iommu/amd: Do not flush IRTE when only updating isRun and destination fields

According to the recent update in the AMD IOMMU spec [1], the IsRun and
Destination fields of the Interrupt Remapping Table Entry (IRTE) are not
cached by the IOMMU hardware.

Therefore, do not issue the INVALIDATE_INTERRUPT_TABLE command when
updating IRTE[IsRun] and IRTE[Destination] when IRTE[GuestMode]=1, which
should help improve IOMMU AVIC/x2AVIC performance.

References:
[1] AMD IOMMU Spec Revision (Rev 3.08-PUB)
(Link: https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/specifications/48882_IOMMU.pdf)

Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Link: https://lore.kernel.org/r/20231017144236.8287-1-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: ssuthiku-amd

drivers/iommu/amd/iommu.c

@@ -3111,8 +3111,8 @@ static int alloc_irq_index(struct amd_iommu *iommu, u16 devid, int count,
 	return index;
 }
 
-static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
-			  struct irte_ga *irte)
+static int __modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
+			    struct irte_ga *irte)
 {
 	struct irq_remap_table *table;
 	struct irte_ga *entry;
@@ -3139,6 +3139,18 @@ static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
 
 	raw_spin_unlock_irqrestore(&table->lock, flags);
 
+	return 0;
+}
+
+static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
+			  struct irte_ga *irte)
+{
+	bool ret;
+
+	ret = __modify_irte_ga(iommu, devid, index, irte);
+	if (ret)
+		return ret;
+
 	iommu_flush_irt_and_complete(iommu, devid);
 
 	return 0;
@@ -3822,8 +3834,8 @@ int amd_iommu_update_ga(int cpu, bool is_run, void *data)
 	}
 	entry->lo.fields_vapic.is_run = is_run;
 
-	return modify_irte_ga(ir_data->iommu, ir_data->irq_2_irte.devid,
-			      ir_data->irq_2_irte.index, entry);
+	return __modify_irte_ga(ir_data->iommu, ir_data->irq_2_irte.devid,
+				ir_data->irq_2_irte.index, entry);
 }
 EXPORT_SYMBOL(amd_iommu_update_ga);
 #endif