On Fri, 11 Dec 2020 at 20:07, Eric Biggers <ebiggers@xxxxxxxxxx> wrote: > > On Fri, Dec 11, 2020 at 07:29:04PM +0800, Tony W Wang-oc wrote: > > The driver crc32c-intel match CPUs supporting X86_FEATURE_XMM4_2. > > On platforms with Zhaoxin CPUs supporting this X86 feature, When > > crc32c-intel and crc32c-generic are both registered, system will > > use crc32c-intel because its .cra_priority is greater than > > crc32c-generic. This case expect to use crc32c-generic driver for > > some Zhaoxin CPUs to get performance gain, So remove these Zhaoxin > > CPUs support from crc32c-intel. > > > > Signed-off-by: Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx> > > Does this mean that the performance of the crc32c instruction on those CPUs is > actually slower than a regular C implementation? That's very weird. > This driver does not use CRC instructions, but carryless multiplication and aggregation. So I suppose the pclmulqdq instruction triggers some pathological performance limitation here. That means the crct10dif driver probably needs the same treatment.
