linux-kernel - Re: [PATCH v2] ARM: kernel: Fix interrupted SMC calls

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Date:   Mon, 1 Feb 2021 18:06:02 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     linux@...linux.org.uk, will@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bjorn.andersson@...aro.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2] ARM: kernel: Fix interrupted SMC calls

Hi,

On Mon, Jan 18, 2021 at 11:40:40PM +0530, Manivannan Sadhasivam wrote:
> On Qualcomm ARM32 platforms, the SMC call can return before it has
> completed. If this occurs, the call can be restarted, but it requires
> using the returned session ID value from the interrupted SMC call.
> 
> The ARM32 SMCC code already has the provision to add platform specific
> quirks for things like this. So let's make use of it and add the
> Qualcomm specific quirk (ARM_SMCCC_QUIRK_QCOM_A6) used by the QCOM_SCM
> driver.
> 
> This change is similar to the below one added for ARM64 a while ago:
> commit 82bcd087029f ("firmware: qcom: scm: Fix interrupted SCM calls")
> 
> Without this change, the Qualcomm ARM32 platforms like SDX55 will return
> -EINVAL for SMC calls used for modem firmware loading and validation.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

A gentle ping on this patch!

Thanks,
Mani

> ---
> 
> Changes in v2:
> 
> * Preserved callee saved registers and used the registers r4, r5 which
>   are getting pushed onto the stack.
> 
>  arch/arm/kernel/asm-offsets.c |  3 +++
>  arch/arm/kernel/smccc-call.S  | 11 ++++++++++-
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
> index a1570c8bab25..2e2fa6fc2d4f 100644
> --- a/arch/arm/kernel/asm-offsets.c
> +++ b/arch/arm/kernel/asm-offsets.c
> @@ -23,6 +23,7 @@
>  #include <asm/vdso_datapage.h>
>  #include <asm/hardware/cache-l2x0.h>
>  #include <linux/kbuild.h>
> +#include <linux/arm-smccc.h>
>  #include "signal.h"
>  
>  /*
> @@ -147,6 +148,8 @@ int main(void)
>    DEFINE(SLEEP_SAVE_SP_PHYS,	offsetof(struct sleep_save_sp, save_ptr_stash_phys));
>    DEFINE(SLEEP_SAVE_SP_VIRT,	offsetof(struct sleep_save_sp, save_ptr_stash));
>  #endif
> +  DEFINE(ARM_SMCCC_QUIRK_ID_OFFS,	offsetof(struct arm_smccc_quirk, id));
> +  DEFINE(ARM_SMCCC_QUIRK_STATE_OFFS,	offsetof(struct arm_smccc_quirk, state));
>    BLANK();
>    DEFINE(DMA_BIDIRECTIONAL,	DMA_BIDIRECTIONAL);
>    DEFINE(DMA_TO_DEVICE,		DMA_TO_DEVICE);
> diff --git a/arch/arm/kernel/smccc-call.S b/arch/arm/kernel/smccc-call.S
> index 00664c78faca..931df62a7831 100644
> --- a/arch/arm/kernel/smccc-call.S
> +++ b/arch/arm/kernel/smccc-call.S
> @@ -3,7 +3,9 @@
>   * Copyright (c) 2015, Linaro Limited
>   */
>  #include <linux/linkage.h>
> +#include <linux/arm-smccc.h>
>  
> +#include <asm/asm-offsets.h>
>  #include <asm/opcodes-sec.h>
>  #include <asm/opcodes-virt.h>
>  #include <asm/unwind.h>
> @@ -27,7 +29,14 @@ UNWIND(	.fnstart)
>  UNWIND(	.save	{r4-r7})
>  	ldm	r12, {r4-r7}
>  	\instr
> -	pop	{r4-r7}
> +	ldr	r4, [sp, #36]
> +	cmp	r4, #0
> +	beq	1f			// No quirk structure
> +	ldr     r5, [r4, #ARM_SMCCC_QUIRK_ID_OFFS]
> +	cmp     r5, #ARM_SMCCC_QUIRK_QCOM_A6
> +	bne	1f			// No quirk present
> +	str	r6, [r4, #ARM_SMCCC_QUIRK_STATE_OFFS]
> +1:	pop	{r4-r7}
>  	ldr	r12, [sp, #(4 * 4)]
>  	stm	r12, {r0-r3}
>  	bx	lr
> -- 
> 2.25.1
>