Re: [PATCH v3 1/4] xen/arm/static-shmem: Static-shmem should be direct-mapped for direct-mapped domains

[Henry Wang <xin.wang2@xxxxxxx>]

Hi Michal,

On 5/20/2024 11:46 PM, Michal Orzel wrote:
> Hi Henry,
>
> On 20/05/2024 16:52, Henry Wang wrote:
> > Hi Michal, Luca,
> >
> > On 5/20/2024 7:24 PM, Michal Orzel wrote:
> > > Hi Henry,
> > >
> > > +CC: Luca
> > >
> > > On 17/05/2024 05:21, Henry Wang wrote:
> > > > To make things easier, add restriction that static shared memory
> > > > should also be direct-mapped for direct-mapped domains. Check the
> > > > host physical address to be matched with guest physical address when
> > > > parsing the device tree. Document this restriction in the doc.
> > > I'm ok with this restriction.
> > >
> > > @Luca, do you have any use case preventing us from making this restriction?
> > >
> > > This patch clashes with Luca series so depending on which goes first,
> > I agree that there will be some conflicts between the two series. To
> > avoid back and forth, if Luca's series goes in first, would it be ok for
> > you if I place the same check from this patch in
> > handle_shared_mem_bank() like below?
> >
> > diff --git a/xen/arch/arm/static-shmem.c b/xen/arch/arm/static-shmem.c
> > index 9c3a83042d..2d23fa4917 100644
> > --- a/xen/arch/arm/static-shmem.c
> > +++ b/xen/arch/arm/static-shmem.c
> > @@ -219,6 +219,13 @@ static int __init handle_shared_mem_bank(struct
> > domain *d, paddr_t gbase,
> >        pbase = shm_bank->start;
> >        psize = shm_bank->size;
> >
> > +    if ( is_domain_direct_mapped(d) && (pbase != gbase) )
> > +    {
> > +        printk("%pd: physical address 0x%"PRIpaddr" and guest address
> > 0x%"PRIpaddr" are not direct-mapped.\n",
> > +               d, pbase, gbase);
> > +        return -EINVAL;
> > +    }
> > +
> >        printk("%pd: SHMEM map from %s: mphys 0x%"PRIpaddr" -> gphys
> > 0x%"PRIpaddr", size 0x%"PRIpaddr"\n",
> >               d, bank_from_heap ? "Xen heap" : "Host", pbase, gbase, psize);
> >
> > > Acked-by: Michal Orzel <michal.orzel@xxxxxxx>
> > Thanks. I will take the tag if you are ok with above diff (for the case
> > if this series goes in later than Luca's).
> I would move this check to process_shm() right after "gbase = dt_read_paddr" 
> setting.
> This would be the most natural placement for such a check.
That sounds good. Thanks! IIUC we only need to add the check for the 
pbase != INVALID_PADDR case correct?
Kind regards,
Henry

> ~Michal