On Thu, Aug 16, 2012 at 04:22:09PM -0700, [email protected] wrote: > > This is a note to let you know that I've just added the patch titled > > xen/p2m: Reserve 8MB of _brk space for P2M leafs when populating back. > > to the 3.4-stable tree which can be found at: > > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > > xen-p2m-reserve-8mb-of-_brk-space-for-p2m-leafs-when-populating-back.patch > and it can be found in the queue-3.4 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <[email protected]> know about it.
Please don't. It should only go in v3.5 back-port tree. Thanks! > > > >From 5bc6f9888db5739abfa0cae279b4b442e4db8049 Mon Sep 17 00:00:00 2001 > From: Konrad Rzeszutek Wilk <[email protected]> > Date: Mon, 30 Jul 2012 10:18:05 -0400 > Subject: xen/p2m: Reserve 8MB of _brk space for P2M leafs when populating > back. > > From: Konrad Rzeszutek Wilk <[email protected]> > > commit 5bc6f9888db5739abfa0cae279b4b442e4db8049 upstream. > > When we release pages back during bootup: > > Freeing 9d-100 pfn range: 99 pages freed > Freeing 9cf36-9d0d2 pfn range: 412 pages freed > Freeing 9f6bd-9f6bf pfn range: 2 pages freed > Freeing 9f714-9f7bf pfn range: 171 pages freed > Freeing 9f7e0-9f7ff pfn range: 31 pages freed > Freeing 9f800-100000 pfn range: 395264 pages freed > Released 395979 pages of unused memory > > We then try to populate those pages back. In the P2M tree however > the space for those leafs must be reserved - as such we use extend_brk. > We reserve 8MB of _brk space, which means we can fit over > 1048576 PFNs - which is more than we should ever need. > > Without this, on certain compilation of the kernel we would hit: > > (XEN) domain_crash_sync called from entry.S > (XEN) CPU: 0 > (XEN) RIP: e033:[<ffffffff818aad3b>] > (XEN) RFLAGS: 0000000000000206 EM: 1 CONTEXT: pv guest > (XEN) rax: ffffffff81a7c000 rbx: 000000000000003d rcx: 0000000000001000 > (XEN) rdx: ffffffff81a7b000 rsi: 0000000000001000 rdi: 0000000000001000 > (XEN) rbp: ffffffff81801cd8 rsp: ffffffff81801c98 r8: 0000000000100000 > (XEN) r9: ffffffff81a7a000 r10: 0000000000000001 r11: 0000000000000003 > (XEN) r12: 0000000000000004 r13: 0000000000000004 r14: 000000000000003d > (XEN) r15: 00000000000001e8 cr0: 000000008005003b cr4: 00000000000006f0 > (XEN) cr3: 0000000125803000 cr2: 0000000000000000 > (XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: e02b cs: e033 > (XEN) Guest stack trace from rsp=ffffffff81801c98: > > .. which is extend_brk hitting a BUG_ON. > > Interestingly enough, most of the time we are not going to hit this > b/c the _brk space is quite large (v3.5): > ffffffff81a25000 B __brk_base > ffffffff81e43000 B __brk_limit > = ~4MB. > > vs earlier kernels (with this back-ported), the space is smaller: > ffffffff81a25000 B __brk_base > ffffffff81a7b000 B __brk_limit > = 344 kBytes. > > where we would certainly hit this and hit extend_brk. > > Note that git commit c3d93f880197953f86ab90d9da4744e926b38e33 > (xen: populate correct number of pages when across mem boundary (v2)) > exposed this bug). > > [v1: Made it 8MB of _brk space instead of 4MB per Jan's suggestion] > > Signed-off-by: Konrad Rzeszutek Wilk <[email protected]> > Signed-off-by: Greg Kroah-Hartman <[email protected]> > > --- > arch/x86/xen/p2m.c | 5 +++++ > 1 file changed, 5 insertions(+) > > --- a/arch/x86/xen/p2m.c > +++ b/arch/x86/xen/p2m.c > @@ -194,6 +194,11 @@ RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MA > * boundary violation will require three middle nodes. */ > RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3); > > +/* When we populate back during bootup, the amount of pages can vary. The > + * max we have is seen is 395979, but that does not mean it can't be more. > + * But some machines can have 3GB I/O holes even. So lets reserve enough > + * for 4GB of I/O and E820 holes. */ > +RESERVE_BRK(p2m_populated, PMD_SIZE * 4); > static inline unsigned p2m_top_index(unsigned long pfn) > { > BUG_ON(pfn >= MAX_P2M_PFN); > > > Patches currently in stable-queue which might be from [email protected] > are > > queue-3.4/xen-p2m-reserve-8mb-of-_brk-space-for-p2m-leafs-when-populating-back.patch > queue-3.4/xen-mark-local-pages-as-foreign-in-the-m2p_override.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
