linux-kernel - Re: [PATCH v2 1/2] xen-pciback: return proper values during BAR sizing

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Date:	Tue, 7 Jun 2016 10:06:44 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Jan Beulich <JBeulich@...e.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Juergen Gross <JGross@...e.com>
Cc:	xen-devel <xen-devel@...ts.xenproject.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] xen-pciback: return proper values during BAR
 sizing

On 06/07/2016 02:30 AM, Jan Beulich wrote:
> Reads following writes with all address bits set to 1 should return all
> changeable address bits as one, not the BAR size (nor, as was the case
> for the upper half of 64-bit BARs, the high half of the region's end
> address). Presumably this didn't cause any problems so far because
> consumers use the value to calculate the size (usually via val & -val),
> and do nothing else with it.
>
> But also consider the exception here: Unimplemented BARs should always
> return all zeroes.
>
> And finally, the check for whether to return the sizing address on read
> for the ROM BAR should ignore all non-address bits, not just the ROM
> Enable one.


Should this go to stable trees as well?

-boris