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

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Date:	Wed, 6 Apr 2016 10:00:52 +1000
From:	Gavin Shan <gwshan@...ux.vnet.ibm.com>
To:	Yongji Xie <xyjxie@...ux.vnet.ibm.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, alex.williamson@...hat.com,
	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, eric.auger@...aro.org,
	will.deacon@....com, gwshan@...ux.vnet.ibm.com,
	alistair@...ple.id.au, ruscur@...sell.cc
Subject: Re: [RFC v5 7/7] vfio-pci: Allow to mmap MSI-X table if interrupt
 remapping is supported

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 <xyjxie@...ux.vnet.ibm.com>
>---
> 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.

> 	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


>-- 
>1.7.9.5
>