On 28.02.2025 12:32, Roger Pau Monne wrote:
> @@ -191,8 +193,6 @@ void msi_compose_msg(unsigned vector, const cpumask_t
> *cpu_mask, struct msi_msg
>
> static int write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
> {
> - entry->msg = *msg;
> -
> if ( iommu_intremap != iommu_intremap_off )
> {
> int rc;
> @@ -203,6 +203,20 @@ static int write_msi_msg(struct msi_desc *entry, struct
> msi_msg *msg)
> return rc;
> }
>
> + /*
> + * Avoid updating the MSI entry if the address and data fields haven't
> + * changed. When using interrupt remapping changing the MSI affinity
> + * shouldn't change the interrupt remapping table index, and hence the
> MSI
> + * address and data fields should remain the same.
> + */
> + if ( entry->msg.address == msg->address && entry->msg.data == msg->data )
> + {
> + entry->msg.dest32 = msg->dest32;
> + return 0;
> + }
> +
> + entry->msg = *msg;
It is perhaps pure luck that iommu_update_ire_from_msi() doesn't use entry's
"msg" field, and hence that this re-arrangement is okay. It's unclear to me
whether going forward this might not bite us.
> @@ -1407,7 +1415,9 @@ int pci_restore_msi_state(struct pci_dev *pdev)
> }
> type = entry->msi_attrib.type;
>
> - msg = entry->msg;
> + msg.dest32 = entry->msg.dest32;
> + msi_compose_msg(desc->arch.vector, NULL, &msg);
> + entry->msg = (typeof(entry->msg)){};
> write_msi_msg(entry, &msg);
Hmm, this isn't exactly a "restore" then anymore. That said, re-constructing
the message may even be more correct. Then, however, the question is whether
passing NULL as msi_compose_msg()'s middle argument is really appropriate. A
little bit of commentary may be desirable here in any event, also as to need
to clear entry->msg.
There's (at least) one place where behavior changes with the change of what
we store in struct msi_desc's msg field (previously untranslated, now
translated): dump_msi() wants to use the untranslated form. I fear it can't
even re-construct some of the data it means to log (without reading from
the IRTE).
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -1182,7 +1182,7 @@ static void cf_check dma_msi_end(struct irq_desc *desc,
> u8 vector)
> static void cf_check dma_msi_set_affinity(
> struct irq_desc *desc, const cpumask_t *mask)
> {
> - struct msi_msg msg;
> + struct msi_msg msg = {};
> unsigned int dest;
> unsigned long flags;
> struct vtd_iommu *iommu = desc->action->dev_id;
Why not a similar transformation as you do in set_msi_affinity(), eliminating
the local "dest"?
A change like the one here is likely needed in __hpet_setup_msi_irq(), to
prevent accidental "uninitialized struct field" warnings.
hpet_msi_set_affinity() might then also want to use msi_compose_msg(), albeit
that may also be regarded as an independent change.
Jan
