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    Subject[PATCH v7 13/25] arm64: alternative: Allow alternative status checking per cpufeature
    Date
    In preparation for the application of alternatives at different points
    during the boot process, provide the possibility to check whether
    alternatives for a feature of interest was already applied instead of
    having a global boolean for all alternatives.

    Make VHE enablement code check for the VHE feature instead of considering
    all alternatives.

    Signed-off-by: Julien Thierry <julien.thierry@arm.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
    Cc: Marc Zyngier <Marc.Zyngier@arm.com>
    Cc: Christoffer Dall <Christoffer.Dall@arm.com>
    ---
    arch/arm64/include/asm/alternative.h | 3 +--
    arch/arm64/kernel/alternative.c | 21 +++++++++++++++++----
    arch/arm64/kernel/cpufeature.c | 2 +-
    3 files changed, 19 insertions(+), 7 deletions(-)

    diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
    index 4b650ec..9806a23 100644
    --- a/arch/arm64/include/asm/alternative.h
    +++ b/arch/arm64/include/asm/alternative.h
    @@ -14,8 +14,6 @@
    #include <linux/stddef.h>
    #include <linux/stringify.h>

    -extern int alternatives_applied;
    -
    struct alt_instr {
    s32 orig_offset; /* offset to original instruction */
    s32 alt_offset; /* offset to replacement instruction */
    @@ -28,6 +26,7 @@ typedef void (*alternative_cb_t)(struct alt_instr *alt,
    __le32 *origptr, __le32 *updptr, int nr_inst);

    void __init apply_alternatives_all(void);
    +bool alternative_is_applied(u16 cpufeature);

    #ifdef CONFIG_MODULES
    void apply_alternatives_module(void *start, size_t length);
    diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
    index b5d6039..c947d22 100644
    --- a/arch/arm64/kernel/alternative.c
    +++ b/arch/arm64/kernel/alternative.c
    @@ -32,13 +32,23 @@
    #define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset)
    #define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset)

    -int alternatives_applied;
    +static int all_alternatives_applied;
    +
    +static DECLARE_BITMAP(applied_alternatives, ARM64_NCAPS);

    struct alt_region {
    struct alt_instr *begin;
    struct alt_instr *end;
    };

    +bool alternative_is_applied(u16 cpufeature)
    +{
    + if (WARN_ON(cpufeature >= ARM64_NCAPS))
    + return false;
    +
    + return test_bit(cpufeature, applied_alternatives);
    +}
    +
    /*
    * Check if the target PC is within an alternative block.
    */
    @@ -192,6 +202,9 @@ static void __apply_alternatives(void *alt_region, bool is_module)
    dsb(ish);
    __flush_icache_all();
    isb();
    +
    + /* We applied all that was available */
    + bitmap_copy(applied_alternatives, cpu_hwcaps, ARM64_NCAPS);
    }
    }

    @@ -208,14 +221,14 @@ static int __apply_alternatives_multi_stop(void *unused)

    /* We always have a CPU 0 at this point (__init) */
    if (smp_processor_id()) {
    - while (!READ_ONCE(alternatives_applied))
    + while (!READ_ONCE(all_alternatives_applied))
    cpu_relax();
    isb();
    } else {
    - BUG_ON(alternatives_applied);
    + BUG_ON(all_alternatives_applied);
    __apply_alternatives(&region, false);
    /* Barriers provided by the cache flushing */
    - WRITE_ONCE(alternatives_applied, 1);
    + WRITE_ONCE(all_alternatives_applied, 1);
    }

    return 0;
    diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
    index 4426b5b..b7539c7 100644
    --- a/arch/arm64/kernel/cpufeature.c
    +++ b/arch/arm64/kernel/cpufeature.c
    @@ -1068,7 +1068,7 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
    * that, freshly-onlined CPUs will set tpidr_el2, so we don't need to
    * do anything here.
    */
    - if (!alternatives_applied)
    + if (!alternative_is_applied(ARM64_HAS_VIRT_HOST_EXTN))
    write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
    }
    #endif
    --
    1.9.1
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