Re: [PATCH] tools/xenstore: set maximum number of grants needed

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/09/2020 16:28, Wei Liu wrote:
> On Wed, Sep 30, 2020 at 05:23:58PM +0200, Jürgen Groß wrote:
>> On 30.09.20 17:14, Wei Liu wrote:
>>> On Thu, Sep 24, 2020 at 04:36:48PM +0200, Juergen Gross wrote:
>>>> When running as a stubdom Xenstore should set the maximum number of
>>>> grants needed via a call of xengnttab_set_max_grants(), as otherwise
>>>> the number of domains which can be supported will be 128 only (the
>>>> default number of grants supported by Mini-OS).
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>>> ---
>>>> This is a backport candidate IMO.
>>>> ---
>>>>   tools/xenstore/xenstored_domain.c | 2 ++
>>>>   1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/tools/xenstore/xenstored_domain.c 
>>>> b/tools/xenstore/xenstored_domain.c
>>>> index 06359503f0..f740aa02f5 100644
>>>> --- a/tools/xenstore/xenstored_domain.c
>>>> +++ b/tools/xenstore/xenstored_domain.c
>>>> @@ -630,6 +630,8 @@ void domain_init(void)
>>>>    *xgt_handle = xengnttab_open(NULL, 0);
>>>>    if (*xgt_handle == NULL)
>>>>            barf_perror("Failed to open connection to gnttab");
>>>> +  /* Allow max number of domains for mappings. */
>>>> +  xengnttab_set_max_grants(*xgt_handle, DOMID_FIRST_RESERVED);
>>> Why DOMID_FIRST_RESERVED as the count argument? Is the expectation here
>>> xenstored maps one grant per domain?
>> Yes. This is the theoretical maximum.
>>
> In that case:
>
> Acked-by: Wei Liu <wl@xxxxxxx>
>
> I will also add that information to the commit message.

And the comment if possible please.  That's where it will be most useful
to the next person doing a doubletake at this code.  :)

~Andrew