On Mon, Sep 03, 2018 at 10:55:57AM +0800, Lu Baolu wrote:

Date: Mon, 3 Sep 2018 10:55:57 +0800
From: Lu Baolu <baolu.lu@linux.intel.com>
To: Kenneth Lee <redacted>, Jonathan Corbet <corbet@lwn.net>,
 Herbert Xu [off-list ref], "David S . Miller"
 [off-list ref], Joerg Roedel [off-list ref], Alex Williamson
 [off-list ref], Kenneth Lee [off-list ref], Hao
 Fang [off-list ref], Zhou Wang [off-list ref], Zaibo Xu
 [off-list ref], Philippe Ombredanne [off-list ref], Greg
 Kroah-Hartman [off-list ref], Thomas Gleixner
 [off-list ref], linux-doc@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
 iommu@lists.linux-foundation.org, kvm@vger.kernel.org,
 linux-accelerators@lists.ozlabs.org, Sanjay Kumar
 [off-list ref]
CC: linuxarm@huawei.com, baolu.lu@linux.intel.com
Subject: Re: [PATCH 3/7] vfio: add sdmdev support
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Message-ID: [ref]

Hi,

On 09/03/2018 08:52 AM, Kenneth Lee wrote:

quoted

From: Kenneth Lee <redacted>

SDMDEV is "Share Domain Mdev". It is a vfio-mdev. But differ from
the general vfio-mdev, it shares its parent's IOMMU. If Multi-PASID
support is enabled in the IOMMU (not yet in the current kernel HEAD),
multiple process can share the IOMMU by different PASID. If it is not
support, only one process can share the IOMMU with the kernel driver.

If only for share domain purpose, I don't think it's necessary to create
a new device type.

Yes, if ONLY for share domain purpose. But we need also to share the interrupt.

quoted

Currently only the vfio type-1 driver is updated to make it to be aware
of.

Signed-off-by: Kenneth Lee <redacted>
Signed-off-by: Zaibo Xu <redacted>
Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
---
 drivers/vfio/Kconfig              |   1 +
 drivers/vfio/Makefile             |   1 +
 drivers/vfio/sdmdev/Kconfig       |  10 +
 drivers/vfio/sdmdev/Makefile      |   3 +
 drivers/vfio/sdmdev/vfio_sdmdev.c | 363 ++++++++++++++++++++++++++++++
 drivers/vfio/vfio_iommu_type1.c   | 151 ++++++++++++-
 include/linux/vfio_sdmdev.h       |  96 ++++++++
 include/uapi/linux/vfio_sdmdev.h  |  29 +++
 8 files changed, 648 insertions(+), 6 deletions(-)
 create mode 100644 drivers/vfio/sdmdev/Kconfig
 create mode 100644 drivers/vfio/sdmdev/Makefile
 create mode 100644 drivers/vfio/sdmdev/vfio_sdmdev.c
 create mode 100644 include/linux/vfio_sdmdev.h
 create mode 100644 include/uapi/linux/vfio_sdmdev.h

[--cut for short --]

quoted

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index d9fd3188615d..ba73231d8692 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c

@@ -41,6 +41,7 @@
 #include <linux/notifier.h>
 #include <linux/dma-iommu.h>
 #include <linux/irqdomain.h>
+#include <linux/vfio_sdmdev.h>
 #define DRIVER_VERSION  "0.2"
 #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@redhat.com>"

@@ -89,6 +90,8 @@ struct vfio_dma {
 };
 struct vfio_group {
+	/* iommu_group of mdev's parent device */
+	struct iommu_group	*parent_group;
 	struct iommu_group	*iommu_group;
 	struct list_head	next;
 };

