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

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

On 23.09.21 23:00, Stefano Stabellini wrote:
> On Thu, 23 Sep 2021, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
>>
>> 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@xxxxxxxx>
>> Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@xxxxxxxx>
> 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