linux-kernel - Re: [PATCH 03/15] arm64: kvm: Fix symbol dependency in __hyp_call_panic

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Date:   Thu, 07 May 2020 14:22:34 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Will Deacon <will@...nel.org>, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/15] arm64: kvm: Fix symbol dependency in __hyp_call_panic_nvhe

On Thu, 30 Apr 2020 15:48:19 +0100,
David Brazdil <dbrazdil@...gle.com> wrote:
> 
> __hyp_call_panic_nvhe contains inline assembly which did not declare
> its dependency on the __hyp_panic_string symbol.
> 
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>
> ---
>  arch/arm64/kvm/hyp/switch.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 8a1e81a400e0..7a7c08029d81 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -836,7 +836,7 @@ static void __hyp_text __hyp_call_panic_nvhe(u64 spsr, u64 elr, u64 par,
>  	 * making sure it is a kernel address and not a PC-relative
>  	 * reference.
>  	 */
> -	asm volatile("ldr %0, =__hyp_panic_string" : "=r" (str_va));
> +	asm volatile("ldr %0, =%1" : "=r" (str_va) : "S" (__hyp_panic_string));
>  
>  	__hyp_do_panic(str_va,
>  		       spsr, elr,
> -- 
> 2.26.1
> 
> 

What breaks without this constraint? Is it a fix that should go in
early? Otherwise looks good.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.