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

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

On 10/9/25 03:23, Roger Pau Monné wrote:
> 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

s/severs/servers/

>>> 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,

With that adjusted:
Reviewed-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>

> 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.