linux-kernel - Re: [PATCH] RISC-V: KVM: Delegate illegal instruction fault

Open Source and information security mailing list archives

Message-ID: <1d9ad2a8-6ab5-4f5e-b514-4a902392e074@rivosinc.com>
Date: Mon, 23 Jun 2025 10:04:45 +0200
From: Clément Léger <cleger@...osinc.com>
To: Radim Krčmář <rkrcmar@...tanamicro.com>,
 Xu Lu <luxu.kernel@...edance.com>, anup@...infault.org,
 atish.patra@...ux.dev, paul.walmsley@...ive.com, palmer@...belt.com,
 aou@...s.berkeley.edu, alex@...ti.fr
Cc: kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-riscv <linux-riscv-bounces@...ts.infradead.org>
Subject: Re: [PATCH] RISC-V: KVM: Delegate illegal instruction fault

On 20/06/2025 14:04, Radim Krčmář wrote:
> 2025-06-20T17:17:20+08:00, Xu Lu <luxu.kernel@...edance.com>:
>> Delegate illegal instruction fault to VS mode in default to avoid such
>> exceptions being trapped to HS and redirected back to VS.
>>
>> Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
>> ---
>> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
>> @@ -48,6 +48,7 @@
>> +					 BIT(EXC_INST_ILLEGAL)    | \
> 
> You should also remove the dead code in kvm_riscv_vcpu_exit.
> 
> And why not delegate the others as well?
> (EXC_LOAD_MISALIGNED, EXC_STORE_MISALIGNED, EXC_LOAD_ACCESS,
>  EXC_STORE_ACCESS, and EXC_INST_ACCESS.)

Currently, OpenSBI does not delegate misaligned exception by default and
handles misaligned access by itself, this is (partially) why we added
the FWFT SBI extension to request such delegation. Since some supervisor
software expect that default, they do not have code to handle misaligned
accesses emulation. So they should not be delegated by default.

Thanks,

Clément

> 
> Thanks.
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives