[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2 1/2] gnttab: adjust pin count overflow checks
On 15.01.2021 16:38, Andrew Cooper wrote: > On 15/01/2021 15:14, Jan Beulich wrote: >> It's at least odd to check counters which aren't going to be >> incremented, resulting in failure just because prior operations may >> have left an entry in an unusual state. > > I wouldn't say it's an unusual state. It can happen legally when you > map the same gref 128 times > > Why a guest would do this in normal operation is a different question. Hence the "unusual". > Perhaps "prior operations may have reached the refcount limit" ? Fine with me. >> And it's also not helpful to >> use open-coded literal numbers in these checks. >> >> Calculate the increment values first and derive from them the mask to >> use in the checks. >> >> Also move the pin count checks ahead of the calculation of the status >> (and for copy also sha2) pointers: They're not needed in the failure >> cases, and this way the compiler may also have an easier time keeping >> the variables at least transiently in registers for the subsequent uses. >> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> > > Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Thanks. Jan
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