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authorBruce Ashfield <bruce.ashfield@windriver.com>2016-04-01 20:09:23 -0400
committerRichard Purdie <richard.purdie@linuxfoundation.org>2016-04-03 15:51:37 +0100
commit5559301cdfc5b1662be295fbbd044757c21e0418 (patch)
tree514204991d73036ae4f68eb0bfdcab84ca17f2f6
parent686c74f9b45eaf7fe1750b318e930520f82ea17a (diff)
downloadpoky-5559301cdfc5b1662be295fbbd044757c21e0418.tar.gz
Revert "linux-yocto: Work around PAT issue on qemux86"
This reverts commit 94abdb2eea610b174064978d2fb8354a6231fc0c. (From OE-Core rev: c36d6c16bbabb7131e795ff71f84b92834f0306f) Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
-rw-r--r--meta/recipes-kernel/linux/linux-yocto/0001-Fix-qemux86-pat-issue.patch100
-rw-r--r--meta/recipes-kernel/linux/linux-yocto_4.4.bb2
2 files changed, 0 insertions, 102 deletions
diff --git a/meta/recipes-kernel/linux/linux-yocto/0001-Fix-qemux86-pat-issue.patch b/meta/recipes-kernel/linux/linux-yocto/0001-Fix-qemux86-pat-issue.patch
deleted file mode 100644
index 367d9b4ace..0000000000
--- a/meta/recipes-kernel/linux/linux-yocto/0001-Fix-qemux86-pat-issue.patch
+++ /dev/null
@@ -1,100 +0,0 @@
1From 9bfb2c711f66fc8eb6482f5ca6ea33c2ec1d792f Mon Sep 17 00:00:00 2001
2From: Richard Purdie <richard.purdie@linuxfoundation.org>
3Date: Sat, 13 Feb 2016 17:36:23 +0000
4Subject: [PATCH] Fix qemux86 pat issue
5
6on qemux86, X doesn't start and there is
7a backtrace in the logs:
8
9x86/PAT: Xorg:705 map pfn expected mapping type uncached-minus for [mem 0xfd000000-0xfdffffff], got write-combining
10------------[ cut here ]------------
11WARNING: CPU: 0 PID: 705 at /media/build1/poky/build/tmp/work-shared/qemux86/kernel-source/arch/x86/mm/pat.c:985 untrack_pfn+0xaf/0xc0()
12Modules linked in: uvesafb
13CPU: 0 PID: 705 Comm: Xorg Not tainted 4.4.1-yocto-standard #1
14Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
15 00000000 00000000 cf14dd78 c1397ab2 00000000 cf14dda8 c1051477 c1aa4f6c
16 00000000 000002c1 c1a9fa4c 000003d9 c104b98f c104b98f cf244000 b6355000
17 00000000 cf14ddb8 c1051552 00000009 00000000 cf14dde0 c104b98f cf14ddd0
18Call Trace:
19 [<c1397ab2>] dump_stack+0x4b/0x79
20 [<c1051477>] warn_slowpath_common+0x87/0xc0
21 [<c104b98f>] ? untrack_pfn+0xaf/0xc0
22 [<c104b98f>] ? untrack_pfn+0xaf/0xc0
23 [<c1051552>] warn_slowpath_null+0x22/0x30
24 [<c104b98f>] untrack_pfn+0xaf/0xc0
25 [<c104d54c>] ? kmap_atomic_prot+0x3c/0xf0
26 [<c114e17f>] unmap_single_vma+0x4ef/0x500
27 [<c114f007>] unmap_vmas+0x37/0x50
28 [<c1154f8f>] exit_mmap+0x5f/0xf0
29 [<c104eedd>] mmput+0x2d/0xb0
30 [<c105009c>] copy_process+0xd2c/0x13c0
31 [<c1050892>] _do_fork+0x82/0x340
32 [<c105f2d1>] ? SyS_rt_sigaction+0x51/0xa0
33 [<c1050c3c>] SyS_clone+0x2c/0x30
34 [<c1001a03>] do_syscall_32_irqs_on+0x53/0xb0
35 [<c189a94a>] entry_INT80_32+0x2a/0x2a
36---[ end trace be3e0a61097feddc ]---
37x86/PAT: Xorg:705 map pfn expected mapping type uncached-minus for [mem 0xfd000000-0xfdffffff], got write-combining
38
39The entry in question is setup by uvesafb which in its
40uvesafb_ioremap() function calls ioremap_wc().
