Re: [RFC PATCH] iommu/xen: Add Xen PV-IOMMU driver

[Teddy Astie <teddy.astie@xxxxxxxxxx>]

Le 13/06/2024 à 16:32, Jan Beulich a écrit :
> On 13.06.2024 15:50, Teddy Astie wrote:
>> @@ -214,6 +215,38 @@ struct xen_add_to_physmap_range {
>>   };
>>   DEFINE_GUEST_HANDLE_STRUCT(xen_add_to_physmap_range);
>>
>> +/*
>> + * With some legacy devices, certain guest-physical addresses cannot safely
>> + * be used for other purposes, e.g. to map guest RAM.  This hypercall
>> + * enumerates those regions so the toolstack can avoid using them.
>> + */
>> +#define XENMEM_reserved_device_memory_map   27
>> +struct xen_reserved_device_memory {
>> +    xen_pfn_t start_pfn;
>> +    xen_ulong_t nr_pages;
>> +};
>> +DEFINE_GUEST_HANDLE_STRUCT(xen_reserved_device_memory);
>> +
>> +struct xen_reserved_device_memory_map {
>> +#define XENMEM_RDM_ALL 1 /* Request all regions (ignore dev union). */
>> +    /* IN */
>> +    uint32_t flags;
>> +    /*
>> +     * IN/OUT
>> +     *
>> +     * Gets set to the required number of entries when too low,
>> +     * signaled by error code -ERANGE.
>> +     */
>> +    unsigned int nr_entries;
>> +    /* OUT */
>> +    GUEST_HANDLE(xen_reserved_device_memory) buffer;
>> +    /* IN */
>> +    union {
>> +        struct physdev_pci_device pci;
>> +    } dev;
>> +};
>> +DEFINE_GUEST_HANDLE_STRUCT(xen_reserved_device_memory_map);
>
> This is a tools-only (i.e. unstable) sub-function in Xen; even the comment
> at the top says "toolstack". It is therefore not suitable for use in a
> kernel.
>
IMO this comment actually describes how the toolstack uses the
hypercall, but I don't think it is actually reserved for toolstack use.
Or maybe we should allow the kernel to use this hypercall as well.

>> +
>> +/*
>> + * Local variables:
>> + * mode: C
>> + * c-file-style: "BSD"
>> + * c-basic-offset: 4
>> + * tab-width: 4
>> + * indent-tabs-mode: nil
>> + * End:
>> + */
>> \ No newline at end of file
>
> Nit: I'm pretty sure you want to avoid this.
>
Indeed.

Teddy


Teddy Astie | Vates XCP-ng Intern

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