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    SubjectRe: [PATCH v2 16/22] arm64/debug: Make use of the system wide safe value
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    On 08/10/15 12:11, Catalin Marinas wrote:
    > On Mon, Oct 05, 2015 at 06:02:05PM +0100, Suzuki K. Poulose wrote:
    >> @@ -137,13 +138,17 @@ extern struct pmu perf_ops_bp;
    >> /* Determine number of BRP registers available. */
    >> static inline int get_num_brps(void)
    >> {
    >> - return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1;
    >> + return 1 +
    >> + cpuid_feature_extract_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
    >> + ID_AA64DFR0_BRPS_SHIFT);
    >> }
    >
    > cpuid_feature_extract_field() is fine but we should we bother with
    > read_system_reg vs just read_cpuid?
    > Similar question for patch 17/22.

    Well, we would have already TAINTed the kernel, if these fields are different.
    It is just the matter of, whether we want to provide the safer value on a tainted
    kernel or not. I am open to suggestions.


    Thanks
    Suzuki



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