[xen stable-4.13] vtd: make sure QI/IR are disabled before initialisation

[patchbot@xxxxxxx]

commit c2aaebbbc4521685bf88fb9cfff8c006fcb821af
Author:     Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
AuthorDate: Thu Mar 18 15:06:47 2021 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 18 15:06:47 2021 +0100

    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    master commit: 04181c6fb543db01f635227c7681ced4073109ba
    master date: 2021-03-12 17:01:52 +0100
---
 xen/drivers/passthrough/vtd/iommu.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 1e61e93d3f..61ba9b496b 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2118,7 +2118,7 @@ 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 )
     {
@@ -2128,6 +2128,16 @@ 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;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13