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From: Julien Grall <julien.grall@citrix.com>
To: Jan Beulich <JBeulich@suse.com>,
	Tamas K Lengyel <tklengyel@sec.in.tum.de>
Cc: "wei.liu2@citrix.com" <wei.liu2@citrix.com>,
	Ian Campbell <ian.campbell@citrix.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Julien Grall <julien.grall@linaro.org>, Tim Deegan <tim@xen.org>,
	Xen-devel <xen-devel@lists.xen.org>,
	Stefano Stabellini <stefano.stabellini@citrix.com>,
	Keir Fraser <keir@xen.org>,
	Ian Jackson <ian.jackson@eu.citrix.com>
Subject: Re: [PATCH V15 5/9] xen: Make gpfn related memops compatible with wider return values
Date: Sat, 25 Apr 2015 21:54:39 +0500	[thread overview]
Message-ID: <553BC6CF.4070002@citrix.com> (raw)
In-Reply-To: <5536853F02000078000746EA@mail.emea.novell.com>

Hi Jan,

On 21/04/2015 20:13, Jan Beulich wrote:
> For this specific one - is there a reasonable use case? Other than
> for host PFN, we have control over guest ones, and I'm not sure
> managing a guest with GPFNs extending past 4 billion can be
> expected to work if only this one hypercall got fixed. IOW I'm
> expecting to NAK any such addition without proper rationale.

There is hardware coming out with 48 bits address support (i.e 36 bit pfn).

Even though the current layout of 64bit address space is using 40 bits 
IPA, I wouldn't be surprise if we decide to extend it soon (I have in 
mind PCI passthrough).

Without this new hypercall, you rule out the possibility to run the 
toolstack (included memaccess or any software requiring the maximum PFN 
used by a domain) in a 32bit domain or 32bit userspace on 64bit domain.

I don't have a good use case, but I don't see why we should omit a such 
possibility. It would be better if we can fix now rather than waiting 
until someone need it.

Regards,

-- 
Julien Grall

  parent reply	other threads:[~2015-04-25 16:54 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-20 15:06 [PATCH V15 0/9] Mem_access for ARM Tamas K Lengyel
2015-04-20 15:06 ` [PATCH V15 1/9] xen/arm: groundwork for mem_access support on ARM Tamas K Lengyel
2015-04-20 15:06 ` [PATCH V15 2/9] xen/arm: Allow hypervisor access to mem_access protected pages Tamas K Lengyel
2015-04-21 13:14   ` Ian Campbell
2015-04-21 14:10     ` Tamas K Lengyel
2015-04-21 14:22       ` Ian Campbell
2015-04-20 15:06 ` [PATCH V15 3/9] xen/arm: Data abort exception (R/W) mem_access events Tamas K Lengyel
2015-04-21 13:16   ` Ian Campbell
2015-04-20 15:06 ` [PATCH V15 4/9] xen/arm: Instruction prefetch abort (X) mem_access event handling Tamas K Lengyel
2015-04-21 13:19   ` Ian Campbell
2015-04-20 15:06 ` [PATCH V15 5/9] xen: Make gpfn related memops compatible with wider return values Tamas K Lengyel
2015-04-20 15:22   ` Andrew Cooper
2015-04-20 15:25     ` Tamas K Lengyel
2015-04-21 13:23     ` Ian Campbell
2015-04-21 14:14       ` Jan Beulich
2015-04-21 14:24         ` Ian Campbell
2015-04-21 14:29           ` Jan Beulich
2015-04-21 14:42             ` Tamas K Lengyel
2015-04-21 15:13               ` Jan Beulich
2015-04-21 15:21                 ` Tamas K Lengyel
2015-04-25 16:54                 ` Julien Grall [this message]
2015-04-27  7:02                   ` Jan Beulich
2015-04-27 10:18                     ` Julien Grall
2015-04-21 14:47             ` Ian Campbell
2015-04-21 14:33         ` Tamas K Lengyel
2015-04-21 14:41           ` Jan Beulich
2015-04-20 15:06 ` [PATCH V15 6/9] xen/arm: Implement domain_get_maximum_gpfn Tamas K Lengyel
2015-04-21 13:24   ` Ian Campbell
2015-04-20 15:06 ` [PATCH V15 7/9] tools/libxc: Allocate magic page for mem access on ARM Tamas K Lengyel
2015-04-20 15:06 ` [PATCH V15 8/9] tools/tests: Enable xen-access " Tamas K Lengyel
2015-04-21 13:28   ` Ian Campbell
2015-04-21 14:13     ` Tamas K Lengyel
2015-04-20 15:06 ` [PATCH V15 9/9] xen/arm: Enable mem_access " Tamas K Lengyel
2015-04-22 13:29 ` [PATCH V15 0/9] Mem_access for ARM Ian Campbell

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