linux-kernel - Re: [PATCH] PCI MSI: Yet another fix for MSI-X with NIU cards, v2

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Date:	Thu, 14 May 2009 15:22:42 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Matthew Wilcox <matthew@....cx>
CC:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"David S. Miller" <davem@...emloft.net>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI MSI: Yet another fix for MSI-X with NIU cards, v2

Matthew Wilcox wrote:
> On Wed, May 13, 2009 at 02:06:30PM +0900, Hidetoshi Seto wrote:
>>  		entry->mask_base = base;
>> -		entry->masked = readl(base + j * PCI_MSIX_ENTRY_SIZE +
>> -					PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
>> -		msix_mask_irq(entry, 1);
>> +		entry->masked = 1;
>>  
> 
> Why do you add the setting of entry->masked here?

That was a temporal value for a window between later MSI-X and read/write.
But I agree that using global mask bit like your "Better fix" is better
idea.

>> +	/*
>> +	 * The states of Reserved bits[31:01] of Vector Control for MSI-X
>> +	 * Table Entries must be 0.  However, for potential future use,
>> +	 * software must preserve the value of these reserved bits.
>> +	 * Refer PCI spec 3.0, 6.8.2.9.
>> +	 *
>> +	 * Note that there are some device that refuses access to MSI-X
>> +	 * Table Entries before MSI-X is enabled.  Therefore we do it here. 
>> +	 */
> 
> I think you need to refer to PCIe 2.1 (or an ECN incorporated into it).
> Some of these bits are now used.

Wow, thank you for telling me that PCIe 2.1 is available now!
Anyway I recommend you to add a comment like this, to tell why we do
read/write, and why it is placed here.  It will be help for future
developers not to move this before enable of MSI-X.

>> +	list_for_each_entry(entry, &dev->msi_list, list) {
>> +		int vector = entry->msi_attrib.entry_nr;
>> +		entry->masked = readl(base + vector * PCI_MSIX_ENTRY_SIZE +
>> +					PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
>> +		/* Make sure it is masked */
>> +		msix_mask_irq(entry, 1);
>> +	}
>> +
>>  	return 0;
> 
> This looks to be the same as the replacement patch I sent earlier.

Yes.
I posted it because there were no response from you in last few days.


Thanks,
H.Seto

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