Messages in this thread Patch in this message | | | Date | Sun, 28 Dec 2014 12:12:02 +0100 | From | Juergen Gross <> | Subject | Re: [BISECTED] 3.19-rc1 regression - kernel does not load in GRUB 0.97 (GRUB Legacy) |
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On 12/28/2014 08:20 AM, Пламен Петров wrote: >> -----Original Message----- >> From: Juergen Gross [mailto:jgross@suse.com] >> Sent: Saturday, December 27, 2014 3:48 PM >> To: Пламен Петров; linux-kernel@vger.kernel.org >> Cc: 'Thomas Gleixner' >> Subject: Re: [BISECTED] 3.19-rc1 regression - kernel does not load in GRUB >> 0.97 (GRUB Legacy) >> >> On 12/24/2014 01:28 AM, Пламен Петров wrote: >>> Hello! >>> >>> I use GRUB Legacy bootloader (version 0.97) on a couple machines, and >>> where 3.18.x loads fine, 3.19-rc1 does not. >>> >>> While compiling I used the attached .config file accompanied by "make >>> olddefconfig" >> >> Can you tell me something about the hardware (processor model)? >> You are not booting the system under VMWare by any chance? > > As a matter of fact - I am compiling in a VMware Player (6.0.3 > build-1895310) virtual machine, boot testing there, and then if everything > is OK, I transfer the monolithic kernel produced on 3 virtual machines that > run on EXSi and 2 actual servers. So along those lines - the failing > 3.19-rc1 never saw actual hardware - it was all tested (and bisected) inside > a VM.
Thanks. VMWare having problems with my patch is a known issue. I've already sent a patch working around that issue (VMWare has a bug emulating the PAT MSR). You can either use that patch (attached for your convenience) or use the "nopat" option.
Juergen
From 4b65fb80338c71673cabfa9fa9b0f80f5a4bc320 Mon Sep 17 00:00:00 2001 From: Juergen Gross <jgross@suse.com> Date: Tue, 16 Dec 2014 07:43:51 +0100 Subject: [PATCH] x86: don't rely on VMWare emulating PAT MSR correctly
VMWare seems not to emulate the PAT MSR correctly: reaeding MSR_IA32_CR_PAT returns 0 even after writing another value to it.
Detect this bug and don't use the read value if it is 0.
Commit bd809af16e3ab1f8d55b3e2928c47c67e2a865d2 ("x86: Enable PAT to use cache mode translation tables") triggers this VMWare bug when the kernel is booted as a VMWare guest.
Reported-by: Jongman Heo <jongman.heo@samsung.com> Signed-off-by: Juergen Gross <jgross@suse.com> Tested-by: Jongman Heo <jongman.heo@samsung.com> --- arch/x86/mm/pat.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index edf299c..7ac6869 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -234,8 +234,13 @@ void pat_init(void) PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC); /* Boot CPU check */ - if (!boot_pat_state) + if (!boot_pat_state) { rdmsrl(MSR_IA32_CR_PAT, boot_pat_state); + if (!boot_pat_state) { + pat_disable("PAT read returns always zero, disabled."); + return; + } + } wrmsrl(MSR_IA32_CR_PAT, pat); -- 2.1.2
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