On Sun, Nov 21, 2021 at 03:14:20PM +0100, Stephan Müller wrote: > The APT compares the current time stamp with a pre-set value. The > current code only considered the 4 LSB only. Yet, after reviews by > mathematicians of the user space Jitter RNG version >= 3.1.0, it was > concluded that the APT can be calculated on the 32 LSB of the time > delta. Thi change is applied to the kernel. > > This fixes a bug where an AMD EPYC fails this test as its RDTSC value > contains zeros in the LSB. The most appropriate fix would have been to > apply a GCD calculation and divide the time stamp by the GCD. Yet, this > is a significant code change that will be considered for a future > update. Note, tests showed that constantly the GCD always was 32 on > these systems, i.e. the 5 LSB were always zero (thus failing the APT > since it only considered the 4 LSB for its calculation). > > Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx> > --- > crypto/jitterentropy.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) Patch applied. Thanks. -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
