Re: [PATCH v3 10/17] xen/arm: Add cmdline boot option "pci-passthrough = <boolean>"

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Rahul,

> On 28 Sep 2021, at 19:18, Rahul Singh <rahul.singh@xxxxxxx> wrote:
> 
> Add cmdline boot option "pci-passthrough = = <boolean>" to enable or
> disable the PCI passthrough support on ARM.
> 
> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> Change in v3:
> - Remove "define pci_passthrough_enabled (false)"
> - Fixed coding style and minor comment
> Change in v2:
> - Add option in xen-command-line.pandoc
> - Change pci option to pci-passthrough
> - modify option from custom_param to boolean param
> ---
> docs/misc/xen-command-line.pandoc |  7 +++++++
> xen/arch/arm/pci/pci.c            | 14 ++++++++++++++
> xen/common/physdev.c              |  6 ++++++
> xen/include/asm-arm/pci.h         | 11 +++++++++++
> xen/include/asm-x86/pci.h         |  8 ++++++++
> 5 files changed, 46 insertions(+)
> 
> diff --git a/docs/misc/xen-command-line.pandoc 
> b/docs/misc/xen-command-line.pandoc
> index 177e656f12..c8bf96ccf8 100644
> --- a/docs/misc/xen-command-line.pandoc
> +++ b/docs/misc/xen-command-line.pandoc
> @@ -1808,6 +1808,13 @@ All numbers specified must be hexadecimal ones.
> 
> This option can be specified more than once (up to 8 times at present).
> 
> +### pci-passthrough (arm)
> +> `= <boolean>`
> +
> +> Default: `false`
> +
> +Flag to enable or disable support for PCI passthrough
> +
> ### pcid (x86)
>> `= <boolean> | xpti=<bool>`
> 
> diff --git a/xen/arch/arm/pci/pci.c b/xen/arch/arm/pci/pci.c
> index e359bab9ea..84d8f0d634 100644
> --- a/xen/arch/arm/pci/pci.c
> +++ b/xen/arch/arm/pci/pci.c
> @@ -16,6 +16,7 @@
> #include <xen/device_tree.h>
> #include <xen/errno.h>
> #include <xen/init.h>
> +#include <xen/param.h>
> #include <xen/pci.h>
> 
> /*
> @@ -62,8 +63,21 @@ static int __init acpi_pci_init(void)
> }
> #endif
> 
> +/*
> + * By default pci passthrough is disabled
> + */
> +bool __read_mostly pci_passthrough_enabled = false;
> +boolean_param("pci-passthrough", pci_passthrough_enabled);
> +
> static int __init pci_init(void)
> {
> +    /*
> +     * Enable PCI passthrough when has been enabled explicitly
> +     * (pci-passthrough=on)
> +     */
> +    if ( !pci_passthrough_enabled )
> +        return 0;
> +
>     pci_segments_init();
> 
>     if ( acpi_disabled )
> diff --git a/xen/common/physdev.c b/xen/common/physdev.c
> index 20a5530269..2d5fc886fc 100644
> --- a/xen/common/physdev.c
> +++ b/xen/common/physdev.c
> @@ -19,6 +19,9 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
> arg)
>         struct pci_dev_info pdev_info;
>         nodeid_t node;
> 
> +        if ( !is_pci_passthrough_enabled() )
> +            return -ENOSYS;
> +
>         ret = -EFAULT;
>         if ( copy_from_guest(&add, arg, 1) != 0 )
>             break;
> @@ -54,6 +57,9 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
> arg)
>     case PHYSDEVOP_pci_device_remove: {
>         struct physdev_pci_device dev;
> 
> +        if ( !is_pci_passthrough_enabled() )
> +            return -ENOSYS;
> +
>         ret = -EFAULT;
>         if ( copy_from_guest(&dev, arg, 1) != 0 )
>             break;
> diff --git a/xen/include/asm-arm/pci.h b/xen/include/asm-arm/pci.h
> index 7dd9eb3dba..0cf849e26f 100644
> --- a/xen/include/asm-arm/pci.h
> +++ b/xen/include/asm-arm/pci.h
> @@ -19,14 +19,25 @@
> 
> #define pci_to_dev(pcidev) (&(pcidev)->arch.dev)
> 
> +extern bool_t pci_passthrough_enabled;
> +
> /* Arch pci dev struct */
> struct arch_pci_dev {
>     struct device dev;
> };
> 
> +static always_inline bool is_pci_passthrough_enabled(void)
> +{
> +    return pci_passthrough_enabled;
> +}
> #else   /*!CONFIG_HAS_PCI*/
> 
> struct arch_pci_dev { };
> 
> +static always_inline bool is_pci_passthrough_enabled(void)
> +{
> +    return false;
> +}
> +
> #endif  /*!CONFIG_HAS_PCI*/
> #endif /* __ARM_PCI_H__ */
> diff --git a/xen/include/asm-x86/pci.h b/xen/include/asm-x86/pci.h
> index cc05045e9c..3f806ce7a8 100644
> --- a/xen/include/asm-x86/pci.h
> +++ b/xen/include/asm-x86/pci.h
> @@ -32,4 +32,12 @@ bool_t pci_ro_mmcfg_decode(unsigned long mfn, unsigned int 
> *seg,
> extern int pci_mmcfg_config_num;
> extern struct acpi_mcfg_allocation *pci_mmcfg_config;
> 
> +/*
> + * Unlike ARM, PCI passthrough is always enabled for x86.
> + */
> +static always_inline bool is_pci_passthrough_enabled(void)
> +{
> +    return true;
> +}
> +
> #endif /* __X86_PCI_H__ */
> -- 
> 2.17.1
>