| Message ID | 20230531072413.868673-1-luca.fancellu@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | SVE feature for arm guests | expand |
Hi Luca, On 31/05/2023 08:24, Luca Fancellu wrote: > This serie is introducing the possibility for Dom0 and DomU guests to use > sve/sve2 instructions. > > SVE feature introduces new instruction and registers to improve performances on > floating point operations. > > The SVE feature is advertised using the ID_AA64PFR0_EL1 register, SVE field, and > when available the ID_AA64ZFR0_EL1 register provides additional information > about the implemented version and other SVE feature. > > New registers added by the SVE feature are Z0-Z31, P0-P15, FFR, ZCR_ELx. > > Z0-Z31 are scalable vector register whose size is implementation defined and > goes from 128 bits to maximum 2048, the term vector length will be used to refer > to this quantity. > P0-P15 are predicate registers and the size is the vector length divided by 8, > same size is the FFR (First Fault Register). > ZCR_ELx is a register that can control and restrict the maximum vector length > used by the <x> exception level and all the lower exception levels, so for > example EL3 can restrict the vector length usable by EL3,2,1,0. > > The platform has a maximum implemented vector length, so for every value > written in ZCR register, if this value is above the implemented length, then the > lower value will be used. The RDVL instruction can be used to check what vector > length is the HW using after setting ZCR. > > For an SVE guest, the V0-V31 registers are part of the Z0-Z31, so there is no > need to save them separately, saving Z0-Z31 will save implicitly also V0-V31. > > SVE usage can be trapped using a flag in CPTR_EL2, hence in this serie the > register is added to the domain state, to be able to trap only the guests that > are not allowed to use SVE. > > This serie is introducing a command line parameter to enable Dom0 to use SVE and > to set its maximum vector length that by default is 0 which means the guest is > not allowed to use SVE. Values from 128 to 2048 mean the guest can use SVE with > the selected value used as maximum allowed vector length (which could be lower > if the implemented one is lower). > For DomUs, an XL parameter with the same way of use is introduced and a dom0less > DTB binding is created. > > The context switch is the most critical part because there can be big registers > to be saved, in this serie an easy approach is used and the context is > saved/restored every time for the guests that are allowed to use SVE. > > Luca Fancellu (12): > xen/arm: enable SVE extension for Xen > xen/arm: add SVE vector length field to the domain > xen/arm: Expose SVE feature to the guest > xen/arm: add SVE exception class handling > arm/sve: save/restore SVE context switch > xen/common: add dom0 xen command line argument for Arm > xen: enable Dom0 to use SVE feature > xen/physinfo: encode Arm SVE vector length in arch_capabilities > tools: add physinfo arch_capabilities handling for Arm > xen/tools: add sve parameter in XL configuration > xen/arm: add sve property for dom0less domUs > xen/changelog: Add SVE and "dom0" options to the changelog for Arm The series is now committed. Note that I had to resolve a minor conflict in the CHANGELOG. Cheers,