Re: [PATCH v8 5/5] Driver: VMBus: Add Devicetree support

Saurabh Singh Sengar
2023-03-15T05:29:52Z

On Tue, Mar 14, 2023 at 09:21:32PM +0000, Michael Kelley (LINUX) wrote:
> From: Saurabh Sengar <ssengar@linux.microsoft.com> Sent: Tuesday, March 14, 2023 2:16 AM
> >
> > Update the driver to support Devicetree boot as well along with ACPI.
> > At present the Devicetree parsing only provides the mmio region info
> > and is not the exact copy of ACPI parsing. This is sufficient to cater
> > all the current Devicetree usecases for VMBus.
> >
> > Currently Devicetree is supported only for x86 systems.
> >
> > Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> > ---
> > [V8]
> > - Remove the auto select of CONFIG_OF
> > - Remove the dependency on !ACPI for OF_EARLY_FLATTREE
> > - Used acpi_disabled instead of #ifdef and hence added a dummy function
> > for vmbus_acpi_add
> > - GFP_ATOMIC -> GFP_KERNEL
> > - used range.flags instead of hard coding flags
> > - used __maybe_unused for acpi device id, removed #ifdef
> >
> > drivers/hv/Kconfig | 5 ++--
> > drivers/hv/vmbus_drv.c | 64 +++++++++++++++++++++++++++++++++++++++---
> > 2 files changed, 63 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> > index 0747a8f1fcee..47132b30b7ee 100644
> > --- a/drivers/hv/Kconfig
> > +++ b/drivers/hv/Kconfig
> > @@ -4,11 +4,12 @@ menu "Microsoft Hyper-V guest support"
> >
> > config HYPERV
> > tristate "Microsoft Hyper-V client drivers"
> > - depends on ACPI && ((X86 && X86_LOCAL_APIC && HYPERVISOR_GUEST) \
> > - || (ARM64 && !CPU_BIG_ENDIAN))
> > + depends on (X86 && X86_LOCAL_APIC && HYPERVISOR_GUEST) \
> > + || (ACPI && ARM64 && !CPU_BIG_ENDIAN)
> > select PARAVIRT
> > select X86_HV_CALLBACK_VECTOR if X86
> > select VMAP_PFN
> > + select OF_EARLY_FLATTREE if OF
> > help
> > Select this option to run Linux as a Hyper-V client operating
> > system.
> > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> > index 3ad2fa2b92e7..15097e1f3f2b 100644
> > --- a/drivers/hv/vmbus_drv.c
> > +++ b/drivers/hv/vmbus_drv.c
> > @@ -20,6 +20,7 @@
> > #include <linux/completion.h>
> > #include <linux/hyperv.h>
> > #include <linux/kernel_stat.h>
> > +#include <linux/of_address.h>
> > #include <linux/clockchips.h>
> > #include <linux/cpu.h>
> > #include <linux/sched/isolation.h>
> > @@ -2143,7 +2144,7 @@ void vmbus_device_unregister(struct hv_device *device_obj)
> > device_unregister(&device_obj->device);
> > }
> >
> > -
> > +#ifdef CONFIG_ACPI
> > /*
> > * VMBUS is an acpi enumerated device. Get the information we
> > * need from DSDT.
> > @@ -2253,6 +2254,7 @@ static acpi_status vmbus_walk_resources(struct acpi_resource
> > *res, void *ctx)
> >
> > return AE_OK;
> > }
> > +#endif
> >
> > static void vmbus_mmio_remove(void)
> > {
> > @@ -2273,7 +2275,7 @@ static void vmbus_mmio_remove(void)
> > }
> > }
> >
> > -static void vmbus_reserve_fb(void)
> > +static void __maybe_unused vmbus_reserve_fb(void)
> > {
> > resource_size_t start = 0, size;
> > struct pci_dev *pdev;
> > @@ -2433,6 +2435,7 @@ void vmbus_free_mmio(resource_size_t start, resource_size_t
> > size)
> > }
> > EXPORT_SYMBOL_GPL(vmbus_free_mmio);
> >
> > +#ifdef CONFIG_ACPI
> > static int vmbus_acpi_add(struct platform_device *pdev)
> > {
> > acpi_status result;
> > @@ -2485,10 +2488,52 @@ static int vmbus_acpi_add(struct platform_device *pdev)
> > vmbus_mmio_remove();
> > return ret_val;
> > }
> > +#else
> > +static int vmbus_acpi_add(struct platform_device *pdev)
> > +{
> > + return 0;
> > +}
> > +#endif
> > +
> > +static int vmbus_device_add(struct platform_device *pdev)
> > +{
> > + struct resource **cur_res = &hyperv_mmio;
> > + struct of_range range;
> > + struct of_range_parser parser;
> > + struct device_node *np = pdev->dev.of_node;
> > + int ret;
> > +
> > + hv_dev = &pdev->dev;
> > +
> > + ret = of_range_parser_init(&parser, np);
> > + if (ret)
> > + return ret;
> > +
> > + for_each_of_range(&parser, &range) {
> > + struct resource *res;
> > +
> > + res = kzalloc(sizeof(*res), GFP_KERNEL);
> > + if (!res)
> > + return -ENOMEM;
>
> I should have looked at this more closely in the previous
> revision. But if this error path is taken, does any cleanup
> need to be done of 'res' entries that were allocated in
> previous iterations of the for_each_of_range() loop? It
> seems like the cleanup and releasing of previously allocated
> memory should be done.

