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    SubjectRe: [PATCH 02/18] arm64: move SCTLR_EL{1,2} assertions to <asm/sysreg.h>
    On Mon, May 14, 2018 at 10:46:24AM +0100, Mark Rutland wrote:
    > Currently we assert that the SCTLR_EL{1,2}_{SET,CLEAR} bits are
    > self-consistent with an assertion in config_sctlr_el1(). This is a bit
    > unusual, since config_sctlr_el1() doesn't make use of these definitions,
    > and is far away from the definitions themselves.
    >
    > We can use the CPP #error directive to have equivalent assertions in
    > <asm/sysreg.h>, next to the definitions of the set/clear bits, which is
    > a bit clearer and simpler.
    >
    > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
    > Cc: Catalin Marinas <catalin.marinas@arm.com>
    > Cc: James Morse <james.morse@arm.com>
    > Cc: Will Deacon <will.deacon@arm.com>
    > ---
    > arch/arm64/include/asm/sysreg.h | 14 ++++++--------
    > 1 file changed, 6 insertions(+), 8 deletions(-)
    >
    > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
    > index 6171178075dc..bd1d1194a5e7 100644
    > --- a/arch/arm64/include/asm/sysreg.h
    > +++ b/arch/arm64/include/asm/sysreg.h
    > @@ -452,9 +452,9 @@
    > SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_WXN | \
    > ENDIAN_CLEAR_EL2 | SCTLR_EL2_RES0)
    >
    > -/* Check all the bits are accounted for */
    > -#define SCTLR_EL2_BUILD_BUG_ON_MISSING_BITS BUILD_BUG_ON((SCTLR_EL2_SET ^ SCTLR_EL2_CLEAR) != ~0)
    > -
    > +#if (SCTLR_EL2_SET ^ SCTLR_EL2_CLEAR) != 0xffffffff
    > +#error "Inconsistent SCTLR_EL2 set/clear bits"
    > +#endif

    Can we have a comment on the != 0xffffffff versus != ~0 here?

    The subtle differences in evaluation semantics between #if and
    other contexts here may well trip people up during maintenance...


    With that, Reviewed-by: Dave Martin <Dave.Martin@arm.com>

    Cheers
    ---Dave

    >
    > /* SCTLR_EL1 specific flags. */
    > #define SCTLR_EL1_UCI (1 << 26)
    > @@ -492,8 +492,9 @@
    > SCTLR_EL1_UMA | SCTLR_ELx_WXN | ENDIAN_CLEAR_EL1 |\
    > SCTLR_EL1_RES0)
    >
    > -/* Check all the bits are accounted for */
    > -#define SCTLR_EL1_BUILD_BUG_ON_MISSING_BITS BUILD_BUG_ON((SCTLR_EL1_SET ^ SCTLR_EL1_CLEAR) != ~0)
    > +#if (SCTLR_EL1_SET ^ SCTLR_EL1_CLEAR) != 0xffffffff
    > +#error "Inconsistent SCTLR_EL1 set/clear bits"
    > +#endif
    >
    > /* id_aa64isar0 */
    > #define ID_AA64ISAR0_TS_SHIFT 52
    > @@ -732,9 +733,6 @@ static inline void config_sctlr_el1(u32 clear, u32 set)
    > {
    > u32 val;
    >
    > - SCTLR_EL2_BUILD_BUG_ON_MISSING_BITS;
    > - SCTLR_EL1_BUILD_BUG_ON_MISSING_BITS;
    > -
    > val = read_sysreg(sctlr_el1);
    > val &= ~clear;
    > val |= set;
    > --
    > 2.11.0
    >
    >
    > _______________________________________________
    > linux-arm-kernel mailing list
    > linux-arm-kernel@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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