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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Julien Grall <julien.grall@arm.com>
Cc: andre.przywara@arm.com, sstabellini@kernel.org,
	steve.capper@arm.com, wei.chen@arm.com, xen-devel@lists.xen.org
Subject: Re: [PATCH v3 09/16] xen/arm: Introduce alternative runtime patching
Date: Tue, 7 Jun 2016 13:24:57 -0400	[thread overview]
Message-ID: <20160607172457.GA14200@char.us.oracle.com> (raw)
In-Reply-To: <1465315583-1278-10-git-send-email-julien.grall@arm.com>

> +
> +/*
> + * We might be patching the stop_machine state machine, so implement a
> + * really simple polling protocol here.
> + */
> +static int __apply_alternatives_multi_stop(void *unused)
> +{
> +    static int patched = 0;
> +    struct alt_region region = {
> +        .begin = __alt_instructions,
> +        .end = __alt_instructions_end,
> +    };
> +
> +    /* We always have a CPU 0 at this point (__init) */
> +    if ( smp_processor_id() )
> +    {
> +        while ( !read_atomic(&patched) )
> +            cpu_relax();
> +        isb();
> +    }
> +    else
> +    {
> +        int ret;
> +
> +        BUG_ON(patched);
> +        ret = __apply_alternatives(&region);
> +        /* The patching is not expected to fail during boot. */
> +        BUG_ON(ret != 0);
> +
> +        /* Barriers provided by the cache flushing */

Could you add the stop at the end here (and above in the 'We always have..)'?

> +        write_atomic(&patched, 1);
> +    }
> +
> +    return 0;
> +}
> +
> +/*
> + * This function should only be called during boot and before CPU0 jump

Would it make sense to then have an ASSERT or BUG on:

SYS_STATE_early_boot ?

> + * into the idle_loop.
> + */
> +void __init apply_alternatives_all(void)

s/apply_alternatives_all/apply_alternatives_init/ ?

> +{
> +    int ret;
> +
> +	/* better not try code patching on a live SMP system */

Something is off with this comment (wrong column). And while
at it you could also add the '.' at the end.

> +    ret = stop_machine_run(__apply_alternatives_multi_stop, NULL, NR_CPUS);
> +
> +    /* stop_machine_run should never fail at this stage of the boot */

Missing stpo.
> +    BUG_ON(ret);
> +}
> +
..snip..
> diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> index 1f010bd..495f9d8 100644
> --- a/xen/arch/arm/xen.lds.S
> +++ b/xen/arch/arm/xen.lds.S
> @@ -129,6 +129,9 @@ SECTIONS
>         _sinittext = .;
>         *(.init.text)
>         _einittext = .;
> +#ifdef CONFIG_ALTERNATIVE
> +       *(.altinstr_replacement)
> +#endif

This is outside the _einittext? x86 looks to have .altinstr_replacement
inside the _einittext.

>    } :text
>    . = ALIGN(PAGE_SIZE);
>    .init.data : {
> @@ -167,6 +170,13 @@ SECTIONS
>         *(.xsm_initcall.init)
>         __xsm_initcall_end = .;
>    } :text
> +#ifdef CONFIG_ALTERNATIVE
> +  .init.alternatives : {
> +      __alt_instructions = .;
> +      *(.altinstructions)
> +      __alt_instructions_end = .;
> +  }
> +#endif
>    __init_end_efi = .;
>    . = ALIGN(STACK_SIZE);
>    __init_end = .;

Otherwise it looks OK to me.

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  reply	other threads:[~2016-06-07 17:24 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-07 16:06 [PATCH v3 00/16] xen/arm: Introduce alternative runtime patching for ARM64 Julien Grall
2016-06-07 16:06 ` [PATCH v3 01/16] xen/arm: Makefile: Sort the entries alphabetically Julien Grall
2016-06-07 16:06 ` [PATCH v3 02/16] xen/arm: Include the header asm-arm/system.h in asm-arm/page.h Julien Grall
2016-06-07 16:06 ` [PATCH v3 03/16] xen/arm: Add macros to handle the MIDR Julien Grall
2016-06-07 16:06 ` [PATCH v3 04/16] xen/arm: Add cpu_hwcap bitmap Julien Grall
2016-06-07 16:06 ` [PATCH v3 05/16] xen/arm64: Add an helper to invalidate all instruction caches Julien Grall
2016-06-07 16:06 ` [PATCH v3 06/16] xen/arm: arm64: Move the define BRK_BUG_FRAME into a separate header Julien Grall
2016-06-07 16:06 ` [PATCH v3 07/16] xen/arm: arm64: Reserve a brk immediate to fault on purpose Julien Grall
2016-06-07 16:06 ` [PATCH v3 08/16] xen/arm: arm64: Add helpers to decode and encode branch instructions Julien Grall
2016-06-07 16:06 ` [PATCH v3 09/16] xen/arm: Introduce alternative runtime patching Julien Grall
2016-06-07 17:24   ` Konrad Rzeszutek Wilk [this message]
2016-06-08  9:39     ` Julien Grall
2016-06-08 18:17       ` Konrad Rzeszutek Wilk
2016-06-08 18:22         ` Julien Grall
2016-06-08 18:35           ` Konrad Rzeszutek Wilk
2016-06-09 13:33   ` Julien Grall
2016-06-07 16:06 ` [PATCH v3 10/16] xen/arm: cpufeature: Provide an helper to check if a capability is supported Julien Grall
2016-06-22  9:59   ` Stefano Stabellini
2016-06-22 10:09     ` Julien Grall
2016-06-22 10:14       ` Stefano Stabellini
2016-06-07 16:06 ` [PATCH v3 11/16] xen/arm: Detect silicon revision and set cap bits accordingly Julien Grall
2016-06-22 10:00   ` Stefano Stabellini
2016-06-07 16:06 ` [PATCH v3 12/16] xen/arm: Document the errata implemented in Xen Julien Grall
2016-06-22 10:03   ` Stefano Stabellini
2016-06-07 16:06 ` [PATCH v3 13/16] xen/arm: arm64: Add Cortex-A53 cache errata workaround Julien Grall
2016-06-22 10:04   ` Stefano Stabellini
2016-06-07 16:06 ` [PATCH v3 14/16] xen/arm: arm64: Add cortex-A57 erratum 832075 workaround Julien Grall
2016-06-22 10:10   ` Stefano Stabellini
2016-06-07 16:06 ` [PATCH v3 15/16] xen/arm: traps: Don't inject a fault if the translation VA -> IPA fails Julien Grall
2016-06-07 16:06 ` [PATCH v3 16/16] xen/arm: arm64: Document Cortex-A57 erratum 834220 Julien Grall
2016-06-14 12:15   ` Julien Grall
2016-06-22 10:08   ` Stefano Stabellini
2016-06-22 10:18     ` Julien Grall
2016-06-22 10:37       ` Stefano Stabellini

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