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vfio/spapr: Fix page size calculation 

Coverity detected an issue (CID 1421903) with potential call of clz64(0)
which returns 64 which make it do "<<" with a negative number.

This checks the mask and avoids undefined behaviour.

In practice pgsizes and memory_region_iommu_get_min_page_size() always
have some common page sizes and even if they did not, the resulting page
size would be 0x8000.0000.0000.0000 (gcc 9.2) and
ioctl(VFIO_IOMMU_SPAPR_TCE_CREATE) would fail anyway.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-Id: <20200324063912.25063-1-aik@ozlabs.ru>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Alexey Kardashevskiy 2020-03-24 17:39:12 +11:00 committed by David Gibson
parent 3b4f50bd7d
commit 79178edd2a
1 changed files with 3 additions and 3 deletions
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6
hw/vfio/spapr.c
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@ -147,7 +147,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
{
int ret = 0;
IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr);
uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
unsigned entries, bits_total, bits_per_level, max_levels;
struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
long rampagesize = qemu_minrampagesize();
@ -159,8 +159,8 @@ int vfio_spapr_create_window(VFIOContainer *container,
if (pagesize > rampagesize) {
pagesize = rampagesize;
}
pagesize = 1ULL << (63 - clz64(container->pgsizes &
(pagesize | (pagesize - 1))));
pgmask = container->pgsizes & (pagesize | (pagesize - 1));
pagesize = pgmask ? (1ULL << (63 - clz64(pgmask))) : 0;
if (!pagesize) {
error_report("Host doesn't support page size 0x%"PRIx64
", the supported mask is 0x%lx",