Subject: Re: [RFC v5 7/7] vfio-pci: Allow to mmap MSI-X table if interrupt remapping is supported

From: Yongji Xie <[email-masked]>
Date: Wed, 6 Apr 2016 11:28:48 +0800

On 2016/4/6 8:00, Gavin Shan wrote:
> On Tue, Apr 05, 2016 at 09:46:44PM +0800, Yongji Xie wrote:
>> This patch enables mmapping MSI-X tables if
>> hardware supports interrupt remapping which
>> can ensure that a given pci device can only
>> shoot the MSIs assigned for it.
>>
>> Signed-off-by: Yongji Xie <[email-masked]>
>> ---
>> drivers/vfio/pci/vfio_pci.c         |    9 +++++++--
>> drivers/vfio/pci/vfio_pci_private.h |    1 +
>> drivers/vfio/pci/vfio_pci_rdwr.c    |    2 +-
>> 3 files changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index c60d790..ef02896 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -201,6 +201,10 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
>> 	} else
>> 		vdev->msix_bar = 0xFF;
>>
>> +	if (iommu_capable(pdev->dev.bus, IOMMU_CAP_INTR_REMAP) ||
>> +		pdev->bus->bus_flags | PCI_BUS_FLAGS_MSI_REMAP)
>> +		vdev->msi_remap = true;
>> +
> I guess you probably need a "&" here. Otherwise, the condition
> is always true.

Yes, you are right. I'll fix it.

>> 	if (!vfio_vga_disabled() && vfio_pci_is_vga(pdev))
>> 		vdev->has_vga = true;
>>
>> @@ -635,7 +639,8 @@ static long vfio_pci_ioctl(void *device_data,
>> 				     VFIO_REGION_INFO_FLAG_WRITE;
>> 			if (vdev->bar_mmap_supported[info.index]) {
>> 				info.flags |= VFIO_REGION_INFO_FLAG_MMAP;
>> -				if (info.index == vdev->msix_bar) {
>> +				if (info.index == vdev->msix_bar &&
>> +						!vdev->msi_remap) {
>> 					ret = msix_sparse_mmap_cap(vdev, &caps);
>> 					if (ret)
>> 						return ret;
>> @@ -1067,7 +1072,7 @@ static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
>> 	if (req_start + req_len > phys_len)
>> 		return -EINVAL;
>>
>> -	if (index == vdev->msix_bar) {
>> +	if (index == vdev->msix_bar && !vdev->msi_remap) {
>> 		/*
>> 		 * Disallow mmaps overlapping the MSI-X table; users don't
>> 		 * get to touch this directly.  We could find somewhere
>> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
>> index 0ea4c62..4f20963 100644
>> --- a/drivers/vfio/pci/vfio_pci_private.h
>> +++ b/drivers/vfio/pci/vfio_pci_private.h
>> @@ -78,6 +78,7 @@ struct vfio_pci_device {
>> 	int			irq_type;
>> 	int			num_regions;
>> 	struct vfio_pci_region	*region;
>> +	bool			msi_remap;
>> 	u8			msi_qmax;
>> 	u8			msix_bar;
>> 	u16			msix_size;
>> diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
>> index 5ffd1d9..606ee3c 100644
>> --- a/drivers/vfio/pci/vfio_pci_rdwr.c
>> +++ b/drivers/vfio/pci/vfio_pci_rdwr.c
>> @@ -164,7 +164,7 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
>> 	} else
>> 		io = vdev->barmap[bar];
>>
>> -	if (bar == vdev->msix_bar) {
>> +	if (bar == vdev->msix_bar && !vdev->msi_remap) {
>> 		x_start = vdev->msix_offset;
>> 		x_end = vdev->msix_offset + vdev->msix_size;
>> 	}
> When PCI_BUS_FLAGS_MSI_REMAP is set, the MSIx table can be accessed by
> read/write interface except mmap(). The commit log doesn't mention it.
> It would be better if you have some words about it.
>
> Thanks,
> Gavin
>

OK. I will mention it in commit log.

Thanks,
Yongji

>> -- 
>> 1.7.9.5