@@ -1327,6 +1330,109 @@ static bool vfio_iommu_has_sw_msi(struct iommu_group *group, phys_addr_t *base)
 	return ret;
 }
+/* return 0 if the device is not sdmdev.
+ * return 1 if the device is sdmdev, the data will be updated with parent
+ *	device's group.
+ * return -errno if other error.
+ */
+static int vfio_sdmdev_type(struct device *dev, void *data)
+{
+	struct iommu_group **group = data;
+	struct iommu_group *pgroup;
+	int (*_is_sdmdev)(struct device *dev);
+	struct device *pdev;
+	int ret = 1;
+
+	/* vfio_sdmdev module is not configurated */
+	_is_sdmdev = symbol_get(vfio_sdmdev_is_sdmdev);
+	if (!_is_sdmdev)
+		return 0;
+
+	/* check if it belongs to vfio_sdmdev device */
+	if (!_is_sdmdev(dev)) {
+		ret = 0;
+		goto out;
+	}
+
+	pdev = dev->parent;
+	pgroup = iommu_group_get(pdev);
+	if (!pgroup) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (group) {
+		/* check if all parent devices is the same */
+		if (*group && *group != pgroup)
+			ret = -ENODEV;
+		else
+			*group = pgroup;
+	}
+
+	iommu_group_put(pgroup);
+
+out:
+	symbol_put(vfio_sdmdev_is_sdmdev);
+
+	return ret;
+}
+
+/* return 0 or -errno */
+static int vfio_sdmdev_bus(struct device *dev, void *data)
+{
+	struct bus_type **bus = data;
+
+	if (!dev->bus)
+		return -ENODEV;
+
+	/* ensure all devices has the same bus_type */
+	if (*bus && *bus != dev->bus)
+		return -EINVAL;
+
+	*bus = dev->bus;
+	return 0;
+}
+
+/* return 0 means it is not sd group, 1 means it is, or -EXXX for error */
+static int vfio_iommu_type1_attach_sdgroup(struct vfio_domain *domain,
+					    struct vfio_group *group,
+					    struct iommu_group *iommu_group)
+{
+	int ret;
+	struct bus_type *pbus = NULL;
+	struct iommu_group *pgroup = NULL;
+
+	ret = iommu_group_for_each_dev(iommu_group, &pgroup,
+				       vfio_sdmdev_type);
+	if (ret < 0)
+		goto out;
+	else if (ret > 0) {
+		domain->domain = iommu_group_share_domain(pgroup);
+		if (IS_ERR(domain->domain))
+			goto out;
+		ret = iommu_group_for_each_dev(pgroup, &pbus,
+				       vfio_sdmdev_bus);
+		if (ret < 0)
+			goto err_with_share_domain;
+
+		if (pbus && iommu_capable(pbus, IOMMU_CAP_CACHE_COHERENCY))
+			domain->prot |= IOMMU_CACHE;
+
+		group->parent_group = pgroup;
+		INIT_LIST_HEAD(&domain->group_list);
+		list_add(&group->next, &domain->group_list);
+
+		return 1;
+	}

This doesn't match the function name. It only gets the domain from the
parent device. It hasn't been really attached.

quoted

+
+	return 0;
+
+err_with_share_domain:
+	iommu_group_unshare_domain(pgroup);
+out:
+	return ret;
+}
+
 static int vfio_iommu_type1_attach_group(void *iommu_data,
 					 struct iommu_group *iommu_group)
 {

@@ -1335,8 +1441,8 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 	struct vfio_domain *domain, *d;
 	struct bus_type *bus = NULL, *mdev_bus;
 	int ret;
-	bool resv_msi, msi_remap;
-	phys_addr_t resv_msi_base;
+	bool resv_msi = false, msi_remap;
+	phys_addr_t resv_msi_base = 0;
 	mutex_lock(&iommu->lock);

@@ -1373,6 +1479,14 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 	if (mdev_bus) {
 		if ((bus == mdev_bus) && !iommu_present(bus)) {
 			symbol_put(mdev_bus_type);
+
+			ret = vfio_iommu_type1_attach_sdgroup(domain, group,
+					iommu_group);
+			if (ret < 0)
+				goto out_free;
+			else if (ret > 0)
+				goto replay_check;

Here you get the domain from the parent device and save it for later
use. The actual attaching is ignored.

I don't think this follows the philosophy of this function. It actually
make all devices in the group with the same bus type to share a single
domain.

I think the original logic here is:

1. Create a new vfio_domain along with a iommu_domain for the group attached to
   the container
2. Try to match the vfio_domain with the domain list in the container. If there
   is a match, free the created one and and reuse it, or add the new vfio_domain
   to the list. 

   With this design, the same configuration to the IOMMU(unit) will be applied
   only once.


For iommu_group that shares IOMMU with its parent, the configuration will never
be the same (The PASID will be different), so it is not necessary to merge them.

Further more, the parent domain might be a domain of type
IOMMU_DOMAIN_DMA. That will not be able to use as an
IOMMU_DOMAIN_UNMANAGED domain for iommu APIs.

Indeed, it should be checked when the domain is shared. Unmanaged domain should
not be used for sharing. I will update it in the future.

Best regards,
Lu Baolu

-- 
			-Kenneth(Hisilicon)

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