On Tue, Dec 17, 2019 at 12:26:24PM +0000, Andrew Cooper wrote: > On 17/12/2019 12:18, Roger Pau Monné wrote: > > On Tue, Dec 17, 2019 at 12:06:01PM +0000, Andrew Cooper wrote: > >> On 17/12/2019 11:52, Roger Pau Monné wrote: > >>> On Fri, Dec 13, 2019 at 07:04:32PM +0000, Andrew Cooper wrote: > >>>> The trampoline has already set up the idle pagetables (which are the > >>>> correct > >>>> ones to use), and sanitised the flags state. > >>> I wonder why do we have wakeup.S and wakeup_prot.S, it would be easier > >>> to follow if it all was in the same file IMO. > >> wakeup.S is the 16bit entry point, and lives in the trampoline below 1M. > >> > >> wakeup_prot.S is a bit of logic which lives in the main hypervisor. > >> > >> The naming could probably do with some improvement, but they can't > >> feasibly be part of the same file. > > Hm, I'm not sure I follow. Isn't this trampoline copied by Xen in a > > suitable position below the 1M boundary, and hence could use symbols > > in order to figure out which part to copy? > > > > Ie: both the low and the high part could live in the same file as long > > as Xen knows how to differentiate those and which chunk needs > > positioning below 1M? > > There is one trampoline.S (and trampoline.o) which gathers together > various files (including wakeup.S) to construct the trampoline.
Oh, I see it's all included to make a single unit, and the symbols used to mark the start and end of the trampoline chunk are defined outside of the included file. > It is not something which can be constructed simply by putting code/data > in the requisite sections. There are two main entrypoints, one with a > 4k alignment requirement, one with 16 byte alignment, and we split the > trampoline into two parts - one which is BSP-only and is several pages > in size, and one which is post-boot which is only a single page. Given the size of s3_resume I would guess there's space in that single page to fit it, but since it doesn't need to live below the 1M boundary it could be seen as a waste. Anyway, leaving it as-is is fine since placing it in wakeup.S would be a waste of space or require some restructuring of how the trampoline code is assembled. Thanks, Roger. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
