From: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@globallogic.com>
To: Ian Campbell <ian.campbell@citrix.com>
Cc: Keir Fraser <keir@xen.org>,
Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
xen-devel <xen-devel@lists.xen.org>,
Stefano Stabellini <stefano.stabellini@citrix.com>,
Jan Beulich <jbeulich@suse.com>
Subject: Re: Question about mapping between domains
Date: Tue, 14 Jul 2015 18:31:56 +0300 [thread overview]
Message-ID: <CAN58jitB6NFghT7kQ7QbuZydQwswtzAVzc5_FM3xj2i9BZgjXA@mail.gmail.com> (raw)
In-Reply-To: <1436778275.7019.32.camel@citrix.com>
Hi, Ian. Thank You for the responce.
Currently have 3 kernels: Thin Dom0 (privileged), DomD (privileged
driver domain),
DomU (not privileged)
On Mon, Jul 13, 2015 at 12:04 PM, Ian Campbell <ian.campbell@citrix.com> wrote:
> The way we deal with this elsewhere in the kernel is that we only ever
> do grant mappings over ballooned out pages, which are allocated via
> gnttab_alloc_pages. That way when they are unmapped the page is expected
> to be entry and no backing mfn is lost. The page can then subsequently
> be ballooned back in as normal.
We can not use this case because our DRM driver has already allocated memory
which will be mapped later.
> There is an additional quirk for a 1:1 mapped dom0 which is that we
> don't actually decrease reservation when ballooning, but keep the 1:1
> mfn in anticipation of ballooning it back in later.
Could You please tell me a bit more information about this quirk. How this quirk
can be enabled?
> If you can't arrange to use already ballooned buffers for your DMA
> buffer then you will need to manually balloon it out before and balloon
> it back in later.
This is my case. I'll try to to this.
> You may also want to extend the dom0 1:1 quirk described above to your
> 1:1 mapped domD.
Necessarily I will do this.
> If you have sufficient control over/knowledge of the domD IPA space then
> you could also try and arrange that the region used for these mappings
> does not correspond to any real RAM in the guest (i.e. stick it in an
> MMIO hole). That depends on you never needing to find an associated
> struct page though, which will depend on your use case.
Necessarily I will do this.
> Ian.
>
Oleksandr Dmytryshyn | Product Engineering and Development
GlobalLogic
M +38.067.382.2525
www.globallogic.com
http://www.globallogic.com/email_disclaimer.txt
next prev parent reply other threads:[~2015-07-14 15:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-09 13:31 Question about mapping between domains Oleksandr Dmytryshyn
2015-07-13 9:04 ` Ian Campbell
2015-07-14 15:31 ` Oleksandr Dmytryshyn [this message]
2015-07-14 15:41 ` Oleksandr Dmytryshyn
2015-07-14 15:50 ` Ian Campbell
2015-07-15 8:28 ` Oleksandr Dmytryshyn
2015-07-15 11:51 ` Stefano Stabellini
2015-07-15 12:00 ` Ian Campbell
2015-07-14 15:49 ` Ian Campbell
2015-07-17 7:43 ` Oleksandr Dmytryshyn
2015-07-17 8:59 ` Ian Campbell
2015-07-22 12:07 ` Oleksandr Dmytryshyn
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