41
42It appears that Xorg mmaps this from userspace, then later does a
43fork() to execute a utility. At this point, when creating the vmas for
44the new process, the pat code says "eeek!" as the protection mode for
45the new vmas don't match the old one, returns -EINVAL, the process dies
46and X goes with it.
47
48There are a few hammers we can hit this with, we can boot with "nopat"
49option which makes the problem go away, or turn off CONFIG_X86_PAT. No
50surprises there. Changing uvesafb to use mtrr=0 doesn't help since the
51ioremap_wc call still happens.
52
53The real issue is the "expected mapping type uncached-minus for got
54write-combining" message, it all goes wrong from there.
55
56Upon looking at the code and scratching my head for a long while, I
57notice that there are two ways of representing the protection mode
58data, "enum page_cache_mode" and "pgprot_t & _PAGE_CACHE_MASK".
59
60The exact meaning of pgprot_t depends on which CPU you're running,
61older CPUs have errata meaning only a small number of bits can be used.
62The exact mapping table is determined by __cachemode2pte_tbl and is
63updated at boot by calls from update_cache_mode_entry().
64
65The result of this if you map enum -> pgprot_t, then try to do pgprot_t
66-> enum, you can get different values since its not a 1:1 mapping.
67
68This means the comparison in reserve_pfn_range() where it does "pcm !=
69want_pcm" isn't correct and can trigger even in cases where there isn't
70a problem.
71
72This can be "fixed" by doing cachemode2protval(pcm) !=
73cachemode2protval(want_pcm) and checking whether the protection bits
74match, rather than the enum values, since in reality this is what we
75really care about. With that change, X boots up just fine.
76
77We don't see this on qemux86-64 since that has more PAT bits working
78and hence the values map correctly.
79
80Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
81---
82 arch/x86/mm/pat.c | 2 +-
83 1 file changed, 1 insertion(+), 1 deletion(-)
84
85diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
86index 031782e..11064fb 100644
87--- a/arch/x86/mm/pat.c
88+++ b/arch/x86/mm/pat.c
89@@ -833,7 +833,7 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
90 if (ret)
91 return ret;
92
93- if (pcm != want_pcm) {
94+ if (cachemode2protval(pcm) != cachemode2protval(want_pcm)) {
95 if (strict_prot ||
96 !is_new_memtype_allowed(paddr, size, want_pcm, pcm)) {
97 free_memtype(paddr, paddr + size);
98--
992.5.0
100
diff --git a/meta/recipes-kernel/linux/linux-yocto_4.4.bb b/meta/recipes-kernel/linux/linux-yocto_4.4.bb
index 49038caf94..5280777f80 100644
--- a/meta/recipes-kernel/linux/linux-yocto_4.4.bb
+++ b/meta/recipes-kernel/linux/linux-yocto_4.4.bb
@@ -40,5 +40,3 @@ KERNEL_FEATURES_append_qemuall=" cfg/virtio.scc"
40KERNEL_FEATURES_append_qemux86=" cfg/sound.scc cfg/paravirt_kvm.scc" 40KERNEL_FEATURES_append_qemux86=" cfg/sound.scc cfg/paravirt_kvm.scc"
41KERNEL_FEATURES_append_qemux86-64=" cfg/sound.scc cfg/paravirt_kvm.scc" 41KERNEL_FEATURES_append_qemux86-64=" cfg/sound.scc cfg/paravirt_kvm.scc"
42KERNEL_FEATURES_append = " ${@bb.utils.contains("TUNE_FEATURES", "mx32", " cfg/x32.scc", "" ,d)}" 42KERNEL_FEATURES_append = " ${@bb.utils.contains("TUNE_FEATURES", "mx32", " cfg/x32.scc", "" ,d)}"
43
44SRC_URI_append = " file://0001-Fix-qemux86-pat-issue.patch"