iommu/vt-d: Use cmpxchg16b to update posted format IRTE atomically
If IRTE is in posted format, the 'pda' field goes across the 64-bit
boundary, we need use cmpxchg16b to atomically update it. We only
expose posted-interrupt when X86_FEATURE_CX16 is supported and use
to update it atomically.
Signed-off-by: Feng Wu <feng.wu@intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index bdc52cc..a50468e 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -169,8 +169,26 @@
index = irq_iommu->irte_index + irq_iommu->sub_handle;
irte = &iommu->ir_table->base[index];
- set_64bit(&irte->low, irte_modified->low);
- set_64bit(&irte->high, irte_modified->high);
+#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE)
+ if ((irte->pst == 1) || (irte_modified->pst == 1)) {
+ bool ret;
+
+ ret = cmpxchg_double(&irte->low, &irte->high,
+ irte->low, irte->high,
+ irte_modified->low, irte_modified->high);
+ /*
+ * We use cmpxchg16 to atomically update the 128-bit IRTE,
+ * and it cannot be updated by the hardware or other processors
+ * behind us, so the return value of cmpxchg16 should be the
+ * same as the old value.
+ */
+ WARN_ON(!ret);
+ } else
+#endif
+ {
+ set_64bit(&irte->low, irte_modified->low);
+ set_64bit(&irte->high, irte_modified->high);
+ }
__iommu_flush_cache(iommu, irte, sizeof(*irte));
rc = qi_flush_iec(iommu, index, 0);
@@ -727,7 +745,16 @@
struct intel_iommu *iommu;
if (!disable_irq_post) {
- intel_irq_remap_ops.capability |= 1 << IRQ_POSTING_CAP;
+ /*
+ * If IRTE is in posted format, the 'pda' field goes across the
+ * 64-bit boundary, we need use cmpxchg16b to atomically update
+ * it. We only expose posted-interrupt when X86_FEATURE_CX16
+ * is supported. Actually, hardware platforms supporting PI
+ * should have X86_FEATURE_CX16 support, this has been confirmed
+ * with Intel hardware guys.
+ */
+ if ( cpu_has_cx16 )
+ intel_irq_remap_ops.capability |= 1 << IRQ_POSTING_CAP;
for_each_iommu(iommu, drhd)
if (!cap_pi_support(iommu->cap)) {