Messages in this thread | | | Date | Sun, 24 Apr 2022 17:27:09 +0800 | Subject | Re: [PATCH] arm64/sme: Add hwcap for Scalable Matrix Extension | From | Tianjia Zhang <> |
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Hi Mark,
On 4/19/22 9:58 PM, Mark Brown wrote: > On Fri, Apr 15, 2022 at 10:25:33AM +0800, Tianjia Zhang wrote: >> On 4/14/22 8:02 PM, Mark Brown wrote: >>> On Thu, Apr 14, 2022 at 07:55:44PM +0800, Tianjia Zhang wrote: > >>> 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. > > I see. Unfortunately all the new registers mean that we really need to > define all the ABI as soon as we enable anything and the only thing we > can really skip out on when doing initial enablement is KVM (which I > have in fact skipped for the time being, I'll look at that at some point > after the initial support is landed). > >> 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. > > I'm not aware of anything, but I am mostly focused on the OS support > rather than any of the actual mathematical operations that are more the > point of these architecture features so I might be missing something. > >>> 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? > > Other than verifying that the series doesn't cause trouble for systems > without SME
Thanks for your reply, I have indirectly implemented the functionality of the REVD instruction using the tbl instruction on a machine that does not support SME.
For this group of patchsets, I will do some tests later, which may take a long time, and there is currently no exclusive machine at hand.
Best regards, Tianjia
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