[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] MPIDR register usage in ARMv8
On Wed, 2014-04-16 at 11:23 +0530, Vijay Kilari wrote: > Hi Ian, > > I understand that arm64/head.S is using MPIDR definitions > from xen/include/asm-arm/processor.h which is valid for arm32 but > not for ARMv8 as below > > /* MPIDR Multiprocessor Affinity Register */ > #define _MPIDR_UP (30) > #define MPIDR_UP (_AC(1,U) << _MPIDR_UP) > #define _MPIDR_SMP (31) > #define MPIDR_SMP (_AC(1,U) << _MPIDR_SMP) > #define MPIDR_AFF0_SHIFT (0) > #define MPIDR_AFF0_MASK (_AC(0xff,U) << MPIDR_AFF0_SHIFT) > #define MPIDR_HWID_MASK _AC(0xffffff,U) > #define MPIDR_INVALID (~MPIDR_HWID_MASK) > > The same is used in arm64/head.S checking for bit 31 (_MPIDR_SMP) which is not > valid in MPIDR_EL1 register definition It's mostly there for symmetry with the arm32 code, and since arm64 mandates read-as-one (not strictly speaking invalid) to match the meaning of the bit patterns on arm32 to the requirements of arm64 I think it is mostly harmless and I suppose it is future proof against the possibility that future v8 revisions might reintroduce the meanings of those bits. > also MPIDR_HWID_MASK should > be updated for ARMv8 No harm in adding AFF3 into the mix I suppose. > > arm64/head.s: > > mrs x0, mpidr_el1 > tbz x0, _MPIDR_SMP, 1f /* Multiprocessor extension not > supported? */ > tbnz x0, _MPIDR_UP, 1f /* Uniprocessor system? */ > > mov x13, #(~MPIDR_HWID_MASK) > bic x24, x0, x13 /* Mask out flags to get CPU ID */ > 1: > > Do you agree that this requires change? _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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