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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v7 07/12] xen: enable Dom0 to use SVE feature
> On 23 May 2023, at 11:02, Jan Beulich <jbeulich@xxxxxxxx> wrote: > > On 23.05.2023 09:43, Luca Fancellu wrote: >> Add a command line parameter to allow Dom0 the use of SVE resources, >> the command line parameter sve=<integer>, sub argument of dom0=, >> controls the feature on this domain and sets the maximum SVE vector >> length for Dom0. >> >> Add a new function, parse_signed_integer(), to parse an integer >> command line argument. >> >> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx> > > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> # !arm > >> --- a/docs/misc/xen-command-line.pandoc >> +++ b/docs/misc/xen-command-line.pandoc >> @@ -777,9 +777,9 @@ Specify the bit width of the DMA heap. >> >> ### dom0 >> = List of [ pv | pvh, shadow=<bool>, verbose=<bool>, >> - cpuid-faulting=<bool>, msr-relaxed=<bool> ] >> + cpuid-faulting=<bool>, msr-relaxed=<bool> ] (x86) >> >> - Applicability: x86 >> + = List of [ sve=<integer> ] (Arm) > > While in the text below you mention this is Arm64 only, I think the tag > here would better express this as well. Ok I can use Arm64 instead if there is no opposition from others > >> @@ -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. > >> + 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. > > Jan
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