No problem, thanks for pointing this.
For now we have only one range in device tree so this case may not occur,
but for completeness I agree we should add that, in future we might
have multiple ranges supported.

I will add vmbus_mmio_remove() in case of error here, I guess that
should be sufficient.

>
> > +
> > + res->name = "hyperv mmio";
> > + res->flags = range.flags;
> > + res->start = range.cpu_addr;
> > + res->end = range.cpu_addr + range.size;
> > +
> > + *cur_res = res;
> > + cur_res = &res->sibling;
> > + }
> > +
> > + return ret;
> > +}
> >
> > static int vmbus_platform_driver_probe(struct platform_device *pdev)
> > {
> > - return vmbus_acpi_add(pdev);
> > + if (!acpi_disabled)
> > + return vmbus_acpi_add(pdev);
> > + else
> > + return vmbus_device_add(pdev);
>
> Nit: Usually when there's a negated test with if/else, it's best to flip the
> if and else clauses so as to eliminate the negation. It's just slightly less
> semantic load for the human reader to parse through. So:
>
> if (acpi_disabled)
> return vmbus_device_add(pdev);
> else
> return vmbus_acpi_add(pdev);
>
> Everything else looks good to me.

Sure will fix.

Regards,
Saurabh

>
> Michael
>
> > }
> >
> > static int vmbus_platform_driver_remove(struct platform_device *pdev)
> > @@ -2634,7 +2679,17 @@ static int vmbus_bus_resume(struct device *dev)
> > #define vmbus_bus_resume NULL
> > #endif /* CONFIG_PM_SLEEP */
> >
> > -static const struct acpi_device_id vmbus_acpi_device_ids[] = {
> > +static const __maybe_unused struct of_device_id vmbus_of_match[] = {
> > + {
> > + .compatible = "microsoft,vmbus",
> > + },
> > + {
> > + /* sentinel */
> > + },
> > +};
> > +MODULE_DEVICE_TABLE(of, vmbus_of_match);
> > +
> > +static const __maybe_unused struct acpi_device_id vmbus_acpi_device_ids[] = {
> > {"VMBUS", 0},
> > {"VMBus", 0},
> > {"", 0},
> > @@ -2668,6 +2723,7 @@ static struct platform_driver vmbus_platform_driver = {
> > .driver = {
> > .name = "vmbus",
> > .acpi_match_table = ACPI_PTR(vmbus_acpi_device_ids),
> > + .of_match_table = of_match_ptr(vmbus_of_match),
> > .pm = &vmbus_bus_pm,
> > .probe_type = PROBE_FORCE_SYNCHRONOUS,
> > }
> > --
> > 2.34.1