From: Stefano Stabellini <stefano.stabellini@xilinx.com>
To: Julien Grall <julien@xen.org>
Cc: xen-devel@lists.xenproject.org,
Stefano Stabellini <stefano.stabellini@xilinx.com>,
Volodymyr_Babchuk@epam.com,
Stefano Stabellini <sstabellini@kernel.org>
Subject: Re: [PATCH 10/12] xen/arm: if is_domain_direct_mapped use native UART address for vPL011
Date: Mon, 11 May 2020 15:58:09 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.2005111543330.26167@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <8c01cb1a-0745-3eca-a45d-09c9297163ce@xen.org>
On Sat, 9 May 2020, Julien Grall wrote:
> Hi Stefano,
>
> On 09/05/2020 01:07, Stefano Stabellini wrote:
> > On Fri, 1 May 2020, Julien Grall wrote:
> > > On 01/05/2020 02:26, Stefano Stabellini wrote:
> > > > On Wed, 15 Apr 2020, Julien Grall wrote:
> > > > > Hi Stefano,
> > > > >
> > > > > On 15/04/2020 02:02, Stefano Stabellini wrote:
> > > > > > We always use a fix address to map the vPL011 to domains. The
> > > > > > address
> > > > > > could be a problem for domains that are directly mapped.
> > > > > >
> > > > > > Instead, for domains that are directly mapped, reuse the address of
> > > > > > the
> > > > > > physical UART on the platform to avoid potential clashes.
> > > > >
> > > > > How do you know the physical UART MMIO region is big enough to fit the
> > > > > PL011?
> > > >
> > > > That cannot be because the vPL011 MMIO size is 1 page, which is the
> > > > minimum right?
> > >
> > > No, there are platforms out with multiple UARTs in the same page (see
> > > sunxi
> > > for instance).
> >
> > But if there are multiple UARTs sharing the same page, and the first one
> > is used by Xen, there is no way to assign one of the secondary UARTs to
> > a domU. So there would be no problem choosing the physical UART address
> > for the virtual PL011.
>
> AFAICT, nothing prevents a user to assign such UART to a dom0less guest today.
> It would not be safe, but it should work.
>
> If you want to make it safe, then you would need to trap the MMIO access so
> they can be sanitized. For a UART device, I don't think the overhead would be
> too bad.
>
> Anyway, the only thing I request is to add sanity check in the code to help
> the user diagnostics any potential clash.
OK thanks for clarifying, I'll do that.
next prev parent reply other threads:[~2020-05-11 22:58 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 1:02 [PATCH 0/12] direct-map DomUs Stefano Stabellini
2020-04-15 1:02 ` [PATCH 01/12] xen: introduce xen_dom_flags Stefano Stabellini
2020-04-15 9:12 ` Jan Beulich
2020-04-15 13:26 ` Julien Grall
2020-04-29 23:57 ` Stefano Stabellini
2020-04-15 1:02 ` [PATCH 02/12] xen/arm: introduce arch_xen_dom_flags and direct_map Stefano Stabellini
2020-04-15 10:27 ` Jan Beulich
2020-04-15 11:27 ` Andrew Cooper
2020-04-30 0:34 ` Stefano Stabellini
2020-04-15 1:02 ` [PATCH 03/12] xen/arm: introduce 1:1 mapping for domUs Stefano Stabellini
2020-04-15 13:36 ` Julien Grall
2020-05-01 1:26 ` Stefano Stabellini
2020-05-01 8:30 ` Julien Grall
2020-05-09 0:07 ` Stefano Stabellini
2020-05-09 9:56 ` Julien Grall
2020-04-15 1:02 ` [PATCH 04/12] xen: split alloc_heap_pages in two halves for reusability Stefano Stabellini
2020-04-15 11:22 ` Wei Liu
2020-04-17 10:02 ` Jan Beulich
2020-04-29 23:09 ` Stefano Stabellini
2020-04-15 1:02 ` [PATCH 05/12] xen: introduce reserve_heap_pages Stefano Stabellini
2020-04-15 13:24 ` Julien Grall
2020-04-17 10:11 ` Jan Beulich
2020-04-29 22:46 ` Stefano Stabellini
2020-04-30 6:29 ` Jan Beulich
2020-04-30 16:21 ` Stefano Stabellini
2020-05-04 9:16 ` Jan Beulich
2020-04-30 14:51 ` Julien Grall
2020-04-30 17:00 ` Stefano Stabellini
2020-04-30 18:27 ` Julien Grall
2020-05-12 1:10 ` Stefano Stabellini
2020-05-12 8:57 ` Julien Grall
2020-04-15 1:02 ` [PATCH 06/12] xen/arm: reserve 1:1 memory for direct_map domUs Stefano Stabellini
2020-04-15 13:38 ` Julien Grall
2020-04-15 1:02 ` [PATCH 07/12] xen/arm: new vgic: rename vgic_cpu/dist_base to c/dbase Stefano Stabellini
2020-04-15 13:41 ` Julien Grall
2020-04-15 1:02 ` [PATCH 08/12] xen/arm: if is_domain_direct_mapped use native addresses for GICv2 Stefano Stabellini
2020-04-15 14:00 ` Julien Grall
2020-05-01 1:26 ` Stefano Stabellini
2020-05-01 8:23 ` Julien Grall
2020-05-09 0:06 ` Stefano Stabellini
2020-04-15 1:02 ` [PATCH 09/12] xen/arm: if is_domain_direct_mapped use native addresses for GICv3 Stefano Stabellini
2020-04-15 14:09 ` Julien Grall
2020-05-01 1:31 ` Stefano Stabellini
2020-05-01 8:40 ` Julien Grall
2020-05-09 0:06 ` Stefano Stabellini
2020-04-15 1:02 ` [PATCH 10/12] xen/arm: if is_domain_direct_mapped use native UART address for vPL011 Stefano Stabellini
2020-04-15 14:11 ` Julien Grall
2020-05-01 1:26 ` Stefano Stabellini
2020-05-01 8:09 ` Julien Grall
2020-05-09 0:07 ` Stefano Stabellini
2020-05-09 10:11 ` Julien Grall
2020-05-11 22:58 ` Stefano Stabellini [this message]
2020-04-15 1:02 ` [PATCH 11/12] xen/arm: if xen_force don't try to setup the IOMMU Stefano Stabellini
2020-04-15 14:12 ` Julien Grall
2020-04-29 21:55 ` Stefano Stabellini
2020-04-30 13:51 ` Julien Grall
2020-05-01 1:25 ` Stefano Stabellini
2020-04-15 1:02 ` [PATCH 12/12] xen/arm: call iomem_permit_access for passthrough devices Stefano Stabellini
2020-04-15 14:18 ` Julien Grall
2020-04-29 20:47 ` Stefano Stabellini
2020-04-30 13:01 ` Julien Grall
2020-05-24 14:12 ` Julien Grall
2020-05-26 16:46 ` Stefano Stabellini
2020-05-27 18:09 ` Julien Grall
2020-04-16 8:59 ` [PATCH 0/12] direct-map DomUs Julien Grall
2020-04-29 20:16 ` Stefano Stabellini
2020-04-30 12:54 ` Julien Grall
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