Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:
 "This tree includes:

   - a fix that disables the compacted FPU XSAVE format by disabling
     XSAVES support: the fixes are too complex and the breakages
     ABI-affecting, so we want this to be quirked off in a robust way
     and backported, to make sure no broken kernel is exposed to the new
     hardware (which exposure is still very limited).

   - an MCE printk message fix

   - a documentation fix"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu: Disable XSAVES* support for now
  x86/Documentation: Update the contact email for L3 cache index disable functionality
  x86/mce: Fix MCE severity messages

2 files changed, 20 insertions, 2 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index e535533d5ab8..20190bdac9d5 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -708,6 +708,7 @@ static int mce_no_way_out(struct mce *m, char **msg, unsigned long *validp,
                           struct pt_regs *regs)
 {
         int i, ret = 0;
+        char *tmp;
 
         for (i = 0; i < mca_cfg.banks; i++) {
                 m->status = mce_rdmsrl(MSR_IA32_MCx_STATUS(i));
@@ -716,9 +717,11 @@ static int mce_no_way_out(struct mce *m, char **msg, unsigned long *validp,
                         if (quirk_no_way_out)
                                 quirk_no_way_out(i, m, regs);
                 }
-                if (mce_severity(m, mca_cfg.tolerant, msg, true) >=
-                    MCE_PANIC_SEVERITY)
+
+                if (mce_severity(m, mca_cfg.tolerant, &tmp, true) >= MCE_PANIC_SEVERITY) {
+                        *msg = tmp;
                         ret = 1;
+                }
         }
         return ret;
 }
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 009183276bb7..6185d3141219 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -173,6 +173,21 @@ static void init_thread_xstate(void)
                 xstate_size = sizeof(struct i387_fxsave_struct);
         else
                 xstate_size = sizeof(struct i387_fsave_struct);
+
+        /*
+         * Quirk: we don't yet handle the XSAVES* instructions
+         * correctly, as we don't correctly convert between
+         * standard and compacted format when interfacing
+         * with user-space - so disable it for now.
+         *
+         * The difference is small: with recent CPUs the
+         * compacted format is only marginally smaller than
+         * the standard FPU state format.
+         *
+         * ( This is easy to backport while we are fixing
+         *   XSAVES* support. )
+         */
+        setup_clear_cpu_cap(X86_FEATURE_XSAVES);
 }
 
 /*