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

[Michal Orzel <michal.orzel@xxxxxxx>]

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.

~Michal