Hi Mark,
On 4/14/22 8:02 PM, Mark Brown wrote:
On Thu, Apr 14, 2022 at 07:55:44PM +0800, Tianjia Zhang wrote:
Allow userspace to detect support for SME (Scalable Matrix Extension)
by providing a hwcap for it, using the official feature name FEAT_SME,
declared in ARM DDI 0487H.a specification.
There's already a hwcap for the core feature and all the subfeatures
added as part of the series I've been posting for SME:
https://lore.kernel.org/linux-arm-kernel/20220408114328.1401034-1-broonie@xxxxxxxxxx/
Why add something independently, especially given that there is no way
for userspace to do anything constructive with the feature without the
rest of the kernel support? Any attempt to use SME instructions without
kernel support will trap and generate a SIGILL even if the feature is
present in hardware.
Great job, I encountered the issue of invalid REVD (requires FEAT_SME)
instruction when developing SVE2 programs, so I plan to gradually
support SME in the kernel, thanks for your contribution, you can ignore
my patch.
In addition, I would like to ask a question, whether there is an
alternative SVE2 instruction for the REVD instruction that can complete
this operation, if the machine does not support SME.
Do you have a system with SME that you're trying to use? Review/testing
on the current series would be appreciated.
Unfortunately, the value currently read by my machine ID_AA64PFR1_EL1
register is 0x121. It seems that the hardware does not support SME. Is
there any other help I can provide?
Kind regards,
Tianjia
