[PATCH for-4.15] vtd: make sure QI/IR are disabled before initialisation

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

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.

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>
---
 xen/arch/x86/apic.c                 |  2 +-
 xen/drivers/passthrough/vtd/iommu.c | 12 +++++++++++-
 xen/include/asm-x86/apic.h          |  1 +
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/apic.c b/xen/arch/x86/apic.c
index 7497ddb..8ab8214 100644
--- a/xen/arch/x86/apic.c
+++ b/xen/arch/x86/apic.c
@@ -47,7 +47,7 @@ static bool __read_mostly tdt_enabled;
 static bool __initdata tdt_enable = true;
 boolean_param("tdt", tdt_enable);
 
-static bool __read_mostly iommu_x2apic_enabled;
+bool __read_mostly iommu_x2apic_enabled;
 
 static struct {
     int active;
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index d136fe3..4aa7a31 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2080,7 +2080,7 @@ 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 )
     {
@@ -2090,6 +2090,16 @@ 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 ( !iommu_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;
diff --git a/xen/include/asm-x86/apic.h b/xen/include/asm-x86/apic.h
index 8ddb896..2fe54bb 100644
--- a/xen/include/asm-x86/apic.h
+++ b/xen/include/asm-x86/apic.h
@@ -24,6 +24,7 @@ enum apic_mode {
     APIC_MODE_X2APIC    /* x2APIC mode - common for large MP machines */
 };
 
+extern bool iommu_x2apic_enabled;
 extern u8 apic_verbosity;
 extern bool directed_eoi_enabled;
 
-- 
2.7.4