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Message-ID: <85e5cb11-ab58-5433-d456-fa831f4deccf@gmail.com>
Date: Fri, 21 Oct 2022 09:08:37 +0300
From: Xenia Ragiadakou <burzalodowa@...il.com>
To: Oleksandr Tyshchenko <Oleksandr_Tyshchenko@...m.com>
Cc: "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Juergen Gross <jgross@...e.com>,
Stefano Stabellini <sstabellini@...nel.org>,
Oleksandr Tyshchenko <olekstysh@...il.com>
Subject: Re: [PATCH V2] xen/virtio: Handle PCI devices which Host controller
is described in DT
On 10/20/22 23:07, Oleksandr Tyshchenko wrote:
Hi Oleksandr
>
> On 20.10.22 21:11, Xenia Ragiadakou wrote:
>
> Hello Xenia
>
>
>> On 10/20/22 17:12, Oleksandr Tyshchenko wrote:
>>>
>>> On 20.10.22 11:24, Xenia Ragiadakou wrote:
>>>> On 10/19/22 22:41, Oleksandr Tyshchenko wrote:
>>>>
>>>> Hi Oleksandr
>>>
>>>
>>> Hello Xenia
>>>
>>>
>>>>
>>>>>
>>>>> On 19.10.22 11:47, Xenia Ragiadakou wrote:
>>>>>
>>>>> Hello Xenia
>>>>>
>>>>>> On 10/19/22 03:58, Stefano Stabellini wrote:
>>>>>>> On Sat, 15 Oct 2022, Oleksandr Tyshchenko wrote:
>>>>>>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
>>>>>>>>
>>>>>>>> Use the same "xen-grant-dma" device concept for the PCI devices
>>>>>>>> behind device-tree based PCI Host controller, but with one
>>>>>>>> modification.
>>>>>>>> Unlike for platform devices, we cannot use generic IOMMU bindings
>>>>>>>> (iommus property), as we need to support more flexible
>>>>>>>> configuration.
>>>>>>>> The problem is that PCI devices under the single PCI Host
>>>>>>>> controller
>>>>>>>> may have the backends running in different Xen domains and thus
>>>>>>>> have
>>>>>>>> different endpoints ID (backend domains ID).
>>>>>>>>
>>>>>>>> So use generic PCI-IOMMU bindings instead (iommu-map/iommu-map-mask
>>>>>>>> properties) which allows us to describe relationship between PCI
>>>>>>>> devices and backend domains ID properly.
>>>>>>>>
>>>>>>>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
>>>>>>>
>>>>>>> Now that I understood the approach and the reasons for it, I can
>>>>>>> review
>>>>>>> the patch :-)
>>>>>>>
>>>>>>> Please add an example of the bindings in the commit message.
>>>>>>>
>>>>>>>
>>>>>>>> ---
>>>>>>>> Slightly RFC. This is needed to support Xen grant mappings for
>>>>>>>> virtio-pci devices
>>>>>>>> on Arm at some point in the future. The Xen toolstack side is not
>>>>>>>> completely ready yet.
>>>>>>>> Here, for PCI devices we use more flexible way to pass backend
>>>>>>>> domid
>>>>>>>> to the guest
>>>>>>>> than for platform devices.
