Re: [PATCH v5 2/2] xen/pci: replace call to is_memory_hole to pci_check_bar

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 8 Sep 2022, Rahul Singh wrote:
> is_memory_hole was implemented for x86 and not for ARM when introduced.
> Replace is_memory_hole call to pci_check_bar as function should check
> if device BAR is in defined memory range. Also, add an implementation
> for ARM which is required for PCI passthrough.
> 
> On x86, pci_check_bar will call is_memory_hole which will check if BAR
> is not overlapping with any memory region defined in the memory map.
> 
> On ARM, pci_check_bar will go through the host bridge ranges and check
> if the BAR is in the range of defined ranges.
> 
> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx> # x86, common
> ---
> Changes in v5:
>  - drop use of PFN_UP and PF_DOWN in case addresses are not aligned.
>  - As we drop the PFN_UP and PFN_DOWN we need to use the mfn_to_maddr()
>    to get the BAR address without page shift.
>  - Add TODO comment for address alignment check for ranges.
>  - Added Jan Acked-by for x86 and common code.
> Changes in v4:
>  - check "s <= e" before callback
>  - Add TODO comment for revisiting the function pci_check_bar() when
>    ACPI PCI passthrough support is added.
>  - Not Added the Jan Acked-by as patch is modified.
> Changes in v3:
>  - fix minor comments
> ---
>  xen/arch/arm/include/asm/pci.h     |  2 ++
>  xen/arch/arm/pci/pci-host-common.c | 54 ++++++++++++++++++++++++++++++
>  xen/arch/x86/include/asm/pci.h     | 10 ++++++
>  xen/drivers/passthrough/pci.c      |  8 ++---
>  4 files changed, 70 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/arm/include/asm/pci.h b/xen/arch/arm/include/asm/pci.h
> index 80a2431804..8cb46f6b71 100644
> --- a/xen/arch/arm/include/asm/pci.h
> +++ b/xen/arch/arm/include/asm/pci.h
> @@ -126,6 +126,8 @@ int pci_host_iterate_bridges_and_count(struct domain *d,
>  
>  int pci_host_bridge_mappings(struct domain *d);
>  
> +bool pci_check_bar(const struct pci_dev *pdev, mfn_t start, mfn_t end);
> +
>  #else   /*!CONFIG_HAS_PCI*/
>  
>  struct arch_pci_dev { };
> diff --git a/xen/arch/arm/pci/pci-host-common.c 
> b/xen/arch/arm/pci/pci-host-common.c
> index 89ef30028e..d51cfdf352 100644
> --- a/xen/arch/arm/pci/pci-host-common.c
> +++ b/xen/arch/arm/pci/pci-host-common.c
> @@ -24,6 +24,16 @@
>  
>  #include <asm/setup.h>
>  
> +/*
> + * struct to hold pci device bar.
> + */
> +struct pdev_bar_check
> +{
> +    unsigned long start;
> +    unsigned long end;
> +    bool is_valid;
> +};
> +
>  /*
>   * List for all the pci host bridges.
>   */
> @@ -363,6 +373,50 @@ int __init pci_host_bridge_mappings(struct domain *d)
>      return 0;
>  }
>  
> +/*
> + * TODO: BAR addresses and Root Complex window addresses are not guaranteed
> + * to be page aligned. We should check for alignment but this is not the
> + * right place for alignment check.
> + */
> +static int is_bar_valid(const struct dt_device_node *dev,
> +                        uint64_t addr, uint64_t len, void *data)
> +{
> +    struct pdev_bar_check *bar_data = data;
> +    unsigned long s = bar_data->start;
> +    unsigned long e = bar_data->end;
> +
> +    if ( (s >= addr) && (e <= (addr + len - 1)) )
> +        bar_data->is_valid =  true;

"s" and "e" are "unsigned long" while "addr" and "len" are uint64_t. Is
that OK?

Specifically, considering a potential arm32 case, shouldn't "s" and "e"
be uint64_t as well? Which means pdev_bar_check.start and end should be
uint64_t?


> +    return 0;
> +}
> +
> +/* TODO: Revisit this function when ACPI PCI passthrough support is added. */
> +bool pci_check_bar(const struct pci_dev *pdev, mfn_t start, mfn_t end)
> +{
> +    int ret;
> +    const struct dt_device_node *dt_node;
> +    unsigned long s = mfn_to_maddr(start);
> +    unsigned long e = mfn_to_maddr(end);
> +    struct pdev_bar_check bar_data =  {
> +        .start = s,
> +        .end = e,
> +        .is_valid = false
> +    };
> +
> +    if ( s >= e )
> +        return false;
> +
> +    dt_node = pci_find_host_bridge_node(pdev);
> +    if ( !dt_node )
> +        return false;
> +
> +    ret = dt_for_each_range(dt_node, &is_bar_valid, &bar_data);
> +    if ( ret < 0 )
> +        return false;
> +
> +    return bar_data.is_valid;
> +}
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/xen/arch/x86/include/asm/pci.h b/xen/arch/x86/include/asm/pci.h
> index c8e1a9ecdb..f4a58c8acf 100644
> --- a/xen/arch/x86/include/asm/pci.h
> +++ b/xen/arch/x86/include/asm/pci.h
> @@ -57,4 +57,14 @@ static always_inline bool is_pci_passthrough_enabled(void)
>  
>  void arch_pci_init_pdev(struct pci_dev *pdev);
>  
> +static inline bool pci_check_bar(const struct pci_dev *pdev,
> +                                 mfn_t start, mfn_t end)
> +{
> +    /*
> +     * Check if BAR is not overlapping with any memory region defined
> +     * in the memory map.
> +     */
> +    return is_memory_hole(start, end);
> +}
> +
>  #endif /* __X86_PCI_H__ */
> diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
> index cdaf5c247f..149f68bb6e 100644
> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -304,8 +304,8 @@ static void check_pdev(const struct pci_dev *pdev)
>          if ( rc < 0 )
>              /* Unable to size, better leave memory decoding disabled. */
>              return;
> -        if ( size && !is_memory_hole(maddr_to_mfn(addr),
> -                                     maddr_to_mfn(addr + size - 1)) )
> +        if ( size && !pci_check_bar(pdev, maddr_to_mfn(addr),
> +                                    maddr_to_mfn(addr + size - 1)) )
>          {
>              /*
>               * Return without enabling memory decoding if BAR position is not
> @@ -331,8 +331,8 @@ static void check_pdev(const struct pci_dev *pdev)
>  
>          if ( rc < 0 )
>              return;
> -        if ( size && !is_memory_hole(maddr_to_mfn(addr),
> -                                     maddr_to_mfn(addr + size - 1)) )
> +        if ( size && !pci_check_bar(pdev, maddr_to_mfn(addr),
> +                                    maddr_to_mfn(addr + size - 1)) )
>          {
>              printk(warn, &pdev->sbdf, "ROM ", PFN_DOWN(addr),
>                     PFN_DOWN(addr + size - 1));
> -- 
> 2.25.1
>