Re: [PATCH v3 2/2] xen-pciback: allow compiling on other archs than x86

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>]

On 23.09.21 23:00, Stefano Stabellini wrote:
> On Thu, 23 Sep 2021, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> Xen-pciback driver was designed to be built for x86 only. But it
>> can also be used by other architectures, e.g. Arm.
>> Re-structure the driver in a way that it can be built for other
>> platforms as well.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>
> The patch looks good to me. Only one thing: on ARM32 I get:
WE do not yet support Xen PCI passthrough for ARM32
>
> drivers/xen/xen-pciback/conf_space_header.c: In function ‘bar_init’:
> drivers/xen/xen-pciback/conf_space_header.c:239:34: warning: right shift count >= width of type [-Wshift-count-overflow]
>      bar->val = res[pos - 1].start >> 32;
>                                    ^~
> drivers/xen/xen-pciback/conf_space_header.c:240:49: warning: right shift count >= width of type [-Wshift-count-overflow]
>      bar->len_val = -resource_size(&res[pos - 1]) >> 32;
>   
>   
> resource_size_t is defined as phys_addr_t and it can be 32bit on arm32.
>
>
> One fix is to surround:
>
> 		if (pos && (res[pos - 1].flags & IORESOURCE_MEM_64)) {
> 			bar->val = res[pos - 1].start >> 32;
> 			bar->len_val = -resource_size(&res[pos - 1]) >> 32;
> 			return bar;
> 		}
>
> with #ifdef PHYS_ADDR_T_64BIT
>
This might not be correct. We are dealing here with a 64-bit BAR on a 32-bit OS.

I think that this can still be valid use-case if BAR64.hi == 0. So, not sure

we can just skip it with ifdef.

Instead, to be on the safe side, we can have:

config XEN_PCIDEV_STUB
        tristate "Xen PCI-device stub driver"
        depends on PCI && ARM64 && XEN
e.g. only allow building the "stub" for ARM64 for now.


