From: Quentin Perret <qperret@google.com>
To: Marc Zyngier <maz@kernel.org>
Cc: will@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com,
catalin.marinas@arm.com, suzuki.poulose@arm.com,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, kernel-team@android.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/7] KVM: arm64: Remove list_head from hyp_page
Date: Wed, 2 Jun 2021 09:23:33 +0000 [thread overview]
Message-ID: <YLdOFUPjgCK33Vd5@google.com> (raw)
In-Reply-To: <87fsy11nz6.wl-maz@kernel.org>
On Tuesday 01 Jun 2021 at 18:41:49 (+0100), Marc Zyngier wrote:
> On Tue, 01 Jun 2021 16:48:06 +0100,
> Quentin Perret <qperret@google.com> wrote:
> >
> > On Tuesday 01 Jun 2021 at 15:38:22 (+0100), Marc Zyngier wrote:
> > > On Thu, 27 May 2021 13:51:30 +0100,
> > > Quentin Perret <qperret@google.com> wrote:
> > > > +/*
> > > > + * Pages that are available for allocation are tracked in free-lists, so we use
> > > > + * the pages themselves to store the list nodes to avoid wasting space. As the
> > > > + * allocator always returns zeroed pages (which are zeroed on the hyp_put_page()
> > > > + * path to optimize allocation speed), we also need to clean-up the list node in
> > > > + * each page when we take it out of the list.
> > > > + */
> > > > +static inline void page_remove_from_list(struct hyp_page *p)
> > > > +{
> > > > + struct list_head *node = (struct list_head *)hyp_page_to_virt(p);
> > >
> > > Nit: How about changing hyp_page_to_virt() so that it returns a
> > > convenient 'void *', and get rid of the ugly casts?
> >
> > It should already return void *, but I kind of liked the explicit cast
> > here for documentation purpose. We're turning a 'random' piece of unused
> > memory into a typed object, so that felt like a useful annotation. Happy
> > to get rid of it though.
>
> My expectations were that using hyp_page_to_virt() already serves as a
> pretty big warning that we're doing something unusual.
>
> I guess that if we want to be really careful about those, we should
> then be consistent and make it return a uintptr_t (or unsigned long)
> instead, actively making use of the cast, consistently, everywhere.
Right, so I'd prefer keeping it void * for consistency with the EL1
equivalent -- much of this aims to be API compatible with the Linux
stuff. I'll get rid of the cast and post a v2 shortly.
Cheers,
Quentin
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next prev parent reply other threads:[~2021-06-02 9:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 12:51 [PATCH 0/7] KVM: arm64: Reduce hyp_vmemmap overhead Quentin Perret
2021-05-27 12:51 ` [PATCH 1/7] KVM: arm64: Move hyp_pool locking out of refcount helpers Quentin Perret
2021-06-01 12:02 ` Marc Zyngier
2021-06-01 13:31 ` Quentin Perret
2021-05-27 12:51 ` [PATCH 2/7] KVM: arm64: Use refcount at hyp to check page availability Quentin Perret
2021-05-27 12:51 ` [PATCH 3/7] KVM: arm64: Remove list_head from hyp_page Quentin Perret
2021-06-01 14:38 ` Marc Zyngier
2021-06-01 15:48 ` Quentin Perret
2021-06-01 17:41 ` Marc Zyngier
2021-06-02 9:23 ` Quentin Perret [this message]
2021-05-27 12:51 ` [PATCH 4/7] KVM: arm64: Unify MMIO and mem host stage-2 pools Quentin Perret
2021-05-27 12:51 ` [PATCH 5/7] KVM: arm64: Remove hyp_pool pointer from struct hyp_page Quentin Perret
2021-06-01 15:00 ` Marc Zyngier
2021-05-27 12:51 ` [PATCH 6/7] KVM: arm64: Use less bits for hyp_page order Quentin Perret
2021-05-27 12:51 ` [PATCH 7/7] KVM: arm64: Use less bits for hyp_page refcount Quentin Perret
2021-06-01 15:21 ` Marc Zyngier
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