x86/msi: always propagate MSI writes when not in active system mode

Relax the limitation on MSI register writes, and only apply it when the
system is in active state.  For example AMD IOMMU drivers rely on using
set_msi_affinity() to force an MSI register write on resume from
suspension.

The original patch intention was to reduce the number of MSI register
writes when the system is in active state.  Leave the other states to
always perform the writes, as it's safer given the existing code, and it's
expected to not make a difference performance wise.

For such propagation to work even when the IRT index is not updated the MSI
message must be adjusted in all success cases for AMD IOMMU, not just when
the index has been newly allocated.

Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Fixes: 8e60d47cf011 ('x86/iommu: avoid MSI address and data writes if IRT index hasn't changed')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index 163ccf8747206dbbf995b2c2be91b54362415e29..8bb3bb18af6198f236d2dda06ccd410e313f3c04 100644 (file)
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -189,6 +189,15 @@ static int write_msi_msg(struct msi_desc *entry, struct msi_msg *msg,
 {
     entry->msg = *msg;
 
+    if ( unlikely(system_state != SYS_STATE_active) )
+        /*
+         * Always propagate writes when not in the 'active' state.  The
+         * optimization to avoid the MSI address and data registers write is
+         * only relevant for runtime state, and drivers on resume (at least)
+         * rely on set_msi_affinity() to update the hardware state.
+         */
+        force = true;
+
     if ( iommu_intremap != iommu_intremap_off )
     {
         int rc;

diff --git a/xen/drivers/passthrough/amd/iommu_intr.c b/xen/drivers/passthrough/amd/iommu_intr.c
index 9abdc38053d70fc184a2584930e9cc1ee2530d45..08766122b4219a1daa4847a984f0e49ad66e91db 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_intr.c
+++ b/xen/drivers/passthrough/amd/iommu_intr.c
@@ -546,7 +546,7 @@ int cf_check amd_iommu_msi_msg_update_ire(
     rc = update_intremap_entry_from_msi_msg(iommu, bdf, nr,
                                             &msi_desc->remap_index,
                                             msg, &data);
-    if ( rc > 0 )
+    if ( rc >= 0 )
     {
         for ( i = 1; i < nr; ++i )
             msi_desc[i].remap_index = msi_desc->remap_index + i;