[1/2] arm64: kernel: Add SMC Session ID to results
diff mbox

Message ID 1471672274-19317-2-git-send-email-andy.gross@linaro.org
State New, archived
Headers show

Commit Message

Andy Gross Aug. 20, 2016, 5:51 a.m. UTC
This patch adds the SMC Session ID to the results passed back from SMC
calls.  The Qualcomm SMC implementation provides for interrupted SMC
functions.  When this occurs, the SMC call will return a session ID that
is required to be used when resuming the interrupted SMC call.

Signed-off-by: Andy Gross <andy.gross@linaro.org>
---
 arch/arm64/kernel/asm-offsets.c | 1 +
 arch/arm64/kernel/smccc-call.S  | 1 +
 include/linux/arm-smccc.h       | 4 +++-
 3 files changed, 5 insertions(+), 1 deletion(-)

Comments

Will Deacon Aug. 22, 2016, 1:43 p.m. UTC | #1
On Sat, Aug 20, 2016 at 12:51:13AM -0500, Andy Gross wrote:
> This patch adds the SMC Session ID to the results passed back from SMC
> calls.  The Qualcomm SMC implementation provides for interrupted SMC
> functions.  When this occurs, the SMC call will return a session ID that
> is required to be used when resuming the interrupted SMC call.
> 
> Signed-off-by: Andy Gross <andy.gross@linaro.org>
> ---
>  arch/arm64/kernel/asm-offsets.c | 1 +
>  arch/arm64/kernel/smccc-call.S  | 1 +
>  include/linux/arm-smccc.h       | 4 +++-
>  3 files changed, 5 insertions(+), 1 deletion(-)

[...]

> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index b5abfda..82d919f 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -63,18 +63,20 @@
>  /**
>   * struct arm_smccc_res - Result from SMC/HVC call
>   * @a0-a3 result values from registers 0 to 3
> + * @a6 Session ID register (optional)
>   */
>  struct arm_smccc_res {
>  	unsigned long a0;
>  	unsigned long a1;
>  	unsigned long a2;
>  	unsigned long a3;
> +	unsigned long a6;
>  };
>  
>  /**
>   * arm_smccc_smc() - make SMC calls
>   * @a0-a7: arguments passed in registers 0 to 7
> - * @res: result values from registers 0 to 3
> + * @res: result values from registers 0 to 3 and optional register 6

AFAICT from reading the SMCCC spec, parameter register 6 is "Unpredictable,
Scratch registers" in return state, so I don't think this is correct.

What am I missing?

Will
Andy Gross Aug. 22, 2016, 2:02 p.m. UTC | #2
On Mon, Aug 22, 2016 at 02:43:14PM +0100, Will Deacon wrote:
> On Sat, Aug 20, 2016 at 12:51:13AM -0500, Andy Gross wrote:
> > This patch adds the SMC Session ID to the results passed back from SMC
> > calls.  The Qualcomm SMC implementation provides for interrupted SMC
> > functions.  When this occurs, the SMC call will return a session ID that
> > is required to be used when resuming the interrupted SMC call.
> > 
> > Signed-off-by: Andy Gross <andy.gross@linaro.org>
> > ---
> >  arch/arm64/kernel/asm-offsets.c | 1 +
> >  arch/arm64/kernel/smccc-call.S  | 1 +
> >  include/linux/arm-smccc.h       | 4 +++-
> >  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> [...]
> 
> > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> > index b5abfda..82d919f 100644
> > --- a/include/linux/arm-smccc.h
> > +++ b/include/linux/arm-smccc.h
> > @@ -63,18 +63,20 @@
> >  /**
> >   * struct arm_smccc_res - Result from SMC/HVC call
> >   * @a0-a3 result values from registers 0 to 3
> > + * @a6 Session ID register (optional)
> >   */
> >  struct arm_smccc_res {
> >  	unsigned long a0;
> >  	unsigned long a1;
> >  	unsigned long a2;
> >  	unsigned long a3;
> > +	unsigned long a6;
> >  };
> >  
> >  /**
> >   * arm_smccc_smc() - make SMC calls
> >   * @a0-a7: arguments passed in registers 0 to 7
> > - * @res: result values from registers 0 to 3
> > + * @res: result values from registers 0 to 3 and optional register 6
> 
> AFAICT from reading the SMCCC spec, parameter register 6 is "Unpredictable,
> Scratch registers" in return state, so I don't think this is correct.
> 
> What am I missing?

In the case of Qualcomm's implementation, they return a value in register 6 that
may or may not be used in subsequent calls.  If I want to leverage the arm_smccc
functions, then I need to extend them to include the optional return value.  The
downside to this is that everyone who uses this is exposed to it.

