linux-kernel - Re: [RFC PATCH v3 5/5] vfio-pci: Allow to mmap MSI-X table if host bridge supports filtering of MSIs

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Date:	Fri, 29 Jan 2016 18:42:35 +0800
From:	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
To:	Alex Williamson <alex.williamson@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-doc@...r.kernel.org
Cc:	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 v3 5/5] vfio-pci: Allow to mmap MSI-X table if host
 bridge supports filtering of MSIs

On 2016/1/29 6:46, Alex Williamson wrote:
> On Fri, 2016-01-15 at 15:06 +0800, Yongji Xie wrote:
>> Current vfio-pci implementation disallows to mmap MSI-X
>> table in case that user get to touch this directly.
>>   
>> But we should allow to mmap these MSI-X tables if the PCI
>> host bridge supports filtering of MSIs.
>>   
>> Signed-off-by: Yongji Xie <xyjxie@...ux.vnet.ibm.com>
>> ---
>>   drivers/vfio/pci/vfio_pci.c |    6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>   
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index 11fd0f0..4d68f6a 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -555,7 +555,8 @@ static long vfio_pci_ioctl(void *device_data,
>>   			    IORESOURCE_MEM && !pci_resources_share_page(pdev,
>>   			    info.index)) {
>>   				info.flags |= VFIO_REGION_INFO_FLAG_MMAP;
>> -				if (info.index == vdev->msix_bar) {
>> +				if (!pci_host_bridge_msi_filtered_enabled(pdev) &&
>> +				    info.index == vdev->msix_bar) {
>>   					ret = msix_sparse_mmap_cap(vdev, &caps);
>>   					if (ret)
>>   						return ret;
>> @@ -967,7 +968,8 @@ static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
>>   	if (phys_len < PAGE_SIZE || req_start + req_len > phys_len)
>>   		return -EINVAL;
>>   
>> -	if (index == vdev->msix_bar) {
>> +	if (!pci_host_bridge_msi_filtered_enabled(pdev) &&
>> +	    index == vdev->msix_bar) {
>>   		/*
>>   		 * Disallow mmaps overlapping the MSI-X table; users don't
>>   		 * get to touch this directly.  We could find somewhere
> What about read()/write() access, why would we allow mmap() but not
> those?
>

Yes, you are right! I miss the MSI-X table check in vfio_pci_bar_rw().
I will fix it in next version. Thanks.

Regards,
Yongji Xie