>>>>>>>>
>>>>>>>> Changes V1 -> V2:
>>>>>>>> - update commit description
>>>>>>>> - rebase
>>>>>>>> - rework to use generic PCI-IOMMU bindings instead of generic
>>>>>>>> IOMMU bindings
>>>>>>>>
>>>>>>>> Previous discussion is at:
>>>>>>>> https://urldefense.com/v3/__https://lore.kernel.org/xen-devel/20221006174804.2003029-1-olekstysh@gmail.com/__;!!GF_29dbcQIUBPA!3-vq7Edm3XfKtD5cnNjnOzDQvuo_XrhJ73yH-nPfqOkGGU0IjLG7R7MR_nAJCAPeOutHRLT44wKYwQwz3SauACie_ZAy$
>>>>>>>>
>>>>>>>>
>>>>>>>> [lore[.]kernel[.]org]
>>>>>>>>
>>>>>>>> Based on:
>>>>>>>> https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git/log/?h=for-linus-6.1__;!!GF_29dbcQIUBPA!3-vq7Edm3XfKtD5cnNjnOzDQvuo_XrhJ73yH-nPfqOkGGU0IjLG7R7MR_nAJCAPeOutHRLT44wKYwQwz3SauAEnMDHAq$
>>>>>>>>
>>>>>>>>
>>>>>>>> [git[.]kernel[.]org]
>>>>>>>> ---
>>>>>>>> drivers/xen/grant-dma-ops.c | 87
>>>>>>>> ++++++++++++++++++++++++++++++++-----
>>>>>>>> 1 file changed, 76 insertions(+), 11 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/xen/grant-dma-ops.c
>>>>>>>> b/drivers/xen/grant-dma-ops.c
>>>>>>>> index daa525df7bdc..b79d9d6ce154 100644
>>>>>>>> --- a/drivers/xen/grant-dma-ops.c
>>>>>>>> +++ b/drivers/xen/grant-dma-ops.c
>>>>>>>> @@ -10,6 +10,7 @@
>>>>>>>> #include <linux/module.h>
>>>>>>>> #include <linux/dma-map-ops.h>
>>>>>>>> #include <linux/of.h>
>>>>>>>> +#include <linux/pci.h>
>>>>>>>> #include <linux/pfn.h>
>>>>>>>> #include <linux/xarray.h>
>>>>>>>> #include <linux/virtio_anchor.h>
>>>>>>>> @@ -292,12 +293,55 @@ static const struct dma_map_ops
>>>>>>>> xen_grant_dma_ops = {
>>>>>>>> .dma_supported = xen_grant_dma_supported,
>>>>>>>> };
>>>>>>>> +static struct device_node *xen_dt_get_pci_host_node(struct
>>>>>>>> device
>>>>>>>> *dev)
>>>>>>>> +{
>>>>>>>> + struct pci_dev *pdev = to_pci_dev(dev);
>>>>>>>> + struct pci_bus *bus = pdev->bus;
>>>>>>>> +
>>>>>>>> + /* Walk up to the root bus to look for PCI Host controller */
>>>>>>>> + while (!pci_is_root_bus(bus))
>>>>>>>> + bus = bus->parent;
>>>>>>>> +
>>>>>>>> + return of_node_get(bus->bridge->parent->of_node);
>>>>>>>> +}
>>>>>>>
>>>>>>> It seems silly that we need to walk the hierachy that way, but I
>>>>>>> couldn't find another way to do it
>>>>>>>
>>>>>>>
>>>>>>>> +static struct device_node *xen_dt_get_node(struct device *dev)
>>>>>>>> +{
>>>>>>>> + if (dev_is_pci(dev))
>>>>>>>> + return xen_dt_get_pci_host_node(dev);
>>>>>>>> +
>>>>>>>> + return of_node_get(dev->of_node);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static int xen_dt_map_id(struct device *dev, struct device_node
>>>>>>>> **iommu_np,
>>>>>>>> + u32 *sid)
>>>>>>>> +{
>>>>>>>> + struct pci_dev *pdev = to_pci_dev(dev);
>>>>>>>> + u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
>>>>>>>> + struct device_node *host_np;
>>>>>>>> + int ret;
>>>>>>>> +
>>>>>>>> + host_np = xen_dt_get_pci_host_node(dev);
>>>>>>>> + if (!host_np)
>>>>>>>> + return -ENODEV;
>>>>>>>> +
>>>>>>>> + ret = of_map_id(host_np, rid, "iommu-map", "iommu-map-mask",
>>>>>>>> iommu_np, sid);
>>>>>>>> + of_node_put(host_np);
>>>>>>>> + return ret;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> static bool xen_is_dt_grant_dma_device(struct device *dev)
>>>>>>>> {
>>>>>>>> - struct device_node *iommu_np;
>>>>>>>> + struct device_node *iommu_np = NULL;
>>>>>>>> bool has_iommu;
>>>>>>>> - iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>>>>>> + if (dev_is_pci(dev)) {
>>>>>>>> + if (xen_dt_map_id(dev, &iommu_np, NULL))
