Re: [PATCH v10 06/17] Xen: ARM: Add support for mapping platform device mmio

[Julien Grall <julien.grall@arm.com>]

Hi Shannon,

Sorry to come late in the review process.

On 01/04/2016 16:49, Shannon Zhao wrote:
> Add a bus_notifier for platform bus device in order to map the device
> mmio regions when DOM0 booting with ACPI.
>
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> ---
>   drivers/xen/Makefile     |   1 +
>   drivers/xen/arm-device.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 142 insertions(+)
>   create mode 100644 drivers/xen/arm-device.c
>
> diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
> index 9b7a35c..415f286 100644
> --- a/drivers/xen/Makefile
> +++ b/drivers/xen/Makefile
> @@ -9,6 +9,7 @@ CFLAGS_features.o			:= $(nostackp)
>
>   CFLAGS_efi.o				+= -fshort-wchar
>
> +dom0-$(CONFIG_ARM64) += arm-device.o
>   dom0-$(CONFIG_PCI) += pci.o
>   dom0-$(CONFIG_USB_SUPPORT) += dbgp.o
>   dom0-$(CONFIG_XEN_ACPI) += acpi.o $(xen-pad-y)
> diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
> new file mode 100644
> index 0000000..76e26e5
> --- /dev/null
> +++ b/drivers/xen/arm-device.c
> @@ -0,0 +1,141 @@
> +/*
> + * Copyright (c) 2015, Linaro Limited, Shannon Zhao
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/platform_device.h>
> +#include <linux/acpi.h>
> +#include <xen/xen.h>
> +#include <xen/page.h>
> +#include <xen/interface/memory.h>
> +#include <asm/xen/hypervisor.h>
> +#include <asm/xen/hypercall.h>
> +
> +static int xen_unmap_device_mmio(struct resource *resource, unsigned int count)

NITs:

There is multiple resource so s/resource/resources/.

Also the variable could be const.

> +{
> +	unsigned int i, j, nr;
> +	int rc = 0;
> +	struct resource *r;
> +	struct xen_remove_from_physmap xrp;
> +
> +	for (i = 0; i < count; i++) {
> +		r = &resource[i];
> +		nr = DIV_ROUND_UP(resource_size(r), XEN_PAGE_SIZE);
> +		if ((resource_type(r) != IORESOURCE_MEM) || (nr == 0))
> +			continue;
> +
> +		for (j = 0; j < nr; j++) {
> +			xrp.domid = DOMID_SELF;
> +			xrp.gpfn = XEN_PFN_DOWN(r->start) + j;
> +			rc = HYPERVISOR_memory_op(XENMEM_remove_from_physmap,
> +						  &xrp);
> +			if (rc)
> +				return rc;
> +		}
> +	}
> +
> +	return rc;
> +}
> +
> +static int xen_map_device_mmio(struct resource *resource, unsigned int count)

Ditto

> +{
> +	unsigned int i, j, nr;
> +	int rc = 0;
> +	struct resource *r;
> +	xen_pfn_t *gpfns;
> +	xen_ulong_t *idxs;
> +	int *errs;
> +	struct xen_add_to_physmap_range xatp;
> +
> +	for (i = 0; i < count; i++) {
> +		r = &resource[i];
> +		nr = DIV_ROUND_UP(resource_size(r), XEN_PAGE_SIZE);
> +		if ((resource_type(r) != IORESOURCE_MEM) || (nr == 0))
> +			continue;
> +
> +		gpfns = kzalloc(sizeof(xen_pfn_t) * nr, GFP_KERNEL);
> +		idxs = kzalloc(sizeof(xen_ulong_t) * nr, GFP_KERNEL);
> +		errs = kzalloc(sizeof(int) * nr, GFP_KERNEL);
> +		if (!gpfns || !idxs || !errs) {
> +			kfree(gpfns);
> +			kfree(idxs);
> +			kfree(errs);
> +			return -ENOMEM;
> +		}
> +
> +		for (j = 0; j < nr; j++) {

I would add a comment to explain that the regions are always mapped 1:1 
to DOM0, and this is fine because the memory map for DOM0 is the same as 
the host (except for the RAM).

> +			gpfns[j] = XEN_PFN_DOWN(r->start) + j;
> +			idxs[j] = XEN_PFN_DOWN(r->start) + j;
> +		}
> +
> +		xatp.domid = DOMID_SELF;
> +		xatp.size = nr;
> +		xatp.space = XENMAPSPACE_dev_mmio;
> +
> +		set_xen_guest_handle(xatp.gpfns, gpfns);
> +		set_xen_guest_handle(xatp.idxs, idxs);
> +		set_xen_guest_handle(xatp.errs, errs);
> +
> +		rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap_range, &xatp);
> +		kfree(gpfns);
> +		kfree(idxs);
> +		kfree(errs);
> +		if (rc)
> +			return rc;

Shouldn't we redo the mapping if the hypercall fails?

> +	}
> +
> +	return rc;
> +}
> +
> +static int xen_platform_notifier(struct notifier_block *nb,
> +				 unsigned long action, void *data)
> +{
> +	struct platform_device *pdev = to_platform_device(data);
> +	int r = 0;
> +
> +	if (pdev->num_resources == 0 || pdev->resource == NULL)
> +		return NOTIFY_OK;
> +
> +	switch (action) {
> +	case BUS_NOTIFY_ADD_DEVICE:
> +		r = xen_map_device_mmio(pdev->resource, pdev->num_resources);
> +		break;
> +	case BUS_NOTIFY_DEL_DEVICE:
> +		r = xen_unmap_device_mmio(pdev->resource, pdev->num_resources);
> +		break;
> +	default:
> +		return NOTIFY_DONE;
> +	}
> +	if (r)
> +		dev_err(&pdev->dev, "Platform: Failed to %s device %s MMIO!\n",
> +			action == BUS_NOTIFY_ADD_DEVICE ? "map" :
> +			(action == BUS_NOTIFY_DEL_DEVICE ? "unmap" : "?"),
> +			pdev->name);
> +
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block platform_device_nb = {
> +	.notifier_call = xen_platform_notifier,
> +};
> +
> +static int __init register_xen_platform_notifier(void)
> +{
> +	if (!xen_initial_domain() || acpi_disabled)
> +		return 0;
> +
> +	return bus_register_notifier(&platform_bus_type, &platform_device_nb);
> +}
> +
> +arch_initcall(register_xen_platform_notifier);
>

Regards,

-- 
Julien Grall