From: mark.rutland@arm.com (Mark Rutland)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64: fix invalidation of wrong __early_cpu_boot_status cacheline
Date: Fri, 15 Apr 2016 11:20:18 +0100 [thread overview]
Message-ID: <20160415102017.GA8021@leverpostej> (raw)
In-Reply-To: <1460715081-16542-1-git-send-email-ard.biesheuvel@linaro.org>
On Fri, Apr 15, 2016 at 12:11:21PM +0200, Ard Biesheuvel wrote:
> In head.S, the str_l macro, which takes a source register, a symbol name
> and a temp register, is used to store a status value to the variable
> __early_cpu_boot_status. Subsequently, the value of the temp register is
> reused to invalidate any cachelines covering this variable.
>
> However, since str_l resolves to
>
> adrp \tmp, \sym
> str \src, [\tmp, :lo12:\sym]
>
> the temp register never actually holds the address of the variable but
> only of the 4 KB window that covers it, and reusing it leads to the
> wrong cacheline being invalidated. So instead, take the address
> explicitly before doing the store, and reuse that value to perform
> the cache invalidation.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>
> This deserves a cc stable, since the macro is always invoked for each CPU
> at boot.
Sounds good, also:
Fixes: bb9052744f4b7ae1 ("arm64: Handle early CPU boot failures")
> Alternatively, we could add a writeback to the str_l macro, but I think
> in general, making any assumptions about the value of a temp register is
> dodgy, so I prefer this approach instead.
Likewise, I prefer this.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Mark.
> arch/arm64/kernel/head.S | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 8b8a3d1e23fb..fafe21e49aab 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -693,7 +693,8 @@ ENDPROC(__secondary_switched)
>
> .macro update_early_cpu_boot_status status, tmp1, tmp2
> mov \tmp2, #\status
> - str_l \tmp2, __early_cpu_boot_status, \tmp1
> + adr_l \tmp1, __early_cpu_boot_status
> + str \tmp2, [\tmp1]
> dmb sy
> dc ivac, \tmp1 // Invalidate potentially stale cache line
> .endm
> --
> 2.5.0
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
next prev parent reply other threads:[~2016-04-15 10:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-15 10:11 [PATCH] arm64: fix invalidation of wrong __early_cpu_boot_status cacheline Ard Biesheuvel
2016-04-15 10:20 ` Mark Rutland [this message]
2016-04-15 10:36 ` Suzuki K Poulose
2016-04-15 11:07 ` Catalin Marinas
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