>>>>>>>> + return false;
>>>>>>>> + } else
>>>>>>>> + iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>>>>>> +
>>>>>>>> has_iommu = iommu_np &&
>>>>>>>> of_device_is_compatible(iommu_np, "xen,grant-dma");
>>>>>>>> of_node_put(iommu_np);
>>>>>>>> @@ -307,9 +351,17 @@ static bool xen_is_dt_grant_dma_device(struct
>>>>>>>> device *dev)
>>>>>>>> bool xen_is_grant_dma_device(struct device *dev)
>>>>>>>> {
>>>>>>>> + struct device_node *np;
>>>>>>>> +
>>>>>>>> /* XXX Handle only DT devices for now */
>>>>>>>> - if (dev->of_node)
>>>>>>>> - return xen_is_dt_grant_dma_device(dev);
>>>>>>>> + np = xen_dt_get_node(dev);
>>>>>>>> + if (np) {
>>>>>>>> + bool ret;
>>>>>>>> +
>>>>>>>> + ret = xen_is_dt_grant_dma_device(dev);
>>>>>>>> + of_node_put(np);
>>>>>>>> + return ret;
>>>>>>>> + }
>>>>>>>
>>>>>>> We don't need to walk the PCI hierachy twice. Maybe we can add the
>>>>>>> of_node check directly to xen_is_dt_grant_dma_device?
>>>>>>>
>>>>>>
>>>>>> I think in general we could pass directly the host bridge device if
>>>>>> dev_is_pci(dev) (which can be retrieved with
>>>>>> pci_get_host_bridge_device(to_pci_dev(dev), and after done with it
>>>>>> pci_put_host_bridge_device(phb)).
>>>>>> So that, xen_is_dt_grant_dma_device() and
>>>>>> xen_dt_grant_init_backend_domid() won't need to discover it
>>>>>> themselves.
>>>>>> This will simplify the code.
>>>>>
>>>>>
>>>>> Good point. I have some remark. Can we use pci_find_host_bridge()
>>>>> instead? This way we don't have to add #include "../pci/pci.h", and
>>>>> have
>>>>> to drop reference afterwards.
>>>>>
>>>>> With that xen_dt_get_pci_host_node() will became the following:
>>>>>
>>>>>
>>>>> static struct device_node *xen_dt_get_pci_host_node(struct device
>>>>> *dev)
>>>>> {
>>>>> struct pci_host_bridge *bridge =
>>>>> pci_find_host_bridge(to_pci_dev(dev)->bus);
>>>>>
>>>>> return of_node_get(bridge->dev.parent->of_node);
>>>>> }
>>>>>
>>>>
>>>> You are right. I prefer your version instead of the above.
>>>
>>>
>>> ok, thanks
>>>
>>>
>>>>
>>>>
>>>>>
>>>>> With Stefano's suggestion, we won't walk the PCI hierarchy twice when
>>>>> executing xen_is_grant_dma_device() for PCI device:
>>>>>
>>>>> xen_is_grant_dma_device() -> xen_is_dt_grant_dma_device() ->
>>>>> xen_dt_map_id() -> xen_dt_get_pci_host_node()
>>>>>
>>>>>
>>>>> What do you think?
>>>>>
>>>>
>>>> I was thinking passing the device_node along with the device in the
>>>> function arguments. More specifically, of doing this (not tested, just
>>>> an idea):
>>>>
>>>> bool xen_is_grant_dma_device(struct device *dev)
>>>> {
>>>> struct device_node *np;
>>>> bool has_iommu = false;
>>>>
>>>> /* XXX Handle only DT devices for now */
>>>> np = xen_dt_get_node(dev);
>>>> if (np)
>>>> has_iommu = xen_is_dt_grant_dma_device(dev, np);
>>>> of_node_put(np);
>>>> return has_iommu;
>>>> }
>>>>
>>>> static bool xen_is_dt_grant_dma_device(struct device *dev,
>>>> struct device_node *np)
>>>> {
>>>> struct device_node *iommu_np = NULL;
>>>> bool has_iommu;
>>>>
>>>> if (dev_is_pci(dev)) {
>>>> struct pci_dev *pdev = to_pci_dev(dev);
>>>> u32 id = PCI_DEVID(pdev->bus->number, pdev->devfn);
>>>> of_map_id(np, id, "iommu-map", "iommu-map-mask", &iommu_np,
>>>> NULL);
>>>> } else {
>>>> iommu_np = of_parse_phandle(np, "iommus", 0);
>>>> }
>>>>
>>>> has_iommu = iommu_np && of_device_is_compatible(iommu_np,
>>>> "xen,grant-dma");
>>>> of_node_put(iommu_np);
>>>>
>>>> return has_iommu;
>>>> }
>>>
>>>
>>> I got it.
