Re: [PATCH 2/2] tpm_crb: mark memory as protected

[Laurent Vivier <lvivier@redhat.com>]

Hi,

as the region is already skipped by the test of the memory region alignment, I'm going to 
update my patches by only removing the error_report() as proposed by Peter.

I will replace it by a trace to help to debug.

Thanks,
Laurent

On 7/4/23 05:07, Jason Wang wrote:
> On Thu, Jun 22, 2023 at 9:39 PM Laurent Vivier <lvivier@redhat.com> wrote:
>>
>> On 6/22/23 15:12, Peter Maydell wrote:
>>> On Tue, 20 Jun 2023 at 20:51, Laurent Vivier <lvivier@redhat.com> wrote:
>>>>
>>>> This memory is not correctly aligned and cannot be registered
>>>> by vDPA and VFIO.
>>>
>>> Isn't this a vDPA/VFIO problem? There's no requirement
>>> for RAM MemoryRegions to be aligned in any way.
> 
> It's more about the limitation of the IOMMU which can't do subpage protection.
> 
>>> Code
>>> that doesn't want to work with small or weirdly aligned
>>> regions should skip them if that's the right behaviour
>>> for that particular code IMHO.
> 
> We had already had this:
> 
>      if ((!memory_region_is_ram(section->mr) &&
>           !memory_region_is_iommu(section->mr)) ||
>          memory_region_is_protected(section->mr) ||
>          /* vhost-vDPA doesn't allow MMIO to be mapped  */
>          memory_region_is_ram_device(section->mr)) {
>          return true;
>      }
> 
>>>
>>
>> Marc-André proposed to modify vDPA code to skip the region but Michal disagreed:
>>
>> https://lists.nongnu.org/archive/html/qemu-devel/2022-11/msg03670.html
>>
>> No one wants the modification, so the problem cannot be fixed.
>>
> 
> Yes, otherwise we end up with explicit check for TPM crb in vhost code...
> 
> Thanks
> 
>> Thanks,
>> Laurent
>>
>