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intel_iommu: refine iotlb hash calculation

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Commit 1b2b12376c ("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: 1b2b12376c ("intel-iommu: PASID support")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20230412073510.7158-1-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Jason Wang 2023-04-12 15:35:10 +08:00 • committed by Michael S. Tsirkin
parent 8a9ede6f51
commit ec1a78cee9
2 changed files with 8 additions and 7 deletions
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6
hw/i386/intel_iommu_internal.h
View file

@ -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 */