>>>
>>> xen_is_grant_dma_device() for V3 won't call xen_dt_get_node(), but call
>>> xen_is_dt_grant_dma_device() directly.
>>>
>>> static bool xen_is_dt_grant_dma_device(struct device *dev)
>>> {
>>> struct device_node *iommu_np = NULL;
>>> bool has_iommu;
>>>
>>> if (dev_is_pci(dev)) {
>>> if (xen_dt_map_id(dev, &iommu_np, NULL))
>>> return false;
>>> } else if (dev->of_node)
>>> iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>> else
>>> return false;
>>>
>>> has_iommu = iommu_np &&
>>> of_device_is_compatible(iommu_np, "xen,grant-dma");
>>> of_node_put(iommu_np);
>>>
>>> return has_iommu;
>>> }
>>>
>>> bool xen_is_grant_dma_device(struct device *dev)
>>> {
>>> /* XXX Handle only DT devices for now */
>>> return xen_is_dt_grant_dma_device(dev);
>>> }
>>>
>>>
>>
>> Ok. One difference, that I see from the previous, is that here you
>> don't use the dynamic interface when you access the dev->of_node
>> (of_node_get/of_node_put). Before, this was guarded through the
>> external xen_dt_get_node().
>>
>> I suspect that the same needs to be done for the function
>> xen_grant_setup_dma_ops(). There, also, the code walks up to the root
>> bus twice.
>
>
> Hmm, xen_dt_grant_init_backend_domid() should only be called if we deal
> with device-tree based device.
>
> I think you are completely right, thanks!
>
> In order to address both your comments, I think I need to rework the
> code (taking into the account your example with xen_is_dt_grant_dma_device()
>
> provided a few letters ago and extrapolate this example to
> xen_dt_grant_init_backend_domid()). Below the patch (not tested) which
> seems to address both your comments (also I dropped
>
> xen_dt_map_id() and squashed xen_dt_get_pci_host_node() with
> xen_dt_get_node()).
>
>
> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> index daa525df7bdc..dae24dbd2ef7 100644
> --- a/drivers/xen/grant-dma-ops.c
> +++ b/drivers/xen/grant-dma-ops.c
> @@ -10,6 +10,7 @@
> #include <linux/module.h>
> #include <linux/dma-map-ops.h>
> #include <linux/of.h>
> +#include <linux/pci.h>
> #include <linux/pfn.h>
> #include <linux/xarray.h>
> #include <linux/virtio_anchor.h>
> @@ -292,12 +293,33 @@ static const struct dma_map_ops xen_grant_dma_ops = {
> .dma_supported = xen_grant_dma_supported,
> };
>
> -static bool xen_is_dt_grant_dma_device(struct device *dev)
> +static struct device_node *xen_dt_get_node(struct device *dev)
> {
> - struct device_node *iommu_np;
> + if (dev_is_pci(dev)) {
> + struct pci_dev *pdev = to_pci_dev(dev);
> + struct pci_host_bridge *bridge =
> pci_find_host_bridge(pdev->bus);
> +
> + return of_node_get(bridge->dev.parent->of_node);
> + }
> +
> + return of_node_get(dev->of_node);
> +}
> +
It does not seem right to me to expose the struct pci_host_bridge (which
we would need to check if it is null by the way). I would prefer your
version for the above i.e
static struct device_node *xen_dt_get_node(struct device *dev)
{
if (dev_is_pci(dev)) {
struct pci_bus *bus = to_pci_dev(dev)->bus;
/* Walk up to the root bus to look for PCI Host controller */
while (!pci_is_root_bus(bus))
bus = bus->parent;
return of_node_get(bus->bridge->parent->of_node);
}
return of_node_get(dev->of_node);
}
> +static bool xen_is_dt_grant_dma_device(struct device *dev,
> + struct device_node *np)
> +{
> + struct device_node *iommu_np = NULL;
