linux-kernel - Re: [PATCH 5/9] apm32: remove paravirt

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Message-ID: <56C72FFB.5090105@oracle.com>
Date:	Fri, 19 Feb 2016 10:08:43 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>, bp@...en8.de
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, luto@...capital.net,
	rusty@...tcorp.com.au, david.vrabel@...rix.com,
	konrad.wilk@...cle.com, xen-devel@...ts.xensource.com
Subject: Re: [PATCH 5/9] apm32: remove paravirt_enabled() use



On 02/19/2016 08:08 AM, Luis R. Rodriguez wrote:
> There is already a check for apm_info.bios == 0, the
> apm_info.bios is set from the boot_params.apm_bios_info.
> Both Xen and lguest, which are also the only ones that set
> paravirt_enabled to true) do never set the apm_bios_info,
> the paravirt_enabled() check is simply not needed.

We need to guarantee that boot_params is filled with zeroes. On 
baremetal path we clear .bss (which is where boot_params live) before 
copying data from zero page.

So we need to at least memset(&boot_params, 0, sz) in 
xen_start_kernel(). Better yet, clear whole .bss.

(This applies to the next patch as well).

-boris