From: Scott Wood <scottwood@freescale•com>
To: Alexander Graf <agraf@suse•de>
Cc: "Wood Scott-B07421" <B07421@freescale•com>,
"Gleb Natapov" <gleb@redhat•com>,
"kvm@vger•kernel.org list" <kvm@vger•kernel.org>,
"kvm-ppc@vger•kernel.org" <kvm-ppc@vger•kernel.org>,
"“tiejun.chen”" <tiejun.chen@windriver•com>,
"Bhushan Bharat-R65777" <R65777@freescale•com>,
"Paolo Bonzini" <pbonzini@redhat•com>,
linuxppc-dev@lists•ozlabs.org
Subject: Re: [PATCH 2/2] kvm: powerpc: set cache coherency only for kernel managed pages
Date: Wed, 24 Jul 2013 15:32:49 -0500 [thread overview]
Message-ID: <1374697969.15592.67@snotra> (raw)
In-Reply-To: <03EEFDFE-4603-44FC-8449-2450607F2864@suse.de> (from agraf@suse.de on Wed Jul 24 04:39:59 2013)
On 07/24/2013 04:39:59 AM, Alexander Graf wrote:
>=20
> On 24.07.2013, at 11:35, Gleb Natapov wrote:
>=20
> > On Wed, Jul 24, 2013 at 11:21:11AM +0200, Alexander Graf wrote:
> >>> Are not we going to use page_is_ram() from =20
> e500_shadow_mas2_attrib() as Scott commented?
> >>
> >> rWhy aren't we using page_is_ram() in kvm_is_mmio_pfn()?
> >>
> >>
> > Because it is much slower and, IIRC, actually used to build pfn map =20
> that allow
> > us to check quickly for valid pfn.
>=20
> Then why should we use page_is_ram()? :)
>=20
> I really don't want the e500 code to diverge too much from what the =20
> rest of the kvm code is doing.
I don't understand "actually used to build pfn map...". What code is =20
this? I don't see any calls to page_is_ram() in the KVM code, or in =20
generic mm code. Is this a statement about what x86 does?
On PPC page_is_ram() is only called (AFAICT) for determining what =20
attributes to set on mmaps. We want to be sure that KVM always makes =20
the same decision. While pfn_valid() seems like it should be =20
equivalent, it's not obvious from the PPC code that it is.
If pfn_valid() is better, why is that not used for mmap? Why are there =20
two different names for the same thing?
-Scott=
next parent reply other threads:[~2013-07-24 20:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <03EEFDFE-4603-44FC-8449-2450607F2864@suse.de>
2013-07-24 20:32 ` Scott Wood [this message]
2013-07-25 8:50 ` [PATCH 2/2] kvm: powerpc: set cache coherency only for kernel managed pages Gleb Natapov
2013-07-25 16:07 ` Alexander Graf
2013-07-25 16:14 ` Gleb Natapov
2013-07-26 22:27 ` Scott Wood
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