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Re: [Qemu-devel] vexpress: Framebuffer broken with KVM enabled


From: Anup Patel
Subject: Re: [Qemu-devel] vexpress: Framebuffer broken with KVM enabled
Date: Mon, 16 Feb 2015 14:50:02 +0530

On Mon, Feb 16, 2015 at 2:43 PM, Jan Kiszka <address@hidden> wrote:
> Hi,
>
> next issue related to KVM/QEMU on the TK1: The guest image I'm running
> gives proper framebuffer output when in emulation mode. Once KVM is
> enabled, the screen is - at best - only initially updated. Sometimes I
> see the famous tux images and a bit of the console texts, but usually it
> stays black. Explanations?

The QEMU accesses Guest Video RAM (or any portion of Guest RAM) as
cacheable user space memory. The Guest Kernel might access Guest Video
RAM as non-cacheable to maintain coherency with video device. If this is
the case then all updates by Guest kernel to Guest Video RAM will not
be visible to QEMU.

--
Anup

>
> Jan
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