Hi Oliver, On 10/28/24 17:56, Oliver Upton wrote: > On Mon, Oct 28, 2024 at 04:48:18PM +0000, Peter Maydell wrote: >> On Mon, 28 Oct 2024 at 16:35, Daniel P. Berrangé <berra...@redhat.com> wrote: >>> On Mon, Oct 28, 2024 at 04:16:31PM +0000, Peter Maydell wrote: >>>> On Fri, 25 Oct 2024 at 14:24, Daniel P. Berrangé <berra...@redhat.com> >>>> wrote: >>>>> On Fri, Oct 25, 2024 at 03:18:25PM +0200, Eric Auger wrote: >>>>>> On 10/25/24 15:06, Daniel P. Berrangé wrote: >>>>>>> Also, is this naming convention really the same one that users >>>>>>> will see when they look at /proc/cpuinfo to view features ? It >>>>>> No it is not. I do agree that the custom cpu model is very low level. It >>>>>> is very well suited to test all series turning ID regs as writable but >>>>>> this would require an extra layer that adapts /proc/cpuinfo feature >>>>>> level to this regid/field abstraction. >>>>>> >>>>>> In /cpu/proc you will see somethink like: >>>>>> Features : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp >>>>>> asimdhp cpuid asimdrdm lrcpc dcpop asimddp >>>>> Right, IMHO, this is the terminology that QEMU must use in user >>>>> facing APIs. >>>> /proc/cpuinfo's naming is rather weird for historical >>>> reasons (for instance there is only one FEAT_FP16 feature >>>> but cpuinfo lists "fphp" and "asimdhp" separately). >>> There's plenty of wierd history in x86 too. In this >>> case I might suggest just picking one of the two >>> common names, and ignoring the other. >>> >>> If we really wanted to, we could alias the 2nd name >>> to the first, but its likely not worth the bother. >> Or we could use the standard set of architectural >> feature names, and not have the problem at all, and not >> have to document what we mean by our nonstandard names. > +1 > > There's existing documentation [*] for the standard feature names, which > provides: > > - A short description of what the feature does > - Any dependencies a particular feature has (e.g.FEAT_VHE implies > FEAT_LSE, FEAT_Debugv8p1, and FEAT_AA64EL2) > - The register fields/values that are used to discover the feature. > > This seems like the most user-friendly option... > > [*]: https://developer.arm.com/documentation/109697/2024_09
Was just wondering if all the writable ID reg fields were associated to an official FEAT_ listed in this feature list. Let's take for instance CTR_EL0.DIC. Is it associated to a given extension or is it just implementation defined? Thanks Eric >
