Re: [PATCH] vhost-vdpa: skip TPM CRB memory section

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 2599 bytes --]

Hi

On Wed, Nov 23, 2022 at 12:32 AM Michael S. Tsirkin <mst@redhat.com> wrote:

> On Tue, Nov 22, 2022 at 06:53:49PM +0400, marcandre.lureau@redhat.com
> wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > 851d6d1a0f ("vfio/common: remove spurious tpm-crb-cmd misalignment
> > warning") removed the warning on vfio_listener_region_add() path.
> >
> > An error is reported for vhost-vdpa case:
> > qemu-kvm: vhost_vdpa_listener_region_add received unaligned region
> >
> > Skip the CRB device.
> >
> > Fixes:
> > https://bugzilla.redhat.com/show_bug.cgi?id=2141965
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> >  hw/virtio/vhost-vdpa.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index 7468e44b87..9d7206e4b8 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -19,6 +19,7 @@
> >  #include "hw/virtio/virtio-net.h"
> >  #include "hw/virtio/vhost-shadow-virtqueue.h"
> >  #include "hw/virtio/vhost-vdpa.h"
> > +#include "sysemu/tpm.h"
> >  #include "exec/address-spaces.h"
> >  #include "migration/blocker.h"
> >  #include "qemu/cutils.h"
> > @@ -46,6 +47,11 @@ static bool
> vhost_vdpa_listener_skipped_section(MemoryRegionSection *section,
> >  {
> >      Int128 llend;
> >
> > +    if (TPM_IS_CRB(section->mr->owner)) {
> > +        /* The CRB command buffer has its base address unaligned. */
> > +        return true;
> > +    }
> > +
>
> Quite a hack. We can't really keep adding dependency on random devices
>

Agree it's not great. but it's not strictly a dependency. At least you can
still build with !CONFIG_TPM.

to vhost. And would you add hacks like this to listeners?
> Pls figure out what's special about this buffer.
> Also if this section is unaligned then doesn't it break up
> other aligned sections?
>

See the original discussion:
https://patchew.org/QEMU/20220208133842.112017-1-eric.auger@redhat.com/20220208133842.112017-2-eric.auger@redhat.com/

It is not clear whether aligning the tpm-crb-cmd region would work
(overlapping tpm-crb-mmio).

Peter Maydell said: "There's nothing that guarantees alignment for memory
regions at all, whether they're RAM, IO or anything else.".

Maybe vfio/vhost should simply skip those odd regions silently.



>
> >      if ((!memory_region_is_ram(section->mr) &&
> >           !memory_region_is_iommu(section->mr)) ||
> >          memory_region_is_protected(section->mr) ||
> > --
> > 2.38.1
>
>

[-- Attachment #2: Type: text/html, Size: 4190 bytes --]