>
>> ---
>> Since v2:
>>   - swap the patch order
>> Since v1:
>>   - Do not move pci_xen_initial_domain as it is x86 specific
>> ---
>>   arch/x86/include/asm/xen/pci.h     | 18 +------
>>   arch/x86/pci/xen.c                 | 74 +----------------------------
>>   drivers/xen/pci.c                  | 75 ++++++++++++++++++++++++++++++
>>   drivers/xen/xen-pciback/pci_stub.c |  3 +-
>>   drivers/xen/xen-pciback/xenbus.c   |  2 +-
>>   include/xen/pci.h                  | 28 +++++++++++
>>   6 files changed, 108 insertions(+), 92 deletions(-)
>>   create mode 100644 include/xen/pci.h
>>
>> diff --git a/arch/x86/include/asm/xen/pci.h b/arch/x86/include/asm/xen/pci.h
>> index 3506d8c598c1..2889f091f459 100644
>> --- a/arch/x86/include/asm/xen/pci.h
>> +++ b/arch/x86/include/asm/xen/pci.h
>> @@ -16,26 +16,10 @@ static inline int pci_xen_hvm_init(void)
>>   #endif
>>   #if defined(CONFIG_XEN_DOM0)
>>   int __init pci_xen_initial_domain(void);
>> -int xen_find_device_domain_owner(struct pci_dev *dev);
>> -int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain);
>> -int xen_unregister_device_domain_owner(struct pci_dev *dev);
>>   #else
>>   static inline int __init pci_xen_initial_domain(void)
>>   {
>> -	return -1;
>> -}
>> -static inline int xen_find_device_domain_owner(struct pci_dev *dev)
>> -{
>> -	return -1;
>> -}
>> -static inline int xen_register_device_domain_owner(struct pci_dev *dev,
>> -						   uint16_t domain)
>> -{
>> -	return -1;
>> -}
>> -static inline int xen_unregister_device_domain_owner(struct pci_dev *dev)
>> -{
>> -	return -1;
>> +       return -1;
>>   }
>>   #endif
>>   
>> diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
>> index 3d41a09c2c14..4a45b0bf9ae4 100644
>> --- a/arch/x86/pci/xen.c
>> +++ b/arch/x86/pci/xen.c
>> @@ -23,6 +23,7 @@
>>   
>>   #include <xen/features.h>
>>   #include <xen/events.h>
>> +#include <xen/pci.h>
>>   #include <asm/xen/pci.h>
>>   #include <asm/xen/cpuid.h>
>>   #include <asm/apic.h>
>> @@ -583,77 +584,4 @@ int __init pci_xen_initial_domain(void)
>>   	}
>>   	return 0;
>>   }
>> -
>> -struct xen_device_domain_owner {
>> -	domid_t domain;
>> -	struct pci_dev *dev;
>> -	struct list_head list;
>> -};
>> -
>> -static DEFINE_SPINLOCK(dev_domain_list_spinlock);
>> -static struct list_head dev_domain_list = LIST_HEAD_INIT(dev_domain_list);
>> -
>> -static struct xen_device_domain_owner *find_device(struct pci_dev *dev)
>> -{
>> -	struct xen_device_domain_owner *owner;
>> -
>> -	list_for_each_entry(owner, &dev_domain_list, list) {
>> -		if (owner->dev == dev)
>> -			return owner;
>> -	}
>> -	return NULL;
>> -}
>> -
>> -int xen_find_device_domain_owner(struct pci_dev *dev)
>> -{
>> -	struct xen_device_domain_owner *owner;
>> -	int domain = -ENODEV;
>> -
>> -	spin_lock(&dev_domain_list_spinlock);
>> -	owner = find_device(dev);
>> -	if (owner)
>> -		domain = owner->domain;
>> -	spin_unlock(&dev_domain_list_spinlock);
>> -	return domain;
>> -}
>> -EXPORT_SYMBOL_GPL(xen_find_device_domain_owner);
>> -
>> -int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain)
>> -{
>> -	struct xen_device_domain_owner *owner;
>> -
>> -	owner = kzalloc(sizeof(struct xen_device_domain_owner), GFP_KERNEL);
>> -	if (!owner)
>> -		return -ENODEV;
>> -
>> -	spin_lock(&dev_domain_list_spinlock);
>> -	if (find_device(dev)) {
>> -		spin_unlock(&dev_domain_list_spinlock);
>> -		kfree(owner);
>> -		return -EEXIST;
>> -	}
>> -	owner->domain = domain;
>> -	owner->dev = dev;
>> -	list_add_tail(&owner->list, &dev_domain_list);
>> -	spin_unlock(&dev_domain_list_spinlock);
>> -	return 0;
>> -}
>> -EXPORT_SYMBOL_GPL(xen_register_device_domain_owner);
>> -
>> -int xen_unregister_device_domain_owner(struct pci_dev *dev)
>> -{
>> -	struct xen_device_domain_owner *owner;
>> -
>> -	spin_lock(&dev_domain_list_spinlock);
>> -	owner = find_device(dev);
>> -	if (!owner) {
>> -		spin_unlock(&dev_domain_list_spinlock);
>> -		return -ENODEV;
>> -	}
>> -	list_del(&owner->list);
>> -	spin_unlock(&dev_domain_list_spinlock);
>> -	kfree(owner);
>> -	return 0;
>> -}
>> -EXPORT_SYMBOL_GPL(xen_unregister_device_domain_owner);
>>   #endif
>> diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
>> index 224df03ce42e..fc8c1249d49f 100644
>> --- a/drivers/xen/pci.c
>> +++ b/drivers/xen/pci.c
>> @@ -254,3 +254,78 @@ static int xen_mcfg_late(void)
>>   	return 0;
>>   }
>>   #endif
>> +
>> +#ifdef CONFIG_XEN_DOM0
>> +struct xen_device_domain_owner {
>> +	domid_t domain;
>> +	struct pci_dev *dev;
>> +	struct list_head list;
>> +};
>> +
>> +static DEFINE_SPINLOCK(dev_domain_list_spinlock);
>> +static struct list_head dev_domain_list = LIST_HEAD_INIT(dev_domain_list);
>> +
>> +static struct xen_device_domain_owner *find_device(struct pci_dev *dev)
>> +{
>> +	struct xen_device_domain_owner *owner;
>> +
>> +	list_for_each_entry(owner, &dev_domain_list, list) {
>> +		if (owner->dev == dev)
>> +			return owner;
>> +	}
>> +	return NULL;
>> +}
>> +
>> +int xen_find_device_domain_owner(struct pci_dev *dev)
>> +{
>> +	struct xen_device_domain_owner *owner;
>> +	int domain = -ENODEV;
>> +
>> +	spin_lock(&dev_domain_list_spinlock);
>> +	owner = find_device(dev);
>> +	if (owner)
>> +		domain = owner->domain;
>> +	spin_unlock(&dev_domain_list_spinlock);
>> +	return domain;
>> +}
>> +EXPORT_SYMBOL_GPL(xen_find_device_domain_owner);
>> +
>> +int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain)
>> +{
>> +	struct xen_device_domain_owner *owner;
>> +
>> +	owner = kzalloc(sizeof(struct xen_device_domain_owner), GFP_KERNEL);
>> +	if (!owner)
>> +		return -ENODEV;
>> +
>> +	spin_lock(&dev_domain_list_spinlock);
>> +	if (find_device(dev)) {
>> +		spin_unlock(&dev_domain_list_spinlock);
>> +		kfree(owner);
>> +		return -EEXIST;
>> +	}
>> +	owner->domain = domain;
>> +	owner->dev = dev;
>> +	list_add_tail(&owner->list, &dev_domain_list);
>> +	spin_unlock(&dev_domain_list_spinlock);
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(xen_register_device_domain_owner);
>> +
>> +int xen_unregister_device_domain_owner(struct pci_dev *dev)
>> +{
>> +	struct xen_device_domain_owner *owner;
>> +
>> +	spin_lock(&dev_domain_list_spinlock);
>> +	owner = find_device(dev);
>> +	if (!owner) {
>> +		spin_unlock(&dev_domain_list_spinlock);
>> +		return -ENODEV;
>> +	}
>> +	list_del(&owner->list);
>> +	spin_unlock(&dev_domain_list_spinlock);
>> +	kfree(owner);
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(xen_unregister_device_domain_owner);
>> +#endif
>> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
>> index f8e4faa96ad6..bba527620507 100644
>> --- a/drivers/xen/xen-pciback/pci_stub.c
>> +++ b/drivers/xen/xen-pciback/pci_stub.c
>> @@ -19,7 +19,8 @@
>>   #include <linux/sched.h>
>>   #include <linux/atomic.h>
>>   #include <xen/events.h>
>> -#include <asm/xen/pci.h>
>> +#include <xen/pci.h>
>> +#include <xen/xen.h>
>>   #include <asm/xen/hypervisor.h>
>>   #include <xen/interface/physdev.h>
>>   #include "pciback.h"
>> diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
>> index f8ba2903a3ff..bde63ef677b8 100644
>> --- a/drivers/xen/xen-pciback/xenbus.c
>> +++ b/drivers/xen/xen-pciback/xenbus.c
>> @@ -14,7 +14,7 @@
>>   #include <linux/workqueue.h>
>>   #include <xen/xenbus.h>
>>   #include <xen/events.h>
>> -#include <asm/xen/pci.h>
>> +#include <xen/pci.h>
>>   #include "pciback.h"
>>   
>>   #define INVALID_EVTCHN_IRQ  (-1)
>> diff --git a/include/xen/pci.h b/include/xen/pci.h
>> new file mode 100644
>> index 000000000000..b8337cf85fd1
>> --- /dev/null
>> +++ b/include/xen/pci.h
>> @@ -0,0 +1,28 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +
>> +#ifndef __XEN_PCI_H__
>> +#define __XEN_PCI_H__
>> +
>> +#if defined(CONFIG_XEN_DOM0)
>> +int xen_find_device_domain_owner(struct pci_dev *dev);
>> +int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain);
>> +int xen_unregister_device_domain_owner(struct pci_dev *dev);
>> +#else
>> +static inline int xen_find_device_domain_owner(struct pci_dev *dev)
>> +{
>> +	return -1;
>> +}
>> +
>> +static inline int xen_register_device_domain_owner(struct pci_dev *dev,
>> +						   uint16_t domain)
>> +{
>> +	return -1;
>> +}
>> +
>> +static inline int xen_unregister_device_domain_owner(struct pci_dev *dev)
>> +{
>> +	return -1;
>> +}
>> +#endif
>> +
>> +#endif
>> -- 
>> 2.25.1