File 604b9070-VT-d-disable-QI-IR-before-init.patch of Package xen.23583

# Commit 04181c6fb543db01f635227c7681ced4073109ba
# Date 2021-03-12 17:01:52 +0100
# Author Igor Druzhinin <igor.druzhinin@citrix.com>
# Committer Jan Beulich <jbeulich@suse.com>
vtd: make sure QI/IR are disabled before initialisation

BIOS might pass control to Xen leaving QI and/or IR in enabled and/or
partially configured state. In case of x2APIC code path where EIM is
enabled early in boot - those are correctly disabled by Xen before any
attempt to configure. But for xAPIC that step is missing which was
proven to cause QI initialization failures on some ICX based platforms
where QI is left pre-enabled and partially configured by BIOS. That
problem becomes hard to avoid since those platforms are shipped with
x2APIC opt out being advertised by default at the same time by firmware.

Unify the behaviour between x2APIC and xAPIC code paths keeping that in
line with what Linux does.

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>

--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2159,7 +2159,7 @@ static int __must_check init_vtd_hw(void
     u32 sts;
 
     /*
-     * Basic VT-d HW init: set VT-d interrupt, clear VT-d faults.  
+     * Basic VT-d HW init: set VT-d interrupt, clear VT-d faults, etc.
      */
     for_each_drhd_unit ( drhd )
     {
@@ -2169,6 +2169,16 @@ static int __must_check init_vtd_hw(void
 
         clear_fault_bits(iommu);
 
+        /*
+         * Disable interrupt remapping and queued invalidation if
+         * already enabled by BIOS in case we've not initialized it yet.
+         */
+        if ( !x2apic_enabled )
+        {
+            disable_intremap(iommu);
+            disable_qinval(iommu);
+        }
+
         spin_lock_irqsave(&iommu->register_lock, flags);
         sts = dmar_readl(iommu->reg, DMAR_FECTL_REG);
         sts &= ~DMA_FECTL_IM;