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[PATCH V2] intel_iommu: refine iotlb hash calculation
From: |
Jason Wang |
Subject: |
[PATCH V2] intel_iommu: refine iotlb hash calculation |
Date: |
Wed, 12 Apr 2023 15:35:10 +0800 |
Commit 1b2b12376c8 ("intel-iommu: PASID support") takes PASID into
account when calculating iotlb hash like:
static guint vtd_iotlb_hash(gconstpointer v)
{
const struct vtd_iotlb_key *key = v;
return key->gfn | ((key->sid) << VTD_IOTLB_SID_SHIFT) |
(key->level) << VTD_IOTLB_LVL_SHIFT |
(key->pasid) << VTD_IOTLB_PASID_SHIFT;
}
This turns out to be problematic since:
- the shift will lose bits if not converting to uint64_t
- level should be off by one in order to fit into 2 bits
- VTD_IOTLB_PASID_SHIFT is 30 but PASID is 20 bits which will waste
some bits
- the hash result is uint64_t so we will lose bits when converting to
guint
So this patch fixes them by
- converting the keys into uint64_t before doing the shift
- off level by one to make it fit into two bits
- change the sid, lvl and pasid shift to 26, 42 and 44 in order to
take the full width of uint64_t
- perform an XOR to the top 32bit with the bottom 32bit for the final
result to fit guint
Fixes: Coverity CID 1508100
Fixes: 1b2b12376c8 ("intel-iommu: PASID support")
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes since V1:
- perform XOR to avoid losing bits when converting to gint
---
hw/i386/intel_iommu.c | 9 +++++----
hw/i386/intel_iommu_internal.h | 6 +++---
2 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index a62896759c..94d52f4205 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -64,8 +64,8 @@ struct vtd_as_key {
struct vtd_iotlb_key {
uint64_t gfn;
uint32_t pasid;
- uint32_t level;
uint16_t sid;
+ uint8_t level;
};
static void vtd_address_space_refresh_all(IntelIOMMUState *s);
@@ -221,10 +221,11 @@ static gboolean vtd_iotlb_equal(gconstpointer v1,
gconstpointer v2)
static guint vtd_iotlb_hash(gconstpointer v)
{
const struct vtd_iotlb_key *key = v;
+ uint64_t hash64 = key->gfn | ((uint64_t)(key->sid) << VTD_IOTLB_SID_SHIFT)
|
+ (uint64_t)(key->level - 1) << VTD_IOTLB_LVL_SHIFT |
+ (uint64_t)(key->pasid) << VTD_IOTLB_PASID_SHIFT;
- return key->gfn | ((key->sid) << VTD_IOTLB_SID_SHIFT) |
- (key->level) << VTD_IOTLB_LVL_SHIFT |
- (key->pasid) << VTD_IOTLB_PASID_SHIFT;
+ return (guint)((hash64 >> 32) ^ (hash64 & 0xffffffffU));
}
static gboolean vtd_as_equal(gconstpointer v1, gconstpointer v2)
diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index f090e61e11..2e61eec2f5 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -114,9 +114,9 @@
VTD_INTERRUPT_ADDR_FIRST + 1)
/* The shift of source_id in the key of IOTLB hash table */
-#define VTD_IOTLB_SID_SHIFT 20
-#define VTD_IOTLB_LVL_SHIFT 28
-#define VTD_IOTLB_PASID_SHIFT 30
+#define VTD_IOTLB_SID_SHIFT 26
+#define VTD_IOTLB_LVL_SHIFT 42
+#define VTD_IOTLB_PASID_SHIFT 44
#define VTD_IOTLB_MAX_SIZE 1024 /* Max size of the hash table */
/* IOTLB_REG */
--
2.25.1
- [PATCH V2] intel_iommu: refine iotlb hash calculation,
Jason Wang <=