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

[Peter Maydell]

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. 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.

> An error is reported for vhost-vdpa case:
> qemu-kvm: vhost_vdpa_listener_region_add received unaligned region
>
> To make it ignored by VFIO and vDPA devices, mark it as RAM_PROTECTED.
>
> The RAM_PROTECTED flag has been introduced to skip memory
> region that looks like RAM but is not accessible via normal
> mechanims, including DMA.

You can DMA to a small RAM region if you want to...

thanks
-- PMM