On 07/06/17 13:06, Paul Durrant wrote: >> -----Original Message----- >> From: Xen-devel [mailto:xen-devel-boun...@lists.xen.org] On Behalf Of >> Paul Durrant >> Sent: 07 June 2017 11:37 >> To: Andrew Cooper <andrew.coop...@citrix.com>; 'Juergen Gross' >> <jgr...@suse.com>; Jan Beulich <jbeul...@suse.com> >> Cc: xen-devel (xen-de...@lists.xenproject.org) <xen- >> de...@lists.xenproject.org>; Julien Grall (julien.gr...@arm.com) >> <julien.gr...@arm.com>; 'Boris Ostrovsky' <boris.ostrov...@oracle.com> >> Subject: Re: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot >> >>> -----Original Message----- >> [snip] >>>>> >>>>> TBH: I really can't see what is wrong with that patch. The only change >>>>> which should be able to break something seems to be the reduction of >>> the >>>>> wakeup stack size to 3kB, but this shouldn't affect booting the system >>>>> at all... >>>>> >>>> Yeah, my next test is going to be increasing the size of the wakeup stack >>> again, but there is really nothing obviously wrong with the patch. >>> >>> My gut feeling is that there is some path through boot (tickled by these >>> two machines) which is clobbering the wrong piece of memory, which was >>> previously safe and is now not, because of the rearrangements here. >>> >>> Debugging these machines is very tricky, because they have no serial or >>> IMPI whatsoever. >>> >> >> It does appear to be a layout issue. If I modify the code to just set >> wakeup_stack to wakeup_stack_start + PAGE_SIZE, so it has the full 4k then I >> still get the problem. However if I then move that code block that includes >> wakeup.S and move it to the end of trampoline.S so that wakup code and >> stack are once again located at the end then the problem goes away. >> > > It appears that it is just the code that needs to go at the end. The > following patch is sufficient to avoid the problem. This may be preferable to > a full reversion...
I believe this is wrong. You risk the wakeup_stack extending into wakeup code and the main reason of the patch is gone, as now the permanent trampoline no longer is on a single page. Juergen > > Paul > > diff --git a/xen/arch/x86/boot/trampoline.S b/xen/arch/x86/boot/trampoline.S > index 4d640f3fcd..7709a782f9 100644 > --- a/xen/arch/x86/boot/trampoline.S > +++ b/xen/arch/x86/boot/trampoline.S > @@ -156,7 +156,7 @@ start64: > movabs $__high_start,%rax > jmpq *%rax > > -#include "wakeup.S" > +ENTRY(wakeup_stack_start) > > /* The first page of trampoline is permanent, the rest boot-time only. */ > /* Reuse the boot trampoline on the 1st trampoline page as stack for wakeup. > */ > @@ -280,3 +280,4 @@ rm_idt: .word 256*4-1, 0, 0 > #include "mem.S" > #include "edd.S" > #include "video.S" > +#include "wakeup.S" > diff --git a/xen/arch/x86/boot/wakeup.S b/xen/arch/x86/boot/wakeup.S > index f9632eef95..d4824b55d5 100644 > --- a/xen/arch/x86/boot/wakeup.S > +++ b/xen/arch/x86/boot/wakeup.S > @@ -173,5 +173,3 @@ bogus_saved_magic: > movw $0x0e00 + 'S', 0xb8014 > jmp bogus_saved_magic > > -/* Stack for wakeup: rest of first trampoline page. */ > -ENTRY(wakeup_stack_start) > >> Paul >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xen.org >> https://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
