-----
> >  xen/include/xen/lib.h   |  3 +++
> >  2 files changed, 48 insertions(+), 5 deletions(-)
> > 
> > diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
> > index 54a5070733aa..4ddcefbcb274 100644
> > --- a/xen/drivers/vpci/msix.c
> > +++ b/xen/drivers/vpci/msix.c
> 
> Do we need to #include <xen/lib.h>?

Can do, it's the same header that has the declarations for the printk
functions that we already use in msix.c, so if it wasn't indirectly
included the file won't build already.

Thanks, Roger.