Re: [v4][PATCH 2/9] xen:x86: define a new hypercall to get RMRR mappings

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/8/22 18:53, Andrew Cooper wrote:
> On 22/08/14 11:09, Tiejun Chen wrote:
>> We need this new hypercall to get RMRR mapping for VM.
>>
>> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
>> ---
>>   xen/arch/x86/mm.c           | 71 +++++++++++++++++++++++++++++++++++++++++++++
>>   xen/include/public/memory.h | 37 ++++++++++++++++++++++-
>>   2 files changed, 107 insertions(+), 1 deletion(-)
>>
>> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
>> index d23cb3f..e0d6650 100644
>> --- a/xen/arch/x86/mm.c
>> +++ b/xen/arch/x86/mm.c
>> @@ -123,6 +123,7 @@
>>   #include <asm/setup.h>
>>   #include <asm/fixmap.h>
>>   #include <asm/pci.h>
>> +#include <asm/acpi.h>
>>
>>   /* Mapping of the fixmap space needed early. */
>>   l1_pgentry_t __attribute__ ((__section__ (".bss.page_aligned")))
>> @@ -4842,6 +4843,76 @@ long arch_memory_op(unsigned long cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>           return rc;
>>       }
>>
>> +    case XENMEM_reserved_device_memory_map:
>> +    {
>> +        struct xen_reserved_device_memory_map map;
>> +        XEN_GUEST_HANDLE(xen_reserved_device_memory_t) buffer;
>> +        XEN_GUEST_HANDLE_PARAM(xen_reserved_device_memory_t) buffer_param;
>> +        unsigned int i = 0;
>> +        static unsigned int nr_entries = 0;
>> +        static struct xen_reserved_device_memory *rmrr_map;
>
> Absolutely not.  This hypercall can easy be run concurrently.
>
>> +        struct acpi_rmrr_unit *rmrr;
>> +
>> +        if ( copy_from_guest(&map, arg, 1) )
>> +            return -EFAULT;
>> +
>> +        if ( !nr_entries )
>> +            /* Currently we just need to cover RMRR. */
>> +            list_for_each_entry( rmrr, &acpi_rmrr_units, list )
>> +                nr_entries++;
>
> Maintain a global count as entries are added/removed from this list.  It
> is a waste of time recounting this list for each hypercall.

Are you saying push this 'nr_entries' as a global count somewhere? I 
guess I can set this when we first construct acpi_rmrr_units in ACPI stuff.

>
>> +
>> +        if ( !nr_entries )
>> +                return -ENOENT;
>> +        else
>> +        {
>> +            if ( rmrr_map == NULL )
>> +            {
>> +                rmrr_map = xmalloc_array(xen_reserved_device_memory_t,
>> +                                         nr_entries);
>
> You can do all of this without any memory allocation.

I will check this.

>
>> +                if ( rmrr_map == NULL )
>> +                {
>> +                    return -ENOMEM;
>> +                }
>> +
>> +                list_for_each_entry( rmrr, &acpi_rmrr_units, list )
>> +                {
>> +                    rmrr_map[i].pfn = rmrr->base_address >> PAGE_SHIFT;
>> +                    rmrr_map[i].count = PAGE_ALIGN(rmrr->end_address -
>> +                                                   rmrr->base_address) /
>> +                                                   PAGE_SIZE;
>> +                    i++;
>> +                }
>> +            }
>> +        }
>> +
>> +        if ( map.nr_entries < nr_entries )
>> +        {
>> +            map.nr_entries =  nr_entries;
>> +            if ( copy_to_guest(arg, &map, 1) )
>> +                return -EFAULT;
>> +            return -ENOBUFS;
>> +        }
>> +
>> +        map.nr_entries =  nr_entries;
>> +        buffer_param = guest_handle_cast(map.buffer,
>> +                                         xen_reserved_device_memory_t);
>> +        buffer = guest_handle_from_param(buffer_param,
>> +                                         xen_reserved_device_memory_t);
>> +        if ( !guest_handle_okay(buffer, map.nr_entries) )
>> +            return -EFAULT;
>> +
>> +        for ( i = 0; i < map.nr_entries; ++i )
>> +        {
>> +            if ( copy_to_guest_offset(buffer, i, rmrr_map + i, 1) )
>> +                return -EFAULT;
>> +        }
>> +
>> +        if ( copy_to_guest(arg, &map, 1) )
>> +                return -EFAULT;
>> +
>> +        return 0;
>> +    }
>> +
>>       default:
>>           return subarch_memory_op(cmd, arg);
>>       }
>> diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
>> index 2c57aa0..8481843 100644
>> --- a/xen/include/public/memory.h
>> +++ b/xen/include/public/memory.h
>> @@ -523,7 +523,42 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_sharing_op_t);
>>
>>   #endif /* defined(__XEN__) || defined(__XEN_TOOLS__) */
>>
>> -/* Next available subop number is 26 */
>> +/*
>> + * Some devices may reserve some range.
>
> "range" is not a useful unit of measure.

So what about this?

The regions of memory used for some devices should be reserved.

>
>> + *
>> + * Currently we just have RMRR
>> + * - Reserved memory Region Reporting Structure,
>> + * So returns the RMRR memory map as it was when the domain
>> + * was started.
>> + */
>> +#define XENMEM_reserved_device_memory_map   26
>> +struct xen_reserved_device_memory {
>
> xen_mem_ to match the prevailing style

Okay.

>
>> +    /* PFN of the current mapping of the page. */
>> +    xen_pfn_t pfn;
>> +    /* Number of the current mapping pages. */
>> +    xen_ulong_t count;
>> +};
>
> This struct marks a range, but the fields don't make it clear.  I would
> suggest "start" and "nr_frames" as names.
>

I will prefer Jan's suggestion.

Thanks
Tiejun

> ~Andrew
>
>> +typedef struct xen_reserved_device_memory xen_reserved_device_memory_t;
>> +DEFINE_XEN_GUEST_HANDLE(xen_reserved_device_memory_t);
>> +
>> +struct xen_reserved_device_memory_map {
>> +    /*
>> +     * On call the number of entries which can be stored in buffer. On
>> +     * return the number of entries which have been stored in
>> +     * buffer.
>> +     */
>> +    unsigned int nr_entries;
>> +
>> +    /*
>> +     * Entries in the buffer are in the same format as
>> +     * xen_reserved_device_memory.
>> +     */
>> +    XEN_GUEST_HANDLE(void) buffer;
>> +};
>> +typedef struct xen_reserved_device_memory_map xen_reserved_device_memory_map_t;
>> +DEFINE_XEN_GUEST_HANDLE(xen_reserved_device_memory_map_t);
>> +
>> +/* Next available subop number is 27 */
>>
>>   #endif /* __XEN_PUBLIC_MEMORY_H__ */
>>
>
>