[PATCH 0/3] xen/virtio: support grant based virtio on x86

[PATCH 0/3] xen/virtio: support grant based virtio on x86

[Juergen Gross]

Add basic support for virtio with grants on x86 by defaulting the
backend to be in dom0 in the case the guest kernel was built with
CONFIG_XEN_VIRTIO_FORCE_GRANT.

Juergen Gross (3):
  xen/virtio: restructure xen grant dma setup
  xen/virtio: use dom0 as default backend for
    CONFIG_XEN_VIRTIO_FORCE_GRANT
  xen/virtio: enable grant based virtio on x86

 arch/x86/xen/enlighten_hvm.c |  2 +-
 arch/x86/xen/enlighten_pv.c  |  2 +-
 drivers/xen/grant-dma-ops.c  | 81 +++++++++++++++++++++++++-----------
 include/xen/xen-ops.h        |  1 +
 4 files changed, 59 insertions(+), 27 deletions(-)

-- 
2.35.3

[PATCH 1/3] xen/virtio: restructure xen grant dma setup

[Juergen Gross]

In order to prepare supporting other means than device tree for
setting up virtio devices under Xen, restructure the functions
xen_is_grant_dma_device() and xen_grant_setup_dma_ops() a little bit.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/xen/grant-dma-ops.c | 68 +++++++++++++++++++++++--------------
 1 file changed, 43 insertions(+), 25 deletions(-)

diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index 8973fc1e9ccc..f29759d5301f 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -273,22 +273,28 @@ static const struct dma_map_ops xen_grant_dma_ops = {
 	.dma_supported = xen_grant_dma_supported,
 };
 
-bool xen_is_grant_dma_device(struct device *dev)
+static bool xen_is_dt_grant_dma_device(struct device *dev)
 {
 	struct device_node *iommu_np;
 	bool has_iommu;
 
-	/* XXX Handle only DT devices for now */
-	if (!dev->of_node)
-		return false;
-
 	iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
-	has_iommu = iommu_np && of_device_is_compatible(iommu_np, "xen,grant-dma");
+	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 */
+	if (dev->of_node)
+		return xen_is_dt_grant_dma_device(dev);
+
+	return false;
+}
+
 bool xen_virtio_mem_acc(struct virtio_device *dev)
 {
 	if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
@@ -297,45 +303,56 @@ bool xen_virtio_mem_acc(struct virtio_device *dev)
 	return xen_is_grant_dma_device(dev->dev.parent);
 }
 
-void xen_grant_setup_dma_ops(struct device *dev)
+static int xen_dt_grant_setup_dma_ops(struct device *dev,
+				       struct xen_grant_dma_data *data)
 {
-	struct xen_grant_dma_data *data;
 	struct of_phandle_args iommu_spec;
 
-	data = find_xen_grant_dma_data(dev);
-	if (data) {
-		dev_err(dev, "Xen grant DMA data is already created\n");
-		return;
-	}
-
-	/* XXX ACPI device unsupported for now */
-	if (!dev->of_node)
-		goto err;
-
 	if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells",
 			0, &iommu_spec)) {
 		dev_err(dev, "Cannot parse iommus property\n");
-		goto err;
+		return -ESRCH;
 	}
 
 	if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
 			iommu_spec.args_count != 1) {
 		dev_err(dev, "Incompatible IOMMU node\n");
 		of_node_put(iommu_spec.np);
-		goto err;
+		return -ESRCH;
 	}
 
 	of_node_put(iommu_spec.np);
 
+	/*
+	 * The endpoint ID here means the ID of the domain where the
+	 * corresponding backend is running
+	 */
+	data->backend_domid = iommu_spec.args[0];
+
+	return 0;
+}
+
+void xen_grant_setup_dma_ops(struct device *dev)
+{
+	struct xen_grant_dma_data *data;
+
+	data = find_xen_grant_dma_data(dev);
+	if (data) {
+		dev_err(dev, "Xen grant DMA data is already created\n");
+		return;
+	}
+
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		goto err;
 
