Re: [PATCH v3] xen/arm: pci: fix check in pci_check_bar()

[Julien Grall <julien@xxxxxxx>]

On 13/07/2023 19:18, Julien Grall wrote:
> On 12/07/2023 18:04, Rahul Singh wrote:
> > Hi Stewart,
> >
> > > On 12 Jul 2023, at 2:52 pm, Stewart Hildebrand 
> > > <Stewart.Hildebrand@xxxxxxx> wrote:
> > > When mapping BARs for vPCI, it's valid for a BAR mfn_t start to equal 
> > > the BAR
> > > mfn_t end (i.e. start == end) since end is inclusive. However, 
> > > pci_check_bar()
> > > currently returns false in this case, which results in Xen not 
> > > mapping the BAR
> > > in the guest 2nd stage page tables. In this example boot log, Linux 
> > > has mapped
> > > the BARs in the 1st stage, but since Xen did not map them in the 2nd 
> > > stage,
> > > Linux encounters a data abort and panics:
> > >
> > > [    2.593300] pci 0000:00:00.0: BAR 0: assigned [mem 
> > > 0x50008000-0x50008fff]
> > > [    2.593682] pci 0000:00:00.0: BAR 2: assigned [mem 
> > > 0x50009000-0x50009fff]
> > > [    2.594066] pci 0000:00:00.0: BAR 4: assigned [mem 
> > > 0x5000a000-0x5000afff]
> > > ...
> > > [    2.810502] virtio-pci 0000:00:00.0: enabling device (0000 -> 0002)
> > > (XEN) 0000:00:00.0: not mapping BAR [50008, 50008] invalid position
> > > (XEN) 0000:00:00.0: not mapping BAR [50009, 50009] invalid position
> > > (XEN) 0000:00:00.0: not mapping BAR [5000a, 5000a] invalid position
> > > [    2.817502] virtio-pci 0000:00:00.0: virtio_pci: leaving for 
> > > legacy driver
> > > [    2.817853] virtio-pci 0000:00:00.0: enabling bus mastering
> > > (XEN) arch/arm/traps.c:1992:d0v0 HSR=0x00000093010045 
> > > pc=0xffff8000089507d4 gva=0xffff80000c46d012 gpa=0x00000050008012
> > > [    2.818397] Unable to handle kernel ttbr address size fault at 
> > > virtual address ffff80000c46d012
> > > ...
> > >
> > > Adjust the end physical address e to account for the full page when 
> > > converting
> > > from mfn, at which point s and e cannot be equal, so drop the 
> > > equality check in
> > > the condition.
> > >
> > > Note that adjusting e to account for the full page also increases the 
> > > accuracy
> > > of the subsequent is_bar_valid check.
> > >
> > > Fixes: cc80e2bab0d0 ("xen/pci: replace call to is_memory_hole to 
> > > pci_check_bar")
> > > Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> > > Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > I tested the patch on N1SDP board everything works.
> >
> > Reviewed-by: Rahul Singh <rahul.singh@xxxxxxx>
> > Tested-by: Rahul Singh <rahul.singh@xxxxxxx>
> Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
And committed.

Cheers,

--
Julien Grall