linux-kernel - Re: [PATCH v8 13/14] RISC-V: KVM: add support for FWFT SBI extension

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Message-Id: <DA3K95ZYJ52S.1K6O3LN6WEI0N@ventanamicro.com>
Date: Fri, 23 May 2025 15:05:54 +0200
From: Radim Krčmář <rkrcmar@...tanamicro.com>
To: Clément Léger <cleger@...osinc.com>, "Paul
 Walmsley" <paul.walmsley@...ive.com>, "Palmer Dabbelt"
 <palmer@...belt.com>, "Anup Patel" <anup@...infault.org>, "Atish Patra"
 <atishp@...shpatra.org>, "Shuah Khan" <shuah@...nel.org>, "Jonathan Corbet"
 <corbet@....net>, <linux-riscv@...ts.infradead.org>,
 <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
 <kvm@...r.kernel.org>, <kvm-riscv@...ts.infradead.org>,
 <linux-kselftest@...r.kernel.org>
Cc: "Samuel Holland" <samuel.holland@...ive.com>, "Andrew Jones"
 <ajones@...tanamicro.com>, "Deepak Gupta" <debug@...osinc.com>, "Charlie
 Jenkins" <charlie@...osinc.com>, "Atish Patra" <atishp@...osinc.com>,
 "linux-riscv" <linux-riscv-bounces@...ts.infradead.org>
Subject: Re: [PATCH v8 13/14] RISC-V: KVM: add support for FWFT SBI
 extension

2025-05-23T12:19:30+02:00, Clément Léger <cleger@...osinc.com>:
> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
> +static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
> +	SBI_FWFT_MISALIGNED_EXC_DELEG,
> +	SBI_FWFT_LANDING_PAD,
> +	SBI_FWFT_SHADOW_STACK,
> +	SBI_FWFT_DOUBLE_TRAP,
> +	SBI_FWFT_PTE_AD_HW_UPDATING,
> +	SBI_FWFT_POINTER_MASKING_PMLEN,
> +};

How will userspace control which subset of these features is allowed in
the guest?

(We can reuse the KVM SBI extension interface if we don't want to add a
 FWFT specific ONE_REG.)

Thanks.