Re: [PATCH v4 2/4] RISC-V: KVM: Detect and expose supported HGATP G-stage modes

From: "Radim Krčmář" <radim.krcmar@oss.qualcomm.com>
To: <fangyu.yu@linux.alibaba.com>, <pbonzini@redhat.com>,
	<corbet@lwn.net>, <anup@brainfault.org>, <atish.patra@linux.dev>,
	<pjw@kernel.org>, <palmer@dabbelt.com>, <aou@eecs.berkeley.edu>,
	<alex@ghiti.fr>
Cc: <guoren@kernel.org>, <ajones@ventanamicro.com>,
	<rkrcmar@ventanamicro.com>, <andrew.jones@oss.qualcomm.com>,
	<linux-doc@vger.kernel.org>, <kvm@vger.kernel.org>,
	<kvm-riscv@lists.infradead.org>,
	<linux-riscv@lists.infradead.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 2/4] RISC-V: KVM: Detect and expose supported HGATP G-stage modes
Date: Mon, 02 Feb 2026 19:14:21 +0000	[thread overview]
Message-ID: <DG4PS6NRRUC1.1FL8WBJVEEM4D@oss.qualcomm.com> (raw)
In-Reply-To: <20260202140716.34323-3-fangyu.yu@linux.alibaba.com>

2026-02-02T22:07:14+08:00, <fangyu.yu@linux.alibaba.com>:
> From: Fangyu Yu <fangyu.yu@linux.alibaba.com>
>
> Extend kvm_riscv_gstage_mode_detect() to probe all HGATP.MODE values
> supported by the host and record them in a bitmask. Keep tracking the
> maximum supported G-stage page table level for existing internal users.
>
> Also provide lightweight helpers to retrieve the supported-mode bitmask
> and validate a requested HGATP.MODE against it.
>
> Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
> ---
> diff --git a/arch/riscv/include/asm/kvm_gstage.h b/arch/riscv/include/asm/kvm_gstage.h
> @@ -75,4 +76,40 @@ void kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end
> +enum kvm_riscv_hgatp_mode_bit {
> +	HGATP_MODE_SV39X4_BIT = 0,
> +	HGATP_MODE_SV48X4_BIT = 1,
> +	HGATP_MODE_SV57X4_BIT = 2,

I think it's a bit awkward to pass 9 when selecting the hgatp mode, but
then look for bit 0 when detecting it...
Why not to use the RVI defined values for this UABI as well?

There are only 16 possible hgatp.mode values, so we're fine storing them
in a bitmap even on RV32.

Thanks.

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