-	/*
-	 * The endpoint ID here means the ID of the domain where the corresponding
-	 * backend is running
-	 */
-	data->backend_domid = iommu_spec.args[0];
+	if (dev->of_node) {
+		if (xen_dt_grant_setup_dma_ops(dev, data))
+			goto err;
+	} else {
+		/* XXX ACPI device unsupported for now */
+		goto err;
+	}
 
 	if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data,
 			GFP_KERNEL))) {
@@ -348,6 +365,7 @@ void xen_grant_setup_dma_ops(struct device *dev)
 	return;
 
 err:
+	devm_kfree(dev, data);
 	dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
 }
 
-- 
2.35.3

[PATCH 2/3] xen/virtio: use dom0 as default backend for CONFIG_XEN_VIRTIO_FORCE_GRANT

[Juergen Gross]

With CONFIG_XEN_VIRTIO_FORCE_GRANT set the default backend domid to 0,
enabling to use xen_grant_dma_ops for those devices.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/xen/grant-dma-ops.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index f29759d5301f..a00112235877 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -349,6 +349,9 @@ void xen_grant_setup_dma_ops(struct device *dev)
 	if (dev->of_node) {
 		if (xen_dt_grant_setup_dma_ops(dev, data))
 			goto err;
+	} else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
+		dev_info(dev, "Using dom0 as backend\n");
+		data->backend_domid = 0;
 	} else {
 		/* XXX ACPI device unsupported for now */
 		goto err;
-- 
2.35.3

[PATCH 3/3] xen/virtio: enable grant based virtio on x86

[Juergen Gross]

Use an x86-specific virtio_check_mem_acc_cb() for Xen in order to setup
the correct DMA ops.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/xen/enlighten_hvm.c |  2 +-
 arch/x86/xen/enlighten_pv.c  |  2 +-
 drivers/xen/grant-dma-ops.c  | 10 ++++++++++
 include/xen/xen-ops.h        |  1 +
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index 1c1ac418484b..c1cd28e915a3 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -212,7 +212,7 @@ static void __init xen_hvm_guest_init(void)
 		return;
 
 	if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
-		virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
+		virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
 
 	init_hvm_pv_info();
 
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 9b1a58dda935..45b24c1b646a 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -112,7 +112,7 @@ static void __init xen_pv_init_platform(void)
 {
 	/* PV guests can't operate virtio devices without grants. */
 	if (IS_ENABLED(CONFIG_XEN_VIRTIO))
-		virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
+		virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
 
 	populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));
 
diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index a00112235877..60a7acc334ed 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -372,6 +372,16 @@ void xen_grant_setup_dma_ops(struct device *dev)
 	dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
 }
 
+bool xen_virtio_restricted_mem_acc(struct virtio_device *dev)
+{
+	bool ret = xen_virtio_mem_acc(dev);
+
+	if (ret)
+		xen_grant_setup_dma_ops(dev->dev.parent);
+
+	return ret;
+}
+
 MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
 MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
 MODULE_LICENSE("GPL");
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index dae0f350c678..3dd5aa936f1d 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -219,6 +219,7 @@ static inline void xen_preemptible_hcall_end(void) { }
 void xen_grant_setup_dma_ops(struct device *dev);
 bool xen_is_grant_dma_device(struct device *dev);
 bool xen_virtio_mem_acc(struct virtio_device *dev);
+bool xen_virtio_restricted_mem_acc(struct virtio_device *dev);
 #else
 static inline void xen_grant_setup_dma_ops(struct device *dev)
 {
-- 
2.35.3

Re: [PATCH 3/3] xen/virtio: enable grant based virtio on x86

[Oleksandr Tyshchenko]

On 06.10.22 10:15, Juergen Gross wrote:


