[PATCH] xen/arm32: SPSR_hyp/SPSR

[PATCH] xen/arm32: SPSR_hyp/SPSR

[Stefano Stabellini]

SPSR_hyp is not meant to be accessed from Hyp mode (EL2); accesses
trigger UNPREDICTABLE behaviour. Xen should read/write SPSR instead.

This fixes booting Xen/arm32 on QEMU.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
---
 xen/arch/arm/arm32/entry.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
index f2f1bc7a31..4e421109db 100644
--- a/xen/arch/arm/arm32/entry.S
+++ b/xen/arch/arm/arm32/entry.S
@@ -170,7 +170,7 @@ ENDPROC(prepare_context_from_guest)
         mrc     CP32(r11, HSR)                 /* Save exception syndrome */
         str     r11, [sp, #UREGS_hsr]
 
-        mrs     r11, SPSR_hyp
+        mrs     r11, SPSR
         str     r11, [sp, #UREGS_cpsr]
 
         /*
@@ -395,7 +395,7 @@ return_to_hypervisor:
         ldr r11, [sp, #UREGS_pc]
         msr ELR_hyp, r11
         ldr r11, [sp, #UREGS_cpsr]
-        msr SPSR_hyp, r11
+        msr SPSR, r11
 #ifdef CONFIG_ARM32_HARDEN_BRANCH_PREDICTOR
         /*
          * Hardening branch predictor may require to setup a different
-- 
2.17.1

Re: [PATCH] xen/arm32: SPSR_hyp/SPSR

[Julien Grall]

Hi Stefano,

On 09/06/2021 18:43, Stefano Stabellini wrote:
> SPSR_hyp is not meant to be accessed from Hyp mode (EL2); accesses
> trigger UNPREDICTABLE behaviour. Xen should read/write SPSR instead.

Please provide a reference to the spec. This helps reviewer and/or 
future developper to figure out quickly where this comes from.

> 
> This fixes booting Xen/arm32 on QEMU.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>

With the reference added:

Reviewed-by: Julien Grall <jgrall@amazon.com>

Cheers,

-- 
Julien Grall

Re: [PATCH] xen/arm32: SPSR_hyp/SPSR

[Edgar E. Iglesias]

On Wed, Jun 09, 2021 at 06:53:02PM +0100, Julien Grall wrote:
> Hi Stefano,
> 
> On 09/06/2021 18:43, Stefano Stabellini wrote:
> > SPSR_hyp is not meant to be accessed from Hyp mode (EL2); accesses
> > trigger UNPREDICTABLE behaviour. Xen should read/write SPSR instead.
> 
> Please provide a reference to the spec. This helps reviewer and/or future
> developper to figure out quickly where this comes from.
> 
> > 
> > This fixes booting Xen/arm32 on QEMU.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
> 
> With the reference added:
> 
> Reviewed-by: Julien Grall <jgrall@amazon.com>

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>

Cheers,
Edgar

Re: [PATCH] xen/arm32: SPSR_hyp/SPSR

[Stefano Stabellini]

On Wed, 9 Jun 2021, Julien Grall wrote:
> Hi Stefano,
> 
> On 09/06/2021 18:43, Stefano Stabellini wrote:
> > SPSR_hyp is not meant to be accessed from Hyp mode (EL2); accesses
> > trigger UNPREDICTABLE behaviour. Xen should read/write SPSR instead.
> 
> Please provide a reference to the spec. This helps reviewer and/or future
> developper to figure out quickly where this comes from.
> 
> > 
> > This fixes booting Xen/arm32 on QEMU.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
> 
> With the reference added:
> 
> Reviewed-by: Julien Grall <jgrall@amazon.com>

Thanks!

I added: ARM DDI 0487D.b page G8-5993 and committed it