On 23.05.2023 13:57, Luca Fancellu wrote: >> On 23 May 2023, at 12:53, Jan Beulich <jbeul...@suse.com> wrote: >> On 23.05.2023 13:50, Luca Fancellu wrote: >>>> On 23 May 2023, at 11:31, Jan Beulich <jbeul...@suse.com> wrote: >>>> On 23.05.2023 12:21, Luca Fancellu wrote: >>>>>> On 23 May 2023, at 11:02, Jan Beulich <jbeul...@suse.com> wrote: >>>>>> On 23.05.2023 09:43, Luca Fancellu wrote: >>>>>>> @@ -838,6 +838,22 @@ Controls for how dom0 is constructed on x86 >>>>>>> systems. >>>>>>> >>>>>>> If using this option is necessary to fix an issue, please report a >>>>>>> bug. >>>>>>> >>>>>>> +Enables features on dom0 on Arm systems. >>>>>>> + >>>>>>> +* The `sve` integer parameter enables Arm SVE usage for Dom0 domain >>>>>>> and sets >>>>>>> + the maximum SVE vector length, the option is applicable only to >>>>>>> AArch64 >>>>>>> + guests. >>>>>> >>>>>> Why "guests"? Does the option affect more than Dom0? >>>>> >>>>> I used “guests” because in my mind I was referring to all the aarch64 OS >>>>> that can be used >>>>> as control domain, I can change it if it sounds bad. >>>> >>>> If you means OSes then better also say OSes. But maybe this doesn't need >>>> specifically expressing, by saying e.g. "..., the option is applicable >>>> only on AArch64"? Or can a Dom0 be 32-bit on Arm64 Xen? >>> >>> I think there is no limitation so Dom0 can be 32 bit or 64. Maybe I can say >>> “... AArch64 kernel guests.”? >> >> I'd recommend to avoid the term "guest" when you talk about Dom0 alone. >> Commonly "guest" means ordinary domains only, i.e. in particular excluding >> Dom0. What's wrong with "AArch64 Dom0 kernels"? > > Ok works for me, I will use “AArch64 Dom0 kernels", I thought “guests” were a > generic category > and then we have “privileged guests”, for example Dom0 or driver domain, and > “unprivileged guests” > like DomUs.
Well, yes - "commonly" doesn't mean "always". >>>>>>> + A value equal to 0 disables the feature, this is the default value. >>>>>>> + Values below 0 means the feature uses the maximum SVE vector length >>>>>>> + supported by hardware, if SVE is supported. >>>>>>> + Values above 0 explicitly set the maximum SVE vector length for >>>>>>> Dom0, >>>>>>> + allowed values are from 128 to maximum 2048, being multiple of 128. >>>>>>> + Please note that when the user explicitly specifies the value, if >>>>>>> that value >>>>>>> + is above the hardware supported maximum SVE vector length, the >>>>>>> domain >>>>>>> + creation will fail and the system will stop, the same will occur >>>>>>> if the >>>>>>> + option is provided with a non zero value, but the platform doesn't >>>>>>> support >>>>>>> + SVE. >>>>>> >>>>>> Assuming this also covers the -1 case, I wonder if that isn't a little >>>>>> too >>>>>> strict. "Maximum supported" imo can very well be 0. >>>>> >>>>> Maximum supported, when platforms uses SVE, can be at minimum 128 by arm >>>>> specs. >>>> >>>> When there is SVE - sure. But when there's no SVE, 0 is kind of the implied >>>> length. And I'd view a command line option value of -1 quite okay in that >>>> case: They've asked for the maximum supported, so they'll get 0. No reason >>>> to crash the system during boot. >>> >>> Ok I see what you mean, for example when Kconfig SVE is enabled, but the >>> platform doesn’t >>> have SVE feature, requesting sve=-1 will keep the value to 0, and no system >>> will be stopped. >>> >>> Maybe I can say: >>> >>> “... the same will occur if the option is provided with a positive non zero >>> value, >>> but the platform doesn't support SVE." >> >> Right, provided that matches the implementation. > > Ok I will do the changes, can I retain your R-by? I suppose it covers also > documentation right? I guess whether doc is covered is fuzzy. Since the doc part is Arm- specific, I'd probably consider it not covered with the "!arm" that I appended. But whichever way you look at it, you can keep the tag in place. Jan
