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

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Date:	Mon, 6 Jun 2016 10:28:54 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Jan Beulich <JBeulich@...e.com>
Cc:	David Vrabel <david.vrabel@...rix.com>,
	xen-devel <xen-devel@...ts.xenproject.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Juergen Gross <JGross@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] xen-pciback: return proper values during BAR sizing

On 06/06/2016 09:51 AM, Jan Beulich wrote:
>>>> On 06.06.16 at 15:03, <boris.ostrovsky@...cle.com> wrote:
>> On 06/06/2016 04:11 AM, Jan Beulich wrote:
>>> @@ -225,38 +225,42 @@ static inline void read_dev_bar(struct p
>>>  			   (PCI_BASE_ADDRESS_SPACE_MEMORY |
>>>  				PCI_BASE_ADDRESS_MEM_TYPE_64))) {
>>>  			bar_info->val = res[pos - 1].start >> 32;
>>> -			bar_info->len_val = res[pos - 1].end >> 32;
>>> +			bar_info->len_val = -resource_size(&res[pos - 1]) >> 32;
>>>  			return;
>>>  		}
>>>  	}
>>>  
>>> +	if (!res[pos].flags ||
>>> +	    (res[pos].flags & (IORESOURCE_DISABLED | IORESOURCE_UNSET |
>>> +			       IORESOURCE_BUSY)))
>>> +		return;
>> Why are you not making this check first thing in the routine?
> For one, pos isn't set there yet. And I'd also rather avoid the
> complications resulting from 64-bit memory resources spanning
> two entries.

I thought that both words of a 64-bit BAR would result in a return under
this check so both would be zero. But yes, pos needs to be initialized
anyway (I didn't see this in the diff).

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>