Re: [Xen-devel] [PATCH v7] x86/mem-sharing: mem-sharing a range of memory

[Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

On Tue, Jul 19, 2016 at 1:54 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
> Hello Tamas,
>
> On 18/07/2016 22:14, Tamas K Lengyel wrote:
>>
>> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
>> index e904bd5..0ca94cd 100644
>> --- a/tools/libxc/include/xenctrl.h
>> +++ b/tools/libxc/include/xenctrl.h
>> @@ -2334,6 +2334,21 @@ int xc_memshr_add_to_physmap(xc_interface *xch,
>>                      domid_t client_domain,
>>                      unsigned long client_gfn);
>>
>> +/* Allows to deduplicate a range of memory of a client domain. Using
>> + * this function is equivalent of calling xc_memshr_nominate_gfn for each
>> gfn
>> + * in the two domains followed by xc_memshr_share_gfns.
>> + *
>> + * May fail with -EINVAL if the source and client domain have different
>> + * memory size or if memory sharing is not enabled on either of the
>> domains.
>> + * May also fail with -ENOMEM if there isn't enough memory available to
>> store
>> + * the sharing metadata before deduplication can happen.
>> + */
>> +int xc_memshr_range_share(xc_interface *xch,
>> +                          domid_t source_domain,
>> +                          domid_t client_domain,
>> +                          unsigned long start,
>> +                          unsigned long end);
>
>
> I know the rest of memshr interface in libxc is using "unsigned long".
> However, this should really be "uint64_t" to match the interface and avoid
> issue with 32-bit toolstack on 64-bit hypervisor.

Sounds good to me.

>
>> +
>>  /* Debug calls: return the number of pages referencing the shared frame
>> backing
>>   * the input argument. Should be one or greater.
>>   *
>
>
> [...]
>
>> diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
>> index a522423..6d00228 100644
>> --- a/xen/arch/x86/mm/mem_sharing.c
>> +++ b/xen/arch/x86/mm/mem_sharing.c
>
>
> [...]
>
>> @@ -1468,6 +1520,94 @@ int
>> mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
>>          }
>>          break;
>>
>> +        case XENMEM_sharing_op_range_share:
>> +        {
>> +            unsigned long max_sgfn, max_cgfn;
>> +            struct domain *cd;
>> +
>> +            rc = -EINVAL;
>> +            if( mso.u.range._pad[0] || mso.u.range._pad[1] ||
>
>
> NIT: missing space after the "if".
>
>> +                mso.u.range._pad[2] )
>> +                goto out;
>> +
>
>
> Regards,
>
> --
> Julien Grall

Thanks!
Tamas

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