On 30.06.2024 14:33, Jiqian Chen wrote:
> If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
> a passthrough device by using gsi, see qemu code
> xen_pt_realize->xc_physdev_map_pirq and libxl code
> pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
> will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
> is not allowed because currd is PVH dom0 and PVH has no
> X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.
>
> So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
> PHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
> And add a new check to prevent (un)map when the subject domain
> has no X86_EMU_USE_PIRQ flag.
>
> So that the interrupt of a passthrough device can be
> successfully mapped to pirq for domU with X86_EMU_USE_PIRQ flag
> when dom0 is PVH
>
> Signed-off-by: Jiqian Chen <jiqian.c...@amd.com>
> Signed-off-by: Huang Rui <ray.hu...@amd.com>
> Signed-off-by: Jiqian Chen <jiqian.c...@amd.com>
> Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
You keep carrying this R-b, despite making functional changes. This can't be
quite right.
While functionally I'm now okay with the change, I still have a code structure
concern:
> --- a/xen/arch/x86/physdev.c
> +++ b/xen/arch/x86/physdev.c
> @@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd,
> XEN_GUEST_HANDLE_PARAM(void) arg)
> if ( !d )
> break;
>
> + /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
> + if ( is_hvm_domain(d) && !has_pirq(d) )
> + {
> + rcu_unlock_domain(d);
> + return -EOPNOTSUPP;
> + }
> +
> ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
>
> rcu_unlock_domain(d);
> @@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd,
> XEN_GUEST_HANDLE_PARAM(void) arg)
> if ( !d )
> break;
>
> + /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ
> */
> + if ( is_hvm_domain(d) && !has_pirq(d) )
> + {
> + rcu_unlock_domain(d);
> + return -EOPNOTSUPP;
> + }
> +
> ret = physdev_unmap_pirq(d, unmap.pirq);
>
> rcu_unlock_domain(d);
If you did go look, you will have noticed that we use "return" in the middle
of this function only very sparingly (when alternatives would result in more
complicated code elsewhere). I think you want to avoid "return" here, too,
and probably go even further and avoid the extra rcu_unlock_domain() as well.
That's easily possible to arrange for (taking the latter case as example):
/* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
if ( !is_hvm_domain(d) || has_pirq(d) )
ret = physdev_unmap_pirq(d, unmap.pirq);
else
ret = -EOPNOTSUPP;
rcu_unlock_domain(d);
Personally I would even use a conditional operator here, but I believe
others might dislike its use in situations like this one.
The re-arrangement make a little more noticeable though that the comment
isn't quite right either: PV domains necessarily have no
X86_EMU_USE_PIRQ. Maybe "... has no notion of pIRQ"?
Jan
