Re: [Xen-devel] [PATCH for-4.11 1/2] libxc/x86: fix mapping of the start_info area

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

Ping?

On Thu, Mar 22, 2018 at 09:10:03AM +0000, Roger Pau Monné wrote:
> On Wed, Mar 21, 2018 at 06:09:57PM +0000, Wei Liu wrote:
> > On Wed, Mar 21, 2018 at 02:42:10PM +0000, Roger Pau Monne wrote:
> > > The start_info size calculated in bootlate_hvm is wrong. It should use
> > > HVMLOADER_MODULE_MAX_COUNT instead of dom->num_modules and it doesn't
> > > take into account the size of the modules command line.
> > > 
> > > This is not a problem so far because the actually used amount of
> > > memory doesn't cross a page boundary, and so no page-fault is
> > > triggered.
> > 
> > I get the cmdline bit.
> > 
> > What does it need to be HVMLOADER_MODULE_MAX_COUNT? Isn't better to just
> > map what we need here?
> 
> Because the position of the modules command line is:
> 
> modlist_paddr + sizeof(struct hvm_modlist_entry) * HVMLOADER_MODULE_MAX_COUNT;
> 
> (This is from add_module_to_list).
> 
> So if dom->num_modules < HVMLOADER_MODULE_MAX_COUNT the mapped region
> is smaller that what we might end up using.
> 
> I'm not sure why HVMLOADER_MODULE_MAX_COUNT is used when allocating
> memory (in alloc_magic_pages_hvm) instead of the actual number of
> modules (dom->num_modules), but the proposed change seems to be the
> easier way to fix the mapping issue.
> 
> I've CC'ed the original authors of this code in another thread, but
> got no response.
> 
> Thanks, Roger.
> 
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