diff options
| author | Dave Hansen <dave.hansen@linux.intel.com> | 2016-07-20 19:45:51 (GMT) |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-07-21 16:18:45 (GMT) |
| commit | ec3ed4a2104b8d1ab8da2db5b1221b2ba8a7a6e1 (patch) | |
| tree | 2889b08cebb04dfb937b9915d3ae31a683dc512e /arch/x86/kernel/fpu | |
| parent | b8be15d588060a03569ac85dc4a0247460988f5b (diff) | |
| download | linux-ec3ed4a2104b8d1ab8da2db5b1221b2ba8a7a6e1.tar.xz | |
x86/fpu: Do not BUG_ON() in early FPU code
I don't think it is really possible to have a system where CPUID
enumerates support for XSAVE but that it does not have FP/SSE
(they are "legacy" features and always present).
But, I did manage to hit this case in qemu when I enabled its
somewhat shaky XSAVE support. The bummer is that the FPU is set
up before we parse the command-line or have *any* console support
including earlyprintk. That turned what should have been an easy
thing to debug in to a bit more of an odyssey.
So a BUG() here is worthless. All it does it guarantee that
if/when we hit this case we have an empty console. So, remove
the BUG() and try to limp along by disabling XSAVE and trying to
continue. Add a comment on why we are doing this, and also add
a common "out_disable" path for leaving fpu__init_system_xstate().
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160720194551.63BB2B58@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/fpu')
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 3169bca..680049a 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -714,8 +714,13 @@ void __init fpu__init_system_xstate(void) xfeatures_mask = eax + ((u64)edx << 32); if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { + /* + * This indicates that something really unexpected happened + * with the enumeration. Disable XSAVE and try to continue + * booting without it. This is too early to BUG(). + */ pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask); - BUG(); + goto out_disable; } xfeatures_mask &= fpu__get_supported_xfeatures_mask(); @@ -723,11 +728,8 @@ void __init fpu__init_system_xstate(void) /* Enable xstate instructions to be able to continue with initialization: */ fpu__init_cpu_xstate(); err = init_xstate_size(); - if (err) { - /* something went wrong, boot without any XSAVE support */ - fpu__init_disable_system_xstate(); - return; - } + if (err) + goto out_disable; /* * Update info used for ptrace frames; use standard-format size and no @@ -744,6 +746,11 @@ void __init fpu__init_system_xstate(void) xfeatures_mask, fpu_kernel_xstate_size, boot_cpu_has(X86_FEATURE_XSAVES) ? "compacted" : "standard"); + return; + +out_disable: + /* something went wrong, try to boot without any XSAVE support */ + fpu__init_disable_system_xstate(); } /* |