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

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Message-ID: <20251124-4ecf1b6b91b8f0688b762698@orel>
Date: Mon, 24 Nov 2025 09:27:57 -0600
From: Andrew Jones <ajones@...tanamicro.com>
To: Guo Ren <guoren@...nel.org>
Cc: fangyu.yu@...ux.alibaba.com, anup@...infault.org, 
	atish.patra@...ux.dev, pjw@...nel.org, palmer@...belt.com, aou@...s.berkeley.edu, 
	alex@...ti.fr, kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RISC-V: KVM: Allow to downgrade HGATP mode via SATP mode

On Sun, Nov 23, 2025 at 10:33:19AM +0800, Guo Ren wrote:
> On Sat, Nov 22, 2025 at 3:50 PM <fangyu.yu@...ux.alibaba.com> wrote:
> >
> > From: Fangyu Yu <fangyu.yu@...ux.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