Regards,

Andy
Bjorn Andersson Aug. 24, 2016, 6:24 p.m. UTC | #3
On Fri 19 Aug 22:51 PDT 2016, Andy Gross wrote:

> This patch adds the SMC Session ID to the results passed back from SMC
> calls.  The Qualcomm SMC implementation provides for interrupted SMC
> functions.  When this occurs, the SMC call will return a session ID that
> is required to be used when resuming the interrupted SMC call.
> 
> Signed-off-by: Andy Gross <andy.gross@linaro.org>

This fixes the spurious remoteproc firmware authentication failures I've
seen lately.

Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> ---
>  arch/arm64/kernel/asm-offsets.c | 1 +
>  arch/arm64/kernel/smccc-call.S  | 1 +
>  include/linux/arm-smccc.h       | 4 +++-
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 05070b7..ff38c58 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -141,6 +141,7 @@ int main(void)
>  #endif
>    DEFINE(ARM_SMCCC_RES_X0_OFFS,	offsetof(struct arm_smccc_res, a0));
>    DEFINE(ARM_SMCCC_RES_X2_OFFS,	offsetof(struct arm_smccc_res, a2));
> +  DEFINE(ARM_SMCCC_RES_X6_OFFS,	offsetof(struct arm_smccc_res, a6));
>    BLANK();
>    DEFINE(HIBERN_PBE_ORIG,	offsetof(struct pbe, orig_address));
>    DEFINE(HIBERN_PBE_ADDR,	offsetof(struct pbe, address));
> diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S
> index ae0496f..278dc9a 100644
> --- a/arch/arm64/kernel/smccc-call.S
> +++ b/arch/arm64/kernel/smccc-call.S
> @@ -20,6 +20,7 @@
>  	ldr	x4, [sp]
>  	stp	x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
>  	stp	x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS]
> +	str	x6, [x4, #ARM_SMCCC_RES_X6_OFFS]
>  	ret
>  	.cfi_endproc
>  	.endm
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index b5abfda..82d919f 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -63,18 +63,20 @@
>  /**
>   * struct arm_smccc_res - Result from SMC/HVC call
>   * @a0-a3 result values from registers 0 to 3
> + * @a6 Session ID register (optional)
>   */
>  struct arm_smccc_res {
>  	unsigned long a0;
>  	unsigned long a1;
>  	unsigned long a2;
>  	unsigned long a3;
> +	unsigned long a6;
>  };
>  
>  /**
>   * arm_smccc_smc() - make SMC calls
>   * @a0-a7: arguments passed in registers 0 to 7
> - * @res: result values from registers 0 to 3
> + * @res: result values from registers 0 to 3 and optional register 6
>   *
>   * This function is used to make SMC calls following SMC Calling Convention.
>   * The content of the supplied param are copied to registers 0 to 7 prior
> -- 
> 1.9.1
>

Patch
diff mbox

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 05070b7..ff38c58 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -141,6 +141,7 @@  int main(void)
 #endif
   DEFINE(ARM_SMCCC_RES_X0_OFFS,	offsetof(struct arm_smccc_res, a0));
   DEFINE(ARM_SMCCC_RES_X2_OFFS,	offsetof(struct arm_smccc_res, a2));
+  DEFINE(ARM_SMCCC_RES_X6_OFFS,	offsetof(struct arm_smccc_res, a6));
   BLANK();
   DEFINE(HIBERN_PBE_ORIG,	offsetof(struct pbe, orig_address));
   DEFINE(HIBERN_PBE_ADDR,	offsetof(struct pbe, address));
diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S
index ae0496f..278dc9a 100644
--- a/arch/arm64/kernel/smccc-call.S
+++ b/arch/arm64/kernel/smccc-call.S
@@ -20,6 +20,7 @@ 
 	ldr	x4, [sp]
 	stp	x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
 	stp	x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS]
+	str	x6, [x4, #ARM_SMCCC_RES_X6_OFFS]
 	ret
 	.cfi_endproc
 	.endm
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index b5abfda..82d919f 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -63,18 +63,20 @@ 
 /**
  * struct arm_smccc_res - Result from SMC/HVC call
  * @a0-a3 result values from registers 0 to 3
+ * @a6 Session ID register (optional)
  */
 struct arm_smccc_res {
 	unsigned long a0;
 	unsigned long a1;
 	unsigned long a2;
 	unsigned long a3;
+	unsigned long a6;
 };
 
 /**
  * arm_smccc_smc() - make SMC calls
  * @a0-a7: arguments passed in registers 0 to 7
- * @res: result values from registers 0 to 3
+ * @res: result values from registers 0 to 3 and optional register 6
  *
  * This function is used to make SMC calls following SMC Calling Convention.
  * The content of the supplied param are copied to registers 0 to 7 prior