Re: [PATCH] RISC-V: KVM: Allow to downgrade HGATP mode via SATP mode

From: Andrew Jones <ajones@ventanamicro.com>
To: Guo Ren <guoren@kernel.org>
Cc: fangyu.yu@linux.alibaba.com, anup@brainfault.org,
	 atish.patra@linux.dev, pjw@kernel.org, palmer@dabbelt.com,
	aou@eecs.berkeley.edu,  alex@ghiti.fr, kvm@vger.kernel.org,
	kvm-riscv@lists.infradead.org,  linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] RISC-V: KVM: Allow to downgrade HGATP mode via SATP mode
Date: Mon, 24 Nov 2025 09:27:57 -0600	[thread overview]
Message-ID: <20251124-4ecf1b6b91b8f0688b762698@orel> (raw)
In-Reply-To: <CAJF2gTTRBFTnu2pA5rh16EWLvF_Wo=+vpZMUK9roDkDPes4Fpg@mail.gmail.com>

On Sun, Nov 23, 2025 at 10:33:19AM +0800, Guo Ren wrote:
> On Sat, Nov 22, 2025 at 3:50 PM <fangyu.yu@linux.alibaba.com> wrote:
> >
> > From: Fangyu Yu <fangyu.yu@linux.alibaba.com>
> >
> > Currently, HGATP mode uses the maximum value detected by the hardware
> > but often such a wide GPA is unnecessary, just as a host sometimes
> > doesn't need sv57.
> > It's likely that no additional parameters (like no5lvl and no4lvl) are
> > needed, aligning HGATP mode to SATP mode should meet the requirements
> > of most scenarios.
> Yes, no5/4lvl is not clear about satp or hgatp. So, covering HGPATP is
> reasonable.

The documentation should be improved, but I don't think we want to state
that these parameters apply to both s- and g-stage. If we need parameters
to dictate KVM behavior (g-stage management), then we should add KVM
module parameters.

Thanks,
drew

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