On 12/13/2017 11:15 AM, Alex Williamson wrote:
On Wed, 13 Dec 2017 10:41:47 -0600
"Hook, Gary" <gh...@amd.com> wrote:
On 12/13/2017 9:58 AM, Alex Williamson wrote:
On Wed, 13 Dec 2017 15:13:55 +0800
Peter Xu <pet...@redhat.com> wrote:
On Tue, Dec 12, 2017 at 03:43:08PM -0700, Alex Williamson wrote:
[...]
diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 9a7ffd13c7f0..87888b102057 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1345,7 +1345,9 @@ void qi_flush_dev_iotlb(struct intel_iommu *iommu, u16
sid, u16 qdep,
struct qi_desc desc;
if (mask) {
- BUG_ON(addr & ((1 << (VTD_PAGE_SHIFT + mask)) - 1));
+ BUG_ON((mask > MAX_AGAW_PFN_WIDTH) ||
+ ((mask == MAX_AGAW_PFN_WIDTH) && addr) ||
+ (addr & ((1 << (VTD_PAGE_SHIFT + mask)) - 1)));
Could it work if we just use 1ULL instead of 1 here? Thanks,
In either case we're talking about shifting off the end of the
variable, which I understand to be undefined. Right? Thanks,
How so? Bits fall off the left (MSB) end, zeroes fill in the right (LSB)
end. I believe that behavior is pretty set.
Maybe I'm relying too much on stackoverflow, but:
https://stackoverflow.com/questions/11270492/what-does-the-c-standard-say-about-bitshifting-more-bits-than-the-width-of-type
No, probably not. I don't have my copy of c99 handy, so can't check it.
But it is beyond me why any compiler implementation would choose to use
a rotate instead of a shift... probably a performance issue.
So, yeah, when you have silly parameters, you get what you get.
I'll stick to my suggestion. Which seems unambiguous... but I could be
wrong.
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