> bool has_iommu;
>
> - iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
> + if (dev_is_pci(dev)) {
> + struct pci_dev *pdev = to_pci_dev(dev);
> + u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
> +
> + if (of_map_id(np, rid, "iommu-map", "iommu-map-mask",
> &iommu_np, NULL))
> + return false;
> + } else
> + iommu_np = of_parse_phandle(np, "iommus", 0);
> +
> has_iommu = iommu_np &&
> of_device_is_compatible(iommu_np, "xen,grant-dma");
> of_node_put(iommu_np);
> @@ -307,9 +329,17 @@ static bool xen_is_dt_grant_dma_device(struct
> device *dev)
>
> bool xen_is_grant_dma_device(struct device *dev)
> {
> + struct device_node *np;
> +
> /* XXX Handle only DT devices for now */
> - if (dev->of_node)
> - return xen_is_dt_grant_dma_device(dev);
> + np = xen_dt_get_node(dev);
> + if (np) {
> + bool ret;
> +
> + ret = xen_is_dt_grant_dma_device(dev, np);
> + of_node_put(np);
> + return ret;
> + }
>
> return false;
> }
> @@ -323,14 +353,26 @@ bool xen_virtio_mem_acc(struct virtio_device *dev)
> }
>
> static int xen_dt_grant_init_backend_domid(struct device *dev,
> + struct device_node *np,
> struct xen_grant_dma_data *data)
> {
> - struct of_phandle_args iommu_spec;
> + struct of_phandle_args iommu_spec = { .args_count = 1 };
>
> - if (of_parse_phandle_with_args(dev->of_node, "iommus",
> "#iommu-cells",
> - 0, &iommu_spec)) {
> - dev_err(dev, "Cannot parse iommus property\n");
> - return -ESRCH;
> + if (dev_is_pci(dev)) {
> + struct pci_dev *pdev = to_pci_dev(dev);
> + u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
> +
> + if (of_map_id(np, rid, "iommu-map", "iommu-map-mask",
> &iommu_spec.np,
> + iommu_spec.args)) {
> + dev_err(dev, "Cannot translate ID\n");
> + return -ESRCH;
> + }
> + } else {
> + if (of_parse_phandle_with_args(np, "iommus", "#iommu-cells",
> + 0, &iommu_spec)) {
> + dev_err(dev, "Cannot parse iommus property\n");
> + return -ESRCH;
> + }
> }
>
IMO, instead of passing struct xen_grant_dma_data *data to
xen_dt_grant_init_backend_domid(), you could pass domid_t *backend_domid
(e.g xen_dt_grant_init_backend_domid(dev, np, &data->backend_domid)).
I think this way the internal struct xen_grant_dma_datain is manipulated
in a single place and xen_dt_grant_init_backend_domid() does not depend
on it.
> if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
> @@ -354,6 +396,7 @@ static int xen_dt_grant_init_backend_domid(struct
> device *dev,
> void xen_grant_setup_dma_ops(struct device *dev)
> {
> struct xen_grant_dma_data *data;
> + struct device_node *np;
>
> data = find_xen_grant_dma_data(dev);
> if (data) {
> @@ -365,8 +408,13 @@ void xen_grant_setup_dma_ops(struct device *dev)
> if (!data)
> goto err;
>
> - if (dev->of_node) {
> - if (xen_dt_grant_init_backend_domid(dev, data))
> + np = xen_dt_get_node(dev);
> + if (np) {
> + int ret;
> +
> + ret = xen_dt_grant_init_backend_domid(dev, np, data);
> + of_node_put(np);
> + if (ret)
> goto err;
> } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
> dev_info(dev, "Using dom0 as backend\n");
>
>
> Does it look ok now?
That is what I had in mind. I do not know if Stefano agrees with this
approach.
>>
>>
>>>>
>>>> I 'm wondering ... is it possible for the host bridge device node to
>>>> have the iommus property set? meaning that all of its pci devs will
>>>> have the same backend?
