From: Catalin Marinas <catalin.marinas@arm.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Marc Zyngier <maz@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Steve Capper <steve.capper@arm.com>
Subject: Re: [RFC PATCH] arm64: mm: limit linear region to 51 bits for KVM in nVHE mode
Date: Thu, 26 Aug 2021 13:16:24 +0100 [thread overview]
Message-ID: <20210826121623.GB30910@arm.com> (raw)
In-Reply-To: <CAMj1kXHKvUng_z5Gfd0bsFgbnpVPA-JjPLCRTa=87yVa4j7kHA@mail.gmail.com>
On Tue, Aug 24, 2021 at 02:56:22PM +0200, Ard Biesheuvel wrote:
> On Tue, 24 Aug 2021 at 12:59, Will Deacon <will@kernel.org> wrote:
> > On Tue, Aug 10, 2021 at 06:12:44PM +0200, Ard Biesheuvel wrote:
> > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > > index 8490ed2917ff..542dad13e2fc 100644
> > > --- a/arch/arm64/mm/init.c
> > > +++ b/arch/arm64/mm/init.c
> > > @@ -282,7 +282,21 @@ static void __init fdt_enforce_memory_region(void)
> > >
> > > void __init arm64_memblock_init(void)
> > > {
> > > - const s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
> > > + s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
> > > +
> > > + /*
> > > + * Corner case: 52-bit VA capable systems running KVM in nVHE mode may
> > > + * be limited in their ability to support a linear map that exceeds 51
> > > + * bits of VA space, depending on the placement of the ID map. Given
> > > + * that the placement of the ID map may be randomized, let's simply
> > > + * limit the kernel's linear map to 51 bits as well if we detect this
> > > + * configuration.
> > > + */
> > > + if (IS_ENABLED(CONFIG_KVM) && vabits_actual == 52 &&
> > > + !is_kernel_in_hyp_mode()) {
> > > + pr_info("Capping linear region to 51 bits for KVM in nVHE mode on LVA capable hardware.\n");
> > > + linear_region_size = BIT(51);
> > > + }
> >
> > Slight nit, but to avoid having to think about PAGE_END I think this would
> > be a little clearer as:
> >
> > if (IS_ENABLED(CONFIG_KVM) && !is_kernel_in_hyp_mode())
> > linear_region_size = min_t(u64, linear_region_size, BIT(51));
> >
>
> Fair enough.
Ard, do you plan to post a new version? I can make the change myself
locally as well.
--
Catalin
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next prev parent reply other threads:[~2021-08-26 12:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-10 16:12 [RFC PATCH] arm64: mm: limit linear region to 51 bits for KVM in nVHE mode Ard Biesheuvel
2021-08-24 10:59 ` Will Deacon
2021-08-24 12:56 ` Ard Biesheuvel
2021-08-26 12:16 ` Catalin Marinas [this message]
2021-08-26 12:23 ` Ard Biesheuvel
2021-08-26 13:31 ` Catalin Marinas
2021-08-26 16:34 ` Ard Biesheuvel
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