Hello Juergen

> Use an x86-specific virtio_check_mem_acc_cb() for Xen in order to setup
> the correct DMA ops.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
>   arch/x86/xen/enlighten_hvm.c |  2 +-
>   arch/x86/xen/enlighten_pv.c  |  2 +-
>   drivers/xen/grant-dma-ops.c  | 10 ++++++++++
>   include/xen/xen-ops.h        |  1 +
>   4 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
> index 1c1ac418484b..c1cd28e915a3 100644
> --- a/arch/x86/xen/enlighten_hvm.c
> +++ b/arch/x86/xen/enlighten_hvm.c
> @@ -212,7 +212,7 @@ static void __init xen_hvm_guest_init(void)
>   		return;
>   
>   	if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
> -		virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
> +		virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
>   
>   	init_hvm_pv_info();
>   
> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> index 9b1a58dda935..45b24c1b646a 100644
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -112,7 +112,7 @@ static void __init xen_pv_init_platform(void)
>   {
>   	/* PV guests can't operate virtio devices without grants. */
>   	if (IS_ENABLED(CONFIG_XEN_VIRTIO))
> -		virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
> +		virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
>   
>   	populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));
>   
> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> index a00112235877..60a7acc334ed 100644
> --- a/drivers/xen/grant-dma-ops.c
> +++ b/drivers/xen/grant-dma-ops.c
> @@ -372,6 +372,16 @@ void xen_grant_setup_dma_ops(struct device *dev)
>   	dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
>   }
>   
> +bool xen_virtio_restricted_mem_acc(struct virtio_device *dev)
> +{
> +	bool ret = xen_virtio_mem_acc(dev);


The grant usage is mandatory for PV guests, right?

Then xen_virtio_mem_acc() should always return true for PV guests (I 
mean even if CONFIG_XEN_VIRTIO_FORCE_GRANT is not set).



> +
> +	if (ret)
> +		xen_grant_setup_dma_ops(dev->dev.parent);
> +
> +	return ret;
> +}
> +
>   MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
>   MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
>   MODULE_LICENSE("GPL");
> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
> index dae0f350c678..3dd5aa936f1d 100644
> --- a/include/xen/xen-ops.h
> +++ b/include/xen/xen-ops.h
> @@ -219,6 +219,7 @@ static inline void xen_preemptible_hcall_end(void) { }
>   void xen_grant_setup_dma_ops(struct device *dev);
>   bool xen_is_grant_dma_device(struct device *dev);
>   bool xen_virtio_mem_acc(struct virtio_device *dev);
> +bool xen_virtio_restricted_mem_acc(struct virtio_device *dev);
>   #else
>   static inline void xen_grant_setup_dma_ops(struct device *dev)
>   {


And probably static inline stub always returning false if 
CONFIG_XEN_GRANT_DMA_OPS is not set.


-- 
Regards,

Oleksandr Tyshchenko

Re: [PATCH 1/3] xen/virtio: restructure xen grant dma setup

[Oleksandr Tyshchenko]

On 06.10.22 10:14, Juergen Gross wrote:

Hello Juergen

> In order to prepare supporting other means than device tree for
> setting up virtio devices under Xen, restructure the functions
> xen_is_grant_dma_device() and xen_grant_setup_dma_ops() a little bit.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>


Patch looks good,

one NIT, xen_dt_grant_setup_dma_ops() down the code doesn't actually 
setup DMA OPS, it retrieves the backend domid via device-tree means and 
stores it,

so I would rename to it, maybe something like 
xen_dt_grant_setup_backend_domid() or xen_dt_grant_init_backend_domid(), 
but I am not sure it would be good alternative.


