On Tue, Nov 06, 2012 at 01:37:10PM +0000, Jan Beulich wrote: > >>> On 06.11.12 at 13:55, Josh Triplett <[email protected]> wrote: > > On Tue, Nov 06, 2012 at 08:57:06AM +0000, Jan Beulich wrote: > >> The question here is how to properly invalidate that data then: > >> So far I was assuming that clearing the valid bit would be the way > >> to go, as the specification says nothing on e.g. the image address > >> being zero having any specific meaning. I need to do that in Xen, > >> at least for the time being, as I'm not inclined to postpone > >> indefinitely the use of boot services memory for normal memory > >> allocations (which we would have to do if we wanted Dom0 to > >> be able to access the image pointed to here). > > > > This doesn't postpone the use of boot services memory indefinitely; the > > BGRT driver copies the image out, and the kernel then frees boot > > services memory. That does introduce a delay in the use of boot > > services memory, but not an indefinite one. > > If and when Dom0 tells the hypervisor that it's done using that > data is unknown from the hypervisor perspective, so for Xen > this _is_ indefinitely.
Ah, I see. > >> I was quite bad a design decision to allow (and even suggest) > >> the image to live in boot services memory - one can't generally > >> expect the ACPI parser to become available in an OS before > >> setting up memory allocation. To Linux this already has turned > >> out to be a problem, on Xen dealing with this would turn out > >> even more cumbersome. > > > > What problems has this caused? > > None so far - I'm trying to prevent any from occurring. > > Or if you're referring to my use of the term "problems" above - I > was referring to the fact that for this very reason the treatment > of boot services memory had to be changed in Linux. Oh, I definitely agree about the poor design decision of putting the image in boot services memory. I had specifically wondered what problems had occurred in Linux and Xen due to needing the ACPI parser before freeing boot services memory. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
