linux-kernel - Re: [RFC PATCH v4 5/7] vfio-pci: Allow to mmap sub-page MMIO BARs if the mmio page is exclusive

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Message-ID: <56EA9532.2050902@linux.vnet.ibm.com>
Date:	Thu, 17 Mar 2016 19:29:54 +0800
From:	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-doc@...r.kernel.org, bhelgaas@...gle.com, corbet@....net,
	aik@...abs.ru, benh@...nel.crashing.org, paulus@...ba.org,
	mpe@...erman.id.au, warrier@...ux.vnet.ibm.com,
	zhong@...ux.vnet.ibm.com, nikunj@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH v4 5/7] vfio-pci: Allow to mmap sub-page MMIO BARs if
 the mmio page is exclusive

On 2016/3/17 0:30, Alex Williamson wrote:
> On Mon,  7 Mar 2016 15:48:36 +0800
> Yongji Xie <xyjxie@...ux.vnet.ibm.com> wrote:
>
>> Current vfio-pci implementation disallows to mmap
>> sub-page(size < PAGE_SIZE) MMIO BARs because these BARs' mmio
>> page may be shared with other BARs.
>>
>> But we should allow to mmap these sub-page MMIO BARs if PCI
>> resource allocator can make sure these BARs' mmio page will
>> not be shared with other BARs.
>>
>> Signed-off-by: Yongji Xie <xyjxie@...ux.vnet.ibm.com>
>> ---
>>   drivers/vfio/pci/vfio_pci.c |    7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index 1ce1d36..49d7a69 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -589,7 +589,8 @@ static long vfio_pci_ioctl(void *device_data,
>>   				     VFIO_REGION_INFO_FLAG_WRITE;
>>   			if (IS_ENABLED(CONFIG_VFIO_PCI_MMAP) &&
>>   			    pci_resource_flags(pdev, info.index) &
>> -			    IORESOURCE_MEM && info.size >= PAGE_SIZE) {
>> +			    IORESOURCE_MEM && !pci_resources_share_page(pdev,
>> +			    info.index)) {
> this would be a preferable line wrap:
>
>                              IORESOURCE_MEM &&
>                              !pci_resources_share_page(pdev, info.index)) {

OK. I'll fix it.

Thanks,
Yongji Xie