linux-kernel - Re: [PATCH 1/3] KVM: riscv: selftests: Add stval to exception handling

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Message-ID: <20250425-dc44cb547ab5e2f994c94e80@orel>
Date: Fri, 25 Apr 2025 15:50:27 +0200
From: Andrew Jones <ajones@...tanamicro.com>
To: Atish Patra <atishp@...osinc.com>
Cc: Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>, 
	Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Alexandre Ghiti <alex@...ti.fr>, kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] KVM: riscv: selftests: Add stval to exception
 handling

On Mon, Mar 24, 2025 at 05:40:29PM -0700, Atish Patra wrote:
> Save stval during exception handling so that it can be decoded to
> figure out the details of exception type.
> 
> Signed-off-by: Atish Patra <atishp@...osinc.com>
> ---
>  tools/testing/selftests/kvm/include/riscv/processor.h | 1 +
>  tools/testing/selftests/kvm/lib/riscv/handlers.S      | 2 ++
>  2 files changed, 3 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/riscv/processor.h b/tools/testing/selftests/kvm/include/riscv/processor.h
> index 5f389166338c..f4a7d64fbe9a 100644
> --- a/tools/testing/selftests/kvm/include/riscv/processor.h
> +++ b/tools/testing/selftests/kvm/include/riscv/processor.h
> @@ -95,6 +95,7 @@ struct ex_regs {
>  	unsigned long epc;
>  	unsigned long status;
>  	unsigned long cause;
> +	unsigned long stval;
>  };
>  
>  #define NR_VECTORS  2
> diff --git a/tools/testing/selftests/kvm/lib/riscv/handlers.S b/tools/testing/selftests/kvm/lib/riscv/handlers.S
> index aa0abd3f35bb..2884c1e8939b 100644
> --- a/tools/testing/selftests/kvm/lib/riscv/handlers.S
> +++ b/tools/testing/selftests/kvm/lib/riscv/handlers.S
> @@ -45,9 +45,11 @@
>  	csrr  s0, CSR_SEPC
>  	csrr  s1, CSR_SSTATUS
>  	csrr  s2, CSR_SCAUSE
> +	csrr  s3, CSR_STVAL
>  	sd    s0, 248(sp)
>  	sd    s1, 256(sp)
>  	sd    s2, 264(sp)
> +	sd    s3, 272(sp)

We can't add stval without also changing how much stack we allocate at the
top of this macro, but since we need to keep sp 16-byte aligned in order
to call C code (route_exception()) we'll need to decrement -8*36, not
-8*35. Or, we could just switch struct ex_regs to be the kernel's struct
pt_regs which has 36 unsigned longs. The 'badaddr' member is for stval and
the additional long is orig_a0.

>  .endm
>  
>  .macro restore_context

I guess we should restore stval too.

Thanks,
drew

> 
> -- 
> 2.43.0
> 
> 
> -- 
> kvm-riscv mailing list
> kvm-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kvm-riscv

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