linux-kernel - Re: [RFC] arm64: Early printk support for virtio-mmio console devices.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130419093953.GD13283@mudshark.cambridge.arm.com>
Date:	Fri, 19 Apr 2013 10:39:53 +0100
From:	Will Deacon <will.deacon@....com>
To:	Pranavkumar Sawargaonkar <pranavkumar@...aro.org>
Cc:	Peter Maydell <peter.maydell@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Patch Tracking <patches@...aro.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC] arm64: Early printk support for virtio-mmio console
 devices.

On Fri, Apr 19, 2013 at 10:34:56AM +0100, Pranavkumar Sawargaonkar wrote:
> On 19 April 2013 15:00, Peter Maydell <peter.maydell@...aro.org> wrote:
> > On 19 April 2013 10:27, Will Deacon <will.deacon@....com> wrote:
> >> On Fri, Apr 19, 2013 at 10:25:35AM +0100, Pranavkumar Sawargaonkar wrote:
> >>> I am not against using 8250 emulation (as far as it solves printk
> >>> issues for kernel booting logs), but my point is why not to add early
> >>> read-write support for virtio console, which also can be useful in
> >>> emulation less mach-virt environment also ?
> >>
> >> We can have both, but only one of those requires a change to the virtio
> >> specification.
> >
> > I don't think avoiding writing a spec is necessarily a good reason
> > for insisting on emulation of a lump of hardware 95% of whose
> > capabilities you aren't going to use...
> 
> True.
> Also 8250 will require emulation of registers, and i am not sure about
> if mach-virt will have any emulation of real hw ?

The point of mach-virt is that it is completely parameterised. So, if you're
not emulating an 8250, then don't tell the kernel that you have one!
Similarly, if you *do* emulate it, then either create a device-tree node for
it or pass the appropriate earlyprintk= string on the command line.

As far as kvmtool is concerned, we'd probably have a new command-line option
for arm64, allowing you to specify the early console device.

Will
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/