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, 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).
> >           }
> > +        if ( is_domain_direct_mapped(d) && (pbase != gbase) )
> > +        {
> > +            printk("%pd: physical address 0x%"PRIpaddr" and guest address 
> > 0x%"PRIpaddr" are not 1:1 direct-mapped.\n",
> NIT: 1:1 and direct-mapped means the same so no need to place them next to each 
> other
Ok. I will drop the "1:1" in the next version. Thanks.

Kind regards,
Henry

> ~Michal