>>>
>>> Good question. I think, it is possible... This is technically what V1 is
>>> doing.
>>>
>>>
>>> Are you asking because to support "iommus" for PCI devices as well to
>>> describe that use-case with all PCI devices having the same endpoint ID
>>> (backend ID)?
>>> If yes, I think, this could be still described by "iommu-map" property,
>>> something like that (if we don't want to describe mapping for each PCI
>>> device one-by-one).
>>>
>>> iommu-map = <0x0 &iommu X 0x1>;
>>>
>>> iommu-map-mask = <0x0>;
>>>
>>> where the X is backend ID.
>>>
>>>
>>> It feels to me that it should be written down somewhere that for
>>> platform devices we expect "iommus" and for PCI devices we expect
>>> "iommu-map/iommu-map-mask" to be present.
>>
>> Thanks for the clarification, now I got it. Yes I agree.
>
>
> ok, good
>
>
>>
>>>>
>>>>
>>>>>>
>>>>>>>
>>>>>>>> return false;
>>>>>>>> }
>>>>>>>> @@ -325,12 +377,19 @@ bool xen_virtio_mem_acc(struct virtio_device
>>>>>>>> *dev)
>>>>>>>> static int xen_dt_grant_init_backend_domid(struct device *dev,
>>>>>>>> struct xen_grant_dma_data *data)
>>>>>>>> {
>>>>>>>> - struct of_phandle_args iommu_spec;
>>>>>>>> + struct of_phandle_args iommu_spec = { .args_count = 1 };
>>>>>>>> - if (of_parse_phandle_with_args(dev->of_node, "iommus",
>>>>>>>> "#iommu-cells",
>>>>>>>> - 0, &iommu_spec)) {
>>>>>>>> - dev_err(dev, "Cannot parse iommus property\n");
>>>>>>>> - return -ESRCH;
>>>>>>>> + if (dev_is_pci(dev)) {
>>>>>>>> + if (xen_dt_map_id(dev, &iommu_spec.np, iommu_spec.args)) {
>>>>>>>> + dev_err(dev, "Cannot translate ID\n");
>>>>>>>> + return -ESRCH;
>>>>>>>> + }
>>>>>>>> + } else {
>>>>>>>> + if (of_parse_phandle_with_args(dev->of_node, "iommus",
>>>>>>>> "#iommu-cells",
>>>>>>>> + 0, &iommu_spec)) {
>>>>>>>> + dev_err(dev, "Cannot parse iommus property\n");
>>>>>>>> + return -ESRCH;
>>>>>>>> + }
>>>>>>>> }
>>>>>>>> if (!of_device_is_compatible(iommu_spec.np,
>>>>>>>> "xen,grant-dma") ||
>>>>>>>> @@ -354,6 +413,7 @@ static int
>>>>>>>> xen_dt_grant_init_backend_domid(struct device *dev,
>>>>>>>> void xen_grant_setup_dma_ops(struct device *dev)
>>>>>>>> {
>>>>>>>> struct xen_grant_dma_data *data;
>>>>>>>> + struct device_node *np;
>>>>>>>> data = find_xen_grant_dma_data(dev);
>>>>>>>> if (data) {
>>>>>>>> @@ -365,8 +425,13 @@ void xen_grant_setup_dma_ops(struct device
>>>>>>>> *dev)
>>>>>>>> if (!data)
>>>>>>>> goto err;
>>>>>>>> - if (dev->of_node) {
>>>>>>>> - if (xen_dt_grant_init_backend_domid(dev, data))
>>>>>>>> + np = xen_dt_get_node(dev);
>>>>>>>> + if (np) {
>>>>>>>> + int ret;
>>>>>>>> +
>>>>>>>> + ret = xen_dt_grant_init_backend_domid(dev, data);
>>>>>>>> + of_node_put(np);
>>>>>>>> + if (ret)
>>>>>>>> goto err;
>>>>>>>> } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
>>>>>>>> dev_info(dev, "Using dom0 as backend\n");
>>>>>>>> --
>>>>>>>> 2.25.1
>>>>>>>>
>>>>>>>
>>>>>>
>>>>
>>
--
Xenia
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