linux-kernel - Re: [PATCH v8 19/28] KVM: arm64: Support unaligned fixmap in the pKVM hyp

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Message-ID: <aR7lggObvo-2Yrg5@google.com>
Date: Thu, 20 Nov 2025 09:55:14 +0000
From: Vincent Donnefort <vdonnefort@...gle.com>
To: Marc Zyngier <maz@...nel.org>
Cc: rostedt@...dmis.org, mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com, linux-trace-kernel@...r.kernel.org,
	oliver.upton@...ux.dev, joey.gouly@....com, suzuki.poulose@....com,
	yuzenghui@...wei.com, kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, jstultz@...gle.com,
	qperret@...gle.com, will@...nel.org, aneesh.kumar@...nel.org,
	kernel-team@...roid.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 19/28] KVM: arm64: Support unaligned fixmap in the
 pKVM hyp

Hi Marc,

Thanks for having a look at the series.


On Wed, Nov 19, 2025 at 03:38:32PM +0000, Marc Zyngier wrote:
> On Fri, 07 Nov 2025 09:38:31 +0000,
> Vincent Donnefort <vdonnefort@...gle.com> wrote:
> > 
> > Return the fixmap VA with the page offset, instead of the page base
> > address. This allows to use hyp_fixmap_map() seamlessly regardless of
> > the address alignment.
> > 
> > Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>
> > 
> > diff --git a/arch/arm64/kvm/hyp/nvhe/mm.c b/arch/arm64/kvm/hyp/nvhe/mm.c
> > index ae8391baebc3..75014dc7d82e 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/mm.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/mm.c
> > @@ -239,7 +239,7 @@ static void *fixmap_map_slot(struct hyp_fixmap_slot *slot, phys_addr_t phys)
> >  	WRITE_ONCE(*ptep, pte);
> >  	dsb(ishst);
> >  
> > -	return (void *)slot->addr;
> > +	return (void *)slot->addr + offset_in_page(phys);
> >  }
> >  
> >  void *hyp_fixmap_map(phys_addr_t phys)
> 
> This looks slightly odd. fixmap_map_slot() should return *a slot*, not
> something in it. Can't hyp_fixmap_map() do that instead?

That was fixing hyp_fixblock_map() at the same time. I will move the
offset_in_page() in both callers.

> 
> Thanks,
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.