From: Keir Fraser <keir.fraser@eu.citrix.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Avi Kivity <avi@qumranet.com>, Ingo Molnar <mingo@elte.hu>,
Xen Devel <xen-devel@lists.xensource.com>,
Andi Kleen <andi@firstfloor.org>, <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [Xen-devel] Re: [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag for IO mappings
Date: Tue, 09 Sep 2008 17:05:00 +0100 [thread overview]
Message-ID: <C4EC5D3C.26EF1%keir.fraser@eu.citrix.com> (raw)
In-Reply-To: <48C69AB6.20500@goop.org>
On 9/9/08 16:48, "Jeremy Fitzhardinge" <jeremy@goop.org> wrote:
> Keir Fraser wrote:
>> That's basically what our _PAGE_IO flag (in our old Linux patchset) means.
>> We use it to cause pte_pfn() to return an invalid pfn and hence avoid
>> reference counting that way. Since kernel mappings are never reference
>> counted (I think?) perhaps we could use _PAGE_SPECIAL even if it is
>> restricted to use on user mappings.
>
> Well, _PAGE_IOMAP's most important semantic from Xen's perspective is
> that the frame number is considered to already be an MFN and so isn't
> converted. It may be that _PAGE_SPECIAL is also useful for its "no
> refcount" properties, but we could set both in that case.
Oh, yes, our _PAGE_IO has the same meaning.
-- Keir
WARNING: multiple messages have this Message-ID (diff)
From: Keir Fraser <keir.fraser@eu.citrix.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Xen Devel <xen-devel@lists.xensource.com>,
linux-kernel@vger.kernel.org, Avi Kivity <avi@qumranet.com>,
Andi Kleen <andi@firstfloor.org>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@elte.hu>
Subject: Re: Re: [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag for IO mappings
Date: Tue, 09 Sep 2008 17:05:00 +0100 [thread overview]
Message-ID: <C4EC5D3C.26EF1%keir.fraser@eu.citrix.com> (raw)
In-Reply-To: <48C69AB6.20500@goop.org>
On 9/9/08 16:48, "Jeremy Fitzhardinge" <jeremy@goop.org> wrote:
> Keir Fraser wrote:
>> That's basically what our _PAGE_IO flag (in our old Linux patchset) means.
>> We use it to cause pte_pfn() to return an invalid pfn and hence avoid
>> reference counting that way. Since kernel mappings are never reference
>> counted (I think?) perhaps we could use _PAGE_SPECIAL even if it is
>> restricted to use on user mappings.
>
> Well, _PAGE_IOMAP's most important semantic from Xen's perspective is
> that the frame number is considered to already be an MFN and so isn't
> converted. It may be that _PAGE_SPECIAL is also useful for its "no
> refcount" properties, but we could set both in that case.
Oh, yes, our _PAGE_IO has the same meaning.
-- Keir
next prev parent reply other threads:[~2008-09-09 16:05 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-07 22:21 [PATCH 0 of 7] x86: lay groundwork for Xen domain 0 support Jeremy Fitzhardinge
2008-09-07 22:21 ` [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag for IO mappings Jeremy Fitzhardinge
2008-09-09 13:32 ` Avi Kivity
2008-09-09 13:32 ` Avi Kivity
2008-09-09 14:47 ` Jeremy Fitzhardinge
2008-09-09 14:47 ` Jeremy Fitzhardinge
2008-09-09 14:56 ` Avi Kivity
2008-09-09 14:56 ` Avi Kivity
2008-09-09 15:29 ` [Xen-devel] " Keir Fraser
2008-09-09 15:29 ` Keir Fraser
2008-09-09 15:48 ` [Xen-devel] " Jeremy Fitzhardinge
2008-09-09 15:48 ` Jeremy Fitzhardinge
2008-09-09 16:05 ` Keir Fraser [this message]
2008-09-09 16:05 ` Keir Fraser
2008-09-10 9:55 ` [Xen-devel] " Avi Kivity
2008-09-10 9:55 ` Avi Kivity
2008-09-10 16:38 ` [Xen-devel] " Jeremy Fitzhardinge
2008-09-10 16:38 ` Jeremy Fitzhardinge
2008-09-10 16:55 ` [Xen-devel] " Nick Piggin
2008-09-10 17:27 ` Jeremy Fitzhardinge
2008-09-07 22:21 ` [PATCH 2 of 7] x86: remove duplicate early_ioremap declarations Jeremy Fitzhardinge
2008-09-07 22:21 ` Jeremy Fitzhardinge
2008-09-07 22:21 ` [PATCH 3 of 7] x86: add early_memremap() Jeremy Fitzhardinge
2008-09-07 22:21 ` Jeremy Fitzhardinge
2008-09-07 22:21 ` [PATCH 4 of 7] x86: use early_memremap() in setup.c Jeremy Fitzhardinge
2008-09-07 22:21 ` [PATCH 5 of 7] x86-64: don't check for map replacement Jeremy Fitzhardinge
2008-09-07 22:21 ` [PATCH 6 of 7] x86: use early_ioremap in __acpi_map_table Jeremy Fitzhardinge
2008-09-07 23:44 ` Andi Kleen
2008-09-08 0:03 ` Jeremy Fitzhardinge
2008-09-08 0:03 ` Jeremy Fitzhardinge
2008-09-08 14:26 ` Ingo Molnar
2008-09-08 14:26 ` Ingo Molnar
2008-09-08 16:29 ` Jeremy Fitzhardinge
2008-09-08 16:29 ` Jeremy Fitzhardinge
2008-09-08 19:41 ` Jeremy Fitzhardinge
2008-09-08 19:41 ` Jeremy Fitzhardinge
2008-09-10 11:55 ` Ingo Molnar
2008-09-10 16:49 ` Jeremy Fitzhardinge
2008-09-11 7:33 ` Ingo Molnar
2008-09-11 18:36 ` Jeremy Fitzhardinge
2008-09-11 18:56 ` Ingo Molnar
2008-09-11 20:34 ` Yinghai Lu
2008-09-11 21:07 ` Jeremy Fitzhardinge
2008-09-12 9:49 ` Ingo Molnar
2008-09-12 17:31 ` Yinghai Lu
[not found] ` <20080911125748.GA14698@elte.hu>
2008-09-11 21:33 ` [PATCH] acpi: remove final __acpi_map_table mapping before setting acpi_gbl_permanent_mmap Jeremy Fitzhardinge
2008-09-07 22:21 ` [PATCH 7 of 7] x86: always explicitly map acpi memory Jeremy Fitzhardinge
2008-09-07 23:35 ` [Xen-devel] " Yinghai Lu
2008-09-07 23:35 ` Yinghai Lu
2008-09-08 0:02 ` [Xen-devel] " Jeremy Fitzhardinge
2008-09-08 0:02 ` Jeremy Fitzhardinge
2008-09-08 0:14 ` [Xen-devel] " Yinghai Lu
2008-09-08 0:14 ` Yinghai Lu
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