linux-kernel - Re: [PATCH 2/3] Refactor msi/msix restore code Part2

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Message-ID: <51F0CB10.1070500@oracle.com>
Date:	Thu, 25 Jul 2013 14:52:00 +0800
From:	Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	linux-pci@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	xen-devel <xen-devel@...ts.xen.org>, bhelgaas@...gle.com,
	Feng Jin <joe.jin@...cle.com>,
	Sucheta Chakraborty <sucheta.chakraborty@...gic.com>
Subject: Re: [PATCH 2/3] Refactor msi/msix restore code Part2


On 2013-07-24 21:46, Konrad Rzeszutek Wilk wrote:
> On Wed, Jul 24, 2013 at 11:08:10AM +0800, Zhenzhong Duan wrote:
>> xen_initdom_restore_msi_irqs trigger a hypercall to restore addr/data/mask
>> in dom0. It's better to do the same for default_restore_msi_irqs in baremetal.
>>
>> Move restore of mask in default_restore_msi_irqs, this could avoid mask
>> restored twice in dom0, once in hypercall, the other in kernel.
> Why not remove the hypercall then?
If removed, msi entry couldn't be restored, such as pci_reset_function 
who will reset pci registers.
> Or alter the function to detect
> whether the restore of the mask has occurred?
Then we need to add the check for dom0 only.
>
>> Without that, qlcnic driver calling pci_reset_function will lost interrupt
>> in dom0.
>>
>> Tested-by: Sucheta Chakraborty <sucheta.chakraborty@...gic.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
>> ---
>>   drivers/pci/msi.c |   17 ++++++++++++++---
>>   1 files changed, 14 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
>> index 87223ae..922fb49 100644
>> --- a/drivers/pci/msi.c
>> +++ b/drivers/pci/msi.c
>> @@ -216,6 +216,8 @@ void unmask_msi_irq(struct irq_data *data)
>>   #ifdef HAVE_DEFAULT_MSI_RESTORE_IRQS
>>   void default_restore_msi_irqs(struct pci_dev *dev, int irq)
>>   {
>> +	int pos;
>> +	u16 control;
>>   	struct msi_desc *entry;
>>   
>>   	entry = NULL;
>> @@ -228,8 +230,19 @@ void default_restore_msi_irqs(struct pci_dev *dev, int irq)
>>   		entry = irq_get_msi_desc(irq);
>>   	}
>>   
>> -	if (entry)
>> +	if (entry) {
>>   		write_msi_msg(irq, &entry->msg);
>> +		if (dev->msix_enabled) {
>> +			msix_mask_irq(entry, entry->masked);
>> +			readl(entry->mask_base);
>> +		} else {
>> +			pos = entry->msi_attrib.pos;
>> +			pci_read_config_word(dev, pos + PCI_MSI_FLAGS,
>> +					     &control);
>> +			msi_mask_irq(entry, msi_capable_mask(control),
>> +				     entry->masked);
>> +		}
>> +	}
>>   }
>>   #endif
>>   
>> @@ -406,7 +419,6 @@ static void __pci_restore_msi_state(struct pci_dev *dev)
>>   	arch_restore_msi_irqs(dev, dev->irq);
>>   
>>   	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
>> -	msi_mask_irq(entry, msi_capable_mask(control), entry->masked);
> Before this patch we had:
>
> 	write_msi_msg(..)
> 	pci_read_config_work(PCI_MSI_FLAGS, &control)
> 	pci_write_config_dword(~msi_capable_mask(control) | entry->masked)
> 	control &= ~_PCI_MSI_FLAGS_QSIZE;
> 	control |= ...
> 	pci_write_config_dword(PCI_MSI_FLAGS, control)
>
> while with this you have now:
>
> 	write_msi_msg(..)
> 	pci_read_config_work(PCI_MSI_FLAGS, &_control)
> 	pci_write_config_dword(~msi_capable_mask(_control) | entry->masked)
> --> 	pci_read_config_work(PCI_MSI_FLAGS, &control)
> 	control &= ~_PCI_MSI_FLAGS_QSIZE;
> 	control |= ...
> 	pci_write_config_dword(PCI_MSI_FLAGS, control)
>
> see the problem? The 'control' value in __pci_restore_msi_state reads the
> value _after_ it has been masked (which is now done in default_restore_msi_irqs).
>
> Wouldn't that cause problems?
>
pci_write_config_dword(~msi_capable_mask(_control) | entry->masked) restore per vector
msi mask bits based on the support of PCI_MSI_FLAGS_MASKBIT. This is different from the
global mask bit in PCI_MSI_FLAGS.

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