[Xen-devel] MPIDR register usage in ARMv8

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

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 also MPIDR_HWID_MASK should
be updated for ARMv8

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?

Regards
Vijay

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