So, w/ or w/o renaming:

Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

also

Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 
only


> ---
>   drivers/xen/grant-dma-ops.c | 68 +++++++++++++++++++++++--------------
>   1 file changed, 43 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> index 8973fc1e9ccc..f29759d5301f 100644
> --- a/drivers/xen/grant-dma-ops.c
> +++ b/drivers/xen/grant-dma-ops.c
> @@ -273,22 +273,28 @@ static const struct dma_map_ops xen_grant_dma_ops = {
>   	.dma_supported = xen_grant_dma_supported,
>   };
>   
> -bool xen_is_grant_dma_device(struct device *dev)
> +static bool xen_is_dt_grant_dma_device(struct device *dev)
>   {
>   	struct device_node *iommu_np;
>   	bool has_iommu;
>   
> -	/* XXX Handle only DT devices for now */
> -	if (!dev->of_node)
> -		return false;
> -
>   	iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
> -	has_iommu = iommu_np && of_device_is_compatible(iommu_np, "xen,grant-dma");
> +	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 */
> +	if (dev->of_node)
> +		return xen_is_dt_grant_dma_device(dev);
> +
> +	return false;
> +}
> +
>   bool xen_virtio_mem_acc(struct virtio_device *dev)
>   {
>   	if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
> @@ -297,45 +303,56 @@ bool xen_virtio_mem_acc(struct virtio_device *dev)
>   	return xen_is_grant_dma_device(dev->dev.parent);
>   }
>   
> -void xen_grant_setup_dma_ops(struct device *dev)
> +static int xen_dt_grant_setup_dma_ops(struct device *dev,
> +				       struct xen_grant_dma_data *data)
>   {
> -	struct xen_grant_dma_data *data;
>   	struct of_phandle_args iommu_spec;
>   
> -	data = find_xen_grant_dma_data(dev);
> -	if (data) {
> -		dev_err(dev, "Xen grant DMA data is already created\n");
> -		return;
> -	}
> -
> -	/* XXX ACPI device unsupported for now */
> -	if (!dev->of_node)
> -		goto err;
> -
>   	if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells",
>   			0, &iommu_spec)) {
>   		dev_err(dev, "Cannot parse iommus property\n");
> -		goto err;
> +		return -ESRCH;
>   	}
>   
>   	if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
>   			iommu_spec.args_count != 1) {
>   		dev_err(dev, "Incompatible IOMMU node\n");
>   		of_node_put(iommu_spec.np);
> -		goto err;
> +		return -ESRCH;
>   	}
>   
>   	of_node_put(iommu_spec.np);
>   
> +	/*
> +	 * The endpoint ID here means the ID of the domain where the
> +	 * corresponding backend is running
> +	 */
> +	data->backend_domid = iommu_spec.args[0];
> +
> +	return 0;
> +}
> +
> +void xen_grant_setup_dma_ops(struct device *dev)
> +{
> +	struct xen_grant_dma_data *data;
> +
> +	data = find_xen_grant_dma_data(dev);
> +	if (data) {
> +		dev_err(dev, "Xen grant DMA data is already created\n");
> +		return;
> +	}
> +
>   	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>   	if (!data)
>   		goto err;
>   
> -	/*
> -	 * The endpoint ID here means the ID of the domain where the corresponding
> -	 * backend is running
> -	 */
> -	data->backend_domid = iommu_spec.args[0];
> +	if (dev->of_node) {
> +		if (xen_dt_grant_setup_dma_ops(dev, data))
> +			goto err;
> +	} else {
> +		/* XXX ACPI device unsupported for now */
> +		goto err;
> +	}
>   
>   	if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data,
>   			GFP_KERNEL))) {
> @@ -348,6 +365,7 @@ void xen_grant_setup_dma_ops(struct device *dev)
>   	return;
>   
>   err:
> +	devm_kfree(dev, data);
>   	dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
>   }
>   

-- 
Regards,

Oleksandr Tyshchenko

Re: [PATCH 2/3] xen/virtio: use dom0 as default backend for CONFIG_XEN_VIRTIO_FORCE_GRANT

[Oleksandr Tyshchenko]

On 06.10.22 10:14, Juergen Gross wrote:

Hello Juergen

> With CONFIG_XEN_VIRTIO_FORCE_GRANT set the default backend domid to 0,
> enabling to use xen_grant_dma_ops for those devices.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
>   drivers/xen/grant-dma-ops.c | 3 +++
>   1 file changed, 3 insertions(+)


Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

>
> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> index f29759d5301f..a00112235877 100644
> --- a/drivers/xen/grant-dma-ops.c
> +++ b/drivers/xen/grant-dma-ops.c
> @@ -349,6 +349,9 @@ void xen_grant_setup_dma_ops(struct device *dev)
>   	if (dev->of_node) {
>   		if (xen_dt_grant_setup_dma_ops(dev, data))
>   			goto err;
> +	} else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
> +		dev_info(dev, "Using dom0 as backend\n");
> +		data->backend_domid = 0;
>   	} else {
>   		/* XXX ACPI device unsupported for now */
>   		goto err;

-- 
Regards,

Oleksandr Tyshchenko

Re: [PATCH 1/3] xen/virtio: restructure xen grant dma setup

[Stefano Stabellini]

On Thu, 6 Oct 2022, Oleksandr Tyshchenko wrote:
> On 06.10.22 10:14, Juergen Gross wrote:
> 
> Hello Juergen
> 
> > In order to prepare supporting other means than device tree for
> > setting up virtio devices under Xen, restructure the functions
> > xen_is_grant_dma_device() and xen_grant_setup_dma_ops() a little bit.
> >
> > Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> 
> Patch looks good,
> 
> one NIT, xen_dt_grant_setup_dma_ops() down the code doesn't actually 
> setup DMA OPS, it retrieves the backend domid via device-tree means and 
> stores it,
> 
> so I would rename to it, maybe something like 
> xen_dt_grant_setup_backend_domid() or xen_dt_grant_init_backend_domid(), 
> but I am not sure it would be good alternative.
> 
> 
> So, w/ or w/o renaming:
> 
> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> also
> 
> Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 
> only

Acked-by: Stefano Stabellini <sstabellini@kernel.org>

Re: [PATCH 2/3] xen/virtio: use dom0 as default backend for CONFIG_XEN_VIRTIO_FORCE_GRANT

[Stefano Stabellini]

On Thu, 6 Oct 2022, Oleksandr Tyshchenko wrote:
> On 06.10.22 10:14, Juergen Gross wrote:
> 
> Hello Juergen
> 
> > With CONFIG_XEN_VIRTIO_FORCE_GRANT set the default backend domid to 0,
> > enabling to use xen_grant_dma_ops for those devices.
> >
> > Signed-off-by: Juergen Gross <jgross@suse.com>
> > ---
> >   drivers/xen/grant-dma-ops.c | 3 +++
> >   1 file changed, 3 insertions(+)
> 
> 
> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

Acked-by: Stefano Stabellini <sstabellini@kernel.org>


> > diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> > index f29759d5301f..a00112235877 100644
> > --- a/drivers/xen/grant-dma-ops.c
> > +++ b/drivers/xen/grant-dma-ops.c
> > @@ -349,6 +349,9 @@ void xen_grant_setup_dma_ops(struct device *dev)
> >   	if (dev->of_node) {
> >   		if (xen_dt_grant_setup_dma_ops(dev, data))
> >   			goto err;
> > +	} else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
> > +		dev_info(dev, "Using dom0 as backend\n");
> > +		data->backend_domid = 0;
> >   	} else {
> >   		/* XXX ACPI device unsupported for now */
> >   		goto err;
> 
> -- 
> Regards,
> 
> Oleksandr Tyshchenko
> 

Re: [PATCH 3/3] xen/virtio: enable grant based virtio on x86

[Juergen Gross]

