Re: [Xen-devel] [PATCH RFC] tools/libxc, xen/x86: Added xc_set_mem_access_sparse()

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 08/26/2016 10:18 AM, Jan Beulich wrote:
>>>> On 26.08.16 at 08:11, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>> +        rc = p2m_set_mem_access(d, _gfn(mao.pfn), arr, mao.nr, start_iter,
>> +                                MEMOP_CMD_MASK, mao.access, 0);
> 
> Please don't pass mao.pfn here when it's meant to be ignore by
> the caller. Use GFN_INVALID instead. And for future extensibility
> please check that the caller put some pre-defined pattern here
> (not sure whether zero is appropriate in this case).

GFN_INVALID has it's own semantics in p2m_set_mem_access():

    /* If request to set default access. */
    if ( gfn_eq(gfn, INVALID_GFN) )
    {
        p2m->default_access = a;
        return 0;
    }

I'll replace the condition with "if ( !arr && gfn_eq(gfn, INVALID_GFN)
)" and use GFN_INVALID in the XENMEM_access_op_set_access_multi (renamed
from XENMEM_access_op_set_access_sparse), as recommended.


Thanks,
Razvan

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