lkml.org 
[lkml]   [2012]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v4 14/24] xen/arm: initialize grant_table on ARM
    On Fri, 14 Sep 2012, Ian Campbell wrote:
    > On Fri, 2012-09-14 at 15:56 +0100, Stefano Stabellini wrote:
    > > On Fri, 14 Sep 2012, Konrad Rzeszutek Wilk wrote:
    > > > On Fri, Sep 14, 2012 at 12:13:16PM +0100, Stefano Stabellini wrote:
    > > > > Initialize the grant table mapping at the address specified at index 0
    > > > > in the DT under the /xen node.
    > > > > After the grant table is initialized, call xenbus_probe (if not dom0).
    > > >
    > > > So we don't really care about the grant's size then? The DT xen.txt
    > > > talks about it..
    > >
    > > I am assuming that the size of the memory region specified in the device
    > > tree is sufficiently large to map the entire grant table, given that both
    > > the device tree hypervisor entry and the grant table size comes from Xen.
    >
    > Actually, the grant table can grow dynamically under the control of the
    > guest, I think you just pass GNTTABOP_setup_table with some more frames.
    > See drivers/xen/grant_table.c:gnttab_expand().

    gnttab_expand can return error if the new size exceeds
    gnttab_max_grant_frames(), that is implemented using
    GNTTABOP_query_size.


    > > The grant table size is currently queried to Xen directly via an
    > > hypercall (GNTTABOP_query_size). Basically the size in the device tree
    > > is redundant information.
    >
    > This size is the size of the physical address space where the guest
    > could chose map grant table frames. It could be either larger or smaller
    > than the actual grant table. (smaller because the guest could use
    > physical addresses not within this region, if it wanted to for some
    > reason).

    Right.

    What I am saying is that I assume that the memory region specified in
    the device tree is greater or equal than gnttab_max_grant_frames().
    Maybe I should add this to the device tree doc.


    \
     
     \ /
      Last update: 2012-09-14 18:01    [from the cache]
    ©2003-2011 Jasper Spaans