From: Andrii Anisov <andrii.anisov@gmail.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Julien Grall <julien.grall@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>,
"LOPEZ, FUENTES NACARINO Jairo Eduardo" <jairo@ruri.waseda.jp>,
xen-devel@lists.xen.org
Subject: Re: RT Xen on ARM - R-Car series
Date: Tue, 12 Feb 2019 20:21:32 +0200 [thread overview]
Message-ID: <316d93d5-7b4d-ace3-9bfa-7680057e92bd@gmail.com> (raw)
In-Reply-To: <20190207103513.ky7xnftn3pj7r2lf@mac>
Hello Roger,
Sorry for a delayed response.
On 07.02.19 12:35, Roger Pau Monné wrote:
> I've been thinking about this with other Citrix folks, and I'm not
> sure the proposed patch is a good solution. It's not possible for us
> to know whether there's a kernel somewhere relying on changing the
> virtual address of the runtime state area without issuing a new
> hypercall.
Do you mean allocating another buffer by VM and mapping it to a virtual address known to XEN? Or remapping existing buffer to a different virtual address?
> If such kernel existed by making this change we would introduce random
> memory corruption to that kernel, which would be very hard to track
> and considered a regression.
I guess you actually mean that VM is trying to map another physical buffer to a vaddr known to XEN. As I said here [1], even current implementation looks problematic, because VM's changes in PT are not atomic from the hypervisor point of view.
I stated that for ARM, but x86 does not seem to differ here.
Actually VM trying to make changes behind a hypervisor's back is a really bad idea. Because the hypervisor *is* always behind the VM's back.
> I think the best way to move forward is to pick my patch and introduce
> a new hypercall that instead of a virtual address takes a guest
> physical address. Will you be OK with this Andrii?
It might work better for this. And introducing a new interface is a chance to get rid of a mixed legacy.
> Note that the Linux kernel would also need to be modified to make use
> of this new hypercall, but that's likely close to a 1 line change.I would not say it is a 1 line change.
I think about a page alignment for the runstate area, I'd like to have it directly accessed from XEN. I do not like `update_runstate_area()` with its all kind of copy_to_guest, done twice a context switch.
[1] https://lists.xenproject.org/archives/html/xen-devel/2019-02/msg00164.html
--
Sincerely,
Andrii Anisov.
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next prev parent reply other threads:[~2019-02-12 18:21 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CACrvCsaeHuwzZzUQTzNYF7fqmgQWNJUVOQZv9D0MnYrXjqzZtQ@mail.gmail.com>
2018-12-22 12:21 ` RT Xen on ARM - R-Car series Andrii Anisov
2018-12-25 16:07 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2018-12-27 11:07 ` Andrii Anisov
2018-12-28 15:22 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2018-12-28 8:28 ` Andrii Anisov
2018-12-28 8:32 ` Andrii Anisov
2018-12-28 8:39 ` Andrii Anisov
2019-01-04 9:09 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2019-01-08 17:04 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2019-01-11 20:12 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2019-01-14 8:42 ` Andrii Anisov
2019-01-16 7:53 ` Andrii Anisov
2019-01-21 18:04 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
[not found] ` <CACrvCsZB-tps6=Vr=1Phf5oo5eUReabMLJzkbO3d2hmNLDOxww@mail.gmail.com>
[not found] ` <7e217489-2c1a-c35f-d51f-0969654aa8cc@gmail.com>
[not found] ` <CACrvCsaYJ-zGkZwfdV7BXDABW8u_EDQetU3pq+2otRGXWTXagw@mail.gmail.com>
[not found] ` <4d078801-b804-06e7-ad5c-8032b1dbaa84@gmail.com>
2019-01-28 17:20 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2019-01-28 8:25 ` Andrii Anisov
2019-01-29 15:30 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2019-01-29 13:29 ` Andrii Anisov
2019-01-30 20:23 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2019-01-30 12:12 ` Julien Grall
2019-01-31 11:22 ` Andrii Anisov
2019-01-31 11:37 ` Julien Grall
2019-01-31 12:00 ` Andrii Anisov
2019-01-31 12:20 ` Julien Grall
2019-01-31 21:56 ` Stefano Stabellini
2019-01-31 23:14 ` Julien Grall
2019-02-01 10:02 ` Andrii Anisov
2019-02-01 10:12 ` Julien Grall
2019-02-01 10:35 ` Andrii Anisov
2019-02-01 11:06 ` Julien Grall
2019-02-01 16:53 ` Roger Pau Monné
2019-02-01 17:40 ` Julien Grall
2019-02-04 10:28 ` Andrii Anisov
2019-02-04 11:21 ` Julien Grall
2019-02-04 14:46 ` Andrii Anisov
2019-02-04 15:05 ` Julien Grall
2019-02-04 12:53 ` Roger Pau Monné
2019-02-04 21:58 ` Julien Grall
2019-02-05 8:40 ` Andrii Anisov
2019-02-05 9:45 ` Roger Pau Monné
2019-02-05 9:54 ` Andrii Anisov
2019-02-05 10:10 ` Roger Pau Monné
2019-02-06 20:20 ` Andrii Anisov
2019-02-06 21:03 ` Stefano Stabellini
2019-02-07 9:42 ` Andrii Anisov
2019-02-07 10:35 ` Roger Pau Monné
2019-02-07 10:59 ` Julien Grall
2019-02-12 18:21 ` Andrii Anisov
2019-02-12 19:21 ` Julien Grall
2019-02-14 14:18 ` Andrii Anisov
2019-02-14 17:29 ` Julien Grall
2019-02-15 11:30 ` Andrii Anisov
2019-02-15 17:13 ` Julien Grall
2019-02-15 17:41 ` Andrii Anisov
2019-02-16 8:42 ` Julien Grall
2019-02-12 18:21 ` Andrii Anisov [this message]
2019-02-14 16:29 ` Roger Pau Monné
2019-02-15 15:21 ` Andrii Anisov
2019-02-15 16:31 ` Julien Grall
2019-02-15 17:30 ` Andrii Anisov
2019-02-15 18:36 ` Julien Grall
2019-02-14 17:08 ` Julien Grall
2019-02-05 9:26 ` Roger Pau Monné
2019-02-01 10:07 ` Andrii Anisov
2019-02-01 10:16 ` Julien Grall
2019-02-01 10:35 ` Andrii Anisov
2019-02-01 10:51 ` Julien Grall
2019-02-01 18:00 ` Stefano Stabellini
2019-02-04 10:32 ` Andrii Anisov
2019-02-04 11:36 ` Julien Grall
2019-02-04 15:19 ` Andrii Anisov
2019-02-04 22:06 ` Julien Grall
2019-02-05 9:01 ` Andrii Anisov
2019-02-05 19:18 ` Stefano Stabellini
2019-02-07 10:53 ` Andrii Anisov
[not found] ` <CACrvCsbkFG=3To83qi7xxmtmgC_9PKvuLz73edhiaV7TsJAZqQ@mail.gmail.com>
2019-01-31 12:24 ` Julien Grall
2019-01-16 20:46 ` Andrii Anisov
2019-01-16 7:40 ` Andrii Anisov
2019-01-17 2:08 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
2018-12-28 17:35 ` LOPEZ, FUENTES NACARINO Jairo Eduardo
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