Re: Boot regression with bacf6b499e11 ("x86/mm: Use a struct to reduce parameters for SME PGD mapping") on top of -rc8
From: Laura Abbott
Date: Sat Jan 20 2018 - 02:03:41 EST
On 01/19/2018 10:57 PM, Laura Abbott wrote:
On 01/19/2018 10:15 PM, Tom Lendacky wrote:
On 1/19/2018 11:25 PM, Gabriel C wrote:
2018-01-20 5:02 GMT+01:00 Laura Abbott <labbott@xxxxxxxxxx>:
On 01/19/2018 06:23 PM, Gabriel C wrote:
2018-01-20 2:23 GMT+01:00 Laura Abbott <labbott@xxxxxxxxxx>:
Hi,
Hi ,
Fedora got multiple reports of an early bootup crash post -rc8.
Bisection showed bacf6b499e11 ("x86/mm: Use a struct to reduce
parameters for SME PGD mapping") . It doesn't revert cleanly
but if I revert the few other changes in arch/x86/mm/mem_encrypt.c
as well it boots up fine.
Annoyingly, I can't seem to get any actual kernel logs even with
earlyprintk. It just reboots immediately (triple fault?). This
happens on both of my Lenovo machines and I can ask other reporters
for details as well.
I tested these patches on 2 Lenovo Ideapad both with Skylake CPUs
on a older dual Xeon box , on 2 Toshibas with AMD APUs , on a RYZEN
box ,
on dual EPYC box .. ofc on EPYC with mem_encrypt=on on the Intel CPUs
disabled.
Also tested on top 4.14.13 , 4.14.14 as well on top 4.15.0-rc7 and on
current master/rc8++ without to see something like this.
Also we pushed these patches on 4.14.13/14 and didn't got any reports
about
something like this.
What Lenovo boxes are these ? maybe I find one to reproduce.
$ git bisect log
# bad: [ec835f8104a21f4d4eeb9d316ee71d2b4a7f00de] Merge tag
'trace-v4.15-rc4-3' of
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
# good: [a8750ddca918032d6349adbf9a4b6555e7db20da] Linux 4.15-rc8
git bisect start 'origin/master' 'v4.15-rc8'
# bad: [79683f80e4f07dba13cc08d0ebcf5c7b0aa1bf68] Merge tag
'mmc-v4.15-rc2-3' of
git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc
git bisect bad 79683f80e4f07dba13cc08d0ebcf5c7b0aa1bf68
# good: [161f72ed6dbe7fb176585091d3b797125d310399] Merge tag
'mac80211-for-davem-2018-01-15' of
git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211
git bisect good 161f72ed6dbe7fb176585091d3b797125d310399
# good: [88dc7fca18001fd883e5ace775afa316b68c8f2c] Merge branch
'x86-pti-for-linus' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 88dc7fca18001fd883e5ace775afa316b68c8f2c
# bad: [d47924417319e3b6a728c0b690f183e75bc2a702] x86/intel_rdt/cqm:
Prevent
use after free
git bisect bad d47924417319e3b6a728c0b690f183e75bc2a702
# good: [fc90ccfd286eabb05ec54521367df8663cf0bbbf] Revert "x86/apic:
Remove
init_bsp_APIC()"
git bisect good fc90ccfd286eabb05ec54521367df8663cf0bbbf
# bad: [bacf6b499e11760aef73a3bb5ce4e5eea74a3fd4] x86/mm: Use a
struct to
reduce parameters for SME PGD mapping
git bisect bad bacf6b499e11760aef73a3bb5ce4e5eea74a3fd4
# good: [1303880179e67c59e801429b7e5d0f6b21137d99] x86/mm: Clean up
register
saving in the __enc_copy() assembly code
git bisect good 1303880179e67c59e801429b7e5d0f6b21137d99
# first bad commit: [bacf6b499e11760aef73a3bb5ce4e5eea74a3fd4]
x86/mm:
Use a
struct to reduce parameters for SME PGD mapping
Configuration is at
https://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git/commit/?h=rawhide
Note that I do think this is something in the Fedora configuration
because a generic "make defconfig" booted just fine.
But maybe some of the Fedora patches ?
Can you try an kernel with the config but without any patches ?
Or a defconfig and just enable CONFIG_AMD_MEM_ENCRYPT ?
The bisect was a vanilla kernel without Fedora patches.
Ok . I did an build ( v4.15-rc8-225-g8dd903d2cf7b ) on my AMD
Workstation ( EPYC CPU )
I've tried multiple config combinations on my EPYC system and have not
been able to reproduce this issue and have not had any boot issues with
mem_encrypt=on or mem_encrypt=off. I don't have access to a non-AMD box
at the moment, but I'm really scratching my head on this one.
 with your 64bit config and one on the Ideapad ( Intel i7-6498DU ) ..
I disabled Selinux since I don't use it here and module signing.
Also with your config my serial setup won't work and the kernel hangs
but mem_encrypt=on/off works just fine.
If your using the EPYC serial device and you haven't enabled legacy
serial device support (if your BIOS supports that), then you're using
it as a platform device. The fedora config has not set the
CONFIG_X86_AMD_PLATFORM_DEVICE setting so you won't get the module
to load and give you serial output.
I'm confused when you say the kernel hangs but mem_encrypt=on/off works
just fine, can you explain that a bit more?
Also I notice on the Workstation it takes forever to boot untill
'DMA-API' reports out-of-memory
( dunno how much memory it need but the box has 128GB of RAM )..
The machines I have are a Lenovo X1 Carbon and a Lenovo T470s.
A Lenovo X220 ThinkPad also reported the problem.
If I comment out sme_encrypt_kernel it boots:
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 7ba5d819ebe3..443ef5d3f1fa 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -158,7 +158,7 @@ unsigned long __head __startup_64(unsigned long
physaddr,
ÂÂÂÂÂÂÂ *p += load_delta - sme_get_me_mask();
ÂÂÂÂÂÂÂ /* Encrypt the kernel and related (if SME is active) */
-ÂÂÂÂÂÂ sme_encrypt_kernel(bp);
+ÂÂÂÂÂÂ //sme_encrypt_kernel(bp);
ÂÂÂÂÂÂÂ /*
ÂÂÂÂÂÂÂÂ * Return the SME encryption mask (if SME is active) to be used
as a
Interestingly, I tried to print the values in sme_active
(sme_me_mask , sev_enabled) followed by a return at the
very start of sme_encrypt_kernel and that rebooted as well,
vs booting if I just kept the return. sme_me_mask and
sev_enabled are explicitly marked as being in .data,
is it possible they are ending up in a section that isn't
yet mapped or did I hit print too early?
Thanks,
Laura
One last note: This was built with gcc 7.2.1