linux-kernel - Re: [PATCH V2 5/9] arm64: exception: handle instruction abort at current EL

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Date:	Wed, 6 Apr 2016 16:36:46 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Tyler Baicar <tbaicar@...eaurora.org>, fu.wei@...aro.org,
	timur@...eaurora.org, harba@...eaurora.org,
	rruigrok@...eaurora.org, ahs3@...hat.com, catalin.marinas@....com,
	will.deacon@....com, rjw@...ysocki.net, lenb@...nel.org,
	matt@...eblueprint.co.uk, robert.moore@...el.com,
	lv.zheng@...el.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-efi@...r.kernel.org, devel@...ica.org
Cc:	Naveen Kaje <nkaje@...eaurora.org>
Subject: Re: [PATCH V2 5/9] arm64: exception: handle instruction abort at
 current EL

On 06/04/16 16:12, Tyler Baicar wrote:
> Add a handler for instruction aborts at the current EL
> (ESR_ELx_EC_IABT_CUR) so they are no longer handled in el1_inv.
> This allows firmware first handling for possible SEA
> (Synchronous External Abort) caused instruction abort at
> current EL.
> 
> Signed-off-by: Tyler Baicar <tbaicar@...eaurora.org>
> Signed-off-by: Naveen Kaje <nkaje@...eaurora.org>
> ---
>  arch/arm64/kernel/entry.S | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 12e8d2b..f257856 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -336,6 +336,8 @@ el1_sync:
>  	lsr	x24, x1, #ESR_ELx_EC_SHIFT	// exception class
>  	cmp	x24, #ESR_ELx_EC_DABT_CUR	// data abort in EL1
>  	b.eq	el1_da
> +	cmp	x24, #ESR_ELx_EC_IABT_CUR	// instruction abort in EL1
> +	b.eq	el1_ia
>  	cmp	x24, #ESR_ELx_EC_SYS64		// configurable trap
>  	b.eq	el1_undef
>  	cmp	x24, #ESR_ELx_EC_SP_ALIGN	// stack alignment exception
> @@ -363,6 +365,23 @@ el1_da:
>  	// disable interrupts before pulling preserved data off the stack
>  	disable_irq
>  	kernel_exit 1
> +el1_ia:
> +	/*
> +	 * Instruction abort handling
> +	 */
> +	mrs	x0, far_el1
> +	enable_dbg
> +	// re-enable interrupts if they were enabled in the aborted context
> +	tbnz	x23, #7, 1f			// PSR_I_BIT
> +	enable_irq
> +1:
> +	orr	x1, x1, #1 << 24		// use reserved ISS bit for instruction aborts
> +	mov	x2, sp				// struct pt_regs
> +	bl	do_mem_abort
> +
> +	// disable interrupts before pulling preserved data off the stack
> +	disable_irq
> +	kernel_exit 1
>  el1_sp_pc:
>  	/*
>  	 * Stack or PC alignment exception handling
> 

What happens if you were running at EL2 when this faults gets injected?
It looks like KVM needs something similar, doesn't it?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...