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On 06.10.22 18:04, Oleksandr Tyshchenko wrote:
> 
> On 06.10.22 10:15, Juergen Gross wrote:
> 
> 
> Hello Juergen
> 
>> Use an x86-specific virtio_check_mem_acc_cb() for Xen in order to setup
>> the correct DMA ops.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>>    arch/x86/xen/enlighten_hvm.c |  2 +-
>>    arch/x86/xen/enlighten_pv.c  |  2 +-
>>    drivers/xen/grant-dma-ops.c  | 10 ++++++++++
>>    include/xen/xen-ops.h        |  1 +
>>    4 files changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
>> index 1c1ac418484b..c1cd28e915a3 100644
>> --- a/arch/x86/xen/enlighten_hvm.c
>> +++ b/arch/x86/xen/enlighten_hvm.c
>> @@ -212,7 +212,7 @@ static void __init xen_hvm_guest_init(void)
>>    		return;
>>    
>>    	if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT))
>> -		virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
>> +		virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
>>    
>>    	init_hvm_pv_info();
>>    
>> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
>> index 9b1a58dda935..45b24c1b646a 100644
>> --- a/arch/x86/xen/enlighten_pv.c
>> +++ b/arch/x86/xen/enlighten_pv.c
>> @@ -112,7 +112,7 @@ static void __init xen_pv_init_platform(void)
>>    {
>>    	/* PV guests can't operate virtio devices without grants. */
>>    	if (IS_ENABLED(CONFIG_XEN_VIRTIO))
>> -		virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
>> +		virtio_set_mem_acc_cb(xen_virtio_restricted_mem_acc);
>>    
>>    	populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));
>>    
>> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
>> index a00112235877..60a7acc334ed 100644
>> --- a/drivers/xen/grant-dma-ops.c
>> +++ b/drivers/xen/grant-dma-ops.c
>> @@ -372,6 +372,16 @@ void xen_grant_setup_dma_ops(struct device *dev)
>>    	dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
>>    }
>>    
>> +bool xen_virtio_restricted_mem_acc(struct virtio_device *dev)
>> +{
>> +	bool ret = xen_virtio_mem_acc(dev);
> 
> 
> The grant usage is mandatory for PV guests, right?
> 
> Then xen_virtio_mem_acc() should always return true for PV guests (I
> mean even if CONFIG_XEN_VIRTIO_FORCE_GRANT is not set).

Yes.

> 
> 
> 
>> +
>> +	if (ret)
>> +		xen_grant_setup_dma_ops(dev->dev.parent);
>> +
>> +	return ret;
>> +}
>> +
>>    MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
>>    MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
>>    MODULE_LICENSE("GPL");
>> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
>> index dae0f350c678..3dd5aa936f1d 100644
>> --- a/include/xen/xen-ops.h
>> +++ b/include/xen/xen-ops.h
>> @@ -219,6 +219,7 @@ static inline void xen_preemptible_hcall_end(void) { }
>>    void xen_grant_setup_dma_ops(struct device *dev);
>>    bool xen_is_grant_dma_device(struct device *dev);
>>    bool xen_virtio_mem_acc(struct virtio_device *dev);
>> +bool xen_virtio_restricted_mem_acc(struct virtio_device *dev);
>>    #else
>>    static inline void xen_grant_setup_dma_ops(struct device *dev)
>>    {
> 
> 
> And probably static inline stub always returning false if
> CONFIG_XEN_GRANT_DMA_OPS is not set.

Indeed.


Juergen


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Re: [PATCH 1/3] xen/virtio: restructure xen grant dma setup

[Juergen Gross]

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On 06.10.22 18:35, Oleksandr Tyshchenko wrote:
> 
> On 06.10.22 10:14, Juergen Gross wrote:
> 
> Hello Juergen
> 
>> In order to prepare supporting other means than device tree for
>> setting up virtio devices under Xen, restructure the functions
>> xen_is_grant_dma_device() and xen_grant_setup_dma_ops() a little bit.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> 
> Patch looks good,
> 
> one NIT, xen_dt_grant_setup_dma_ops() down the code doesn't actually
> setup DMA OPS, it retrieves the backend domid via device-tree means and
> stores it,
> 
> so I would rename to it, maybe something like
> xen_dt_grant_setup_backend_domid() or xen_dt_grant_init_backend_domid(),
> but I am not sure it would be good alternative.

I'll go with xen_dt_grant_init_backend_domid().

> 
> 
> So, w/ or w/o renaming:
> 
> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> also
> 
> Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64
> only

Thanks,


Juergen


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