x86/cpu: Fix a F00F bug warning and clean up surrounding code

On x86 SMP systems with the F00F bug present, do_clear_cpu_cap()
rightfully warns that the code clears the X86_BUG_F00F flag after
alternatives have been patched.

X86_BUG_F00F is first cleared in intel_workarounds() and then set for
the affected models. This sequence works fine on the BSP but on AP
bringup, where alternatives have already been patched and clearing the
flag there triggers the warning.

There is no technical reason for clearing the flag before setting it. It
is mainly an artifact of introducing the X86_BUG_F00F flag in

  e2604b49e8a8 ("x86, cpu: Convert F00F bug detection").

Remove the unnecessary clearing of the flag.

While at it, remove the kernel notification and the surrounding logic to
inform the user about the workaround exactly once. If needed, the
presence of the F00F bug can be determined through /proc/cpuinfo.

Additionally, the F00F bug was the last remaining user of clear_cpu_bug().
With no users left, get rid of this helper as well.

  [ bp: Massage commit message. ]

Co-developed-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ahmed S. Darwish <darwi@linutronix.de>
Link: https://patch.msgid.link/20260528184826.3642051-1-sohil.mehta@intel.com

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 3ddc1d33399be9d7ab2dc79bdaaa34b3de9168b4..90680f978d43be93622f905f898bad4f51d8663e 100644 (file)
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -125,7 +125,6 @@ t_no:
 
 #define cpu_has_bug(c, bit)            cpu_has(c, (bit))
 #define set_cpu_bug(c, bit)            set_cpu_cap(c, (bit))
-#define clear_cpu_bug(c, bit)          clear_cpu_cap(c, (bit))
 
 #define static_cpu_has_bug(bit)                static_cpu_has((bit))
 #define boot_cpu_has_bug(bit)          cpu_has_bug(&boot_cpu_data, (bit))

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index f28c0efb7c8f1325b6d4fc99e247bde08f1884c8..abb3984336ebf285d3b6292b6bf50353af46df25 100644 (file)
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -388,24 +388,15 @@ __setup("forcepae", forcepae_setup);
 
 static void intel_workarounds(struct cpuinfo_x86 *c)
 {
-#ifdef CONFIG_X86_F00F_BUG
        /*
         * All models of Pentium and Pentium with MMX technology CPUs
         * have the F0 0F bug, which lets nonprivileged users lock up the
-        * system. Announce that the fault handler will be checking for it.
+        * system. The fault handler always checks for it.
         * The Quark is also family 5, but does not have the same bug.
         */
-       clear_cpu_bug(c, X86_BUG_F00F);
-       if (c->x86_vfm >= INTEL_FAM5_START && c->x86_vfm < INTEL_QUARK_X1000) {
-               static int f00f_workaround_enabled;
-
+       if (IS_ENABLED(CONFIG_X86_F00F_BUG) &&
+           (c->x86_vfm >= INTEL_FAM5_START && c->x86_vfm < INTEL_QUARK_X1000))
                set_cpu_bug(c, X86_BUG_F00F);
-               if (!f00f_workaround_enabled) {
-                       pr_notice("Intel Pentium with F0 0F bug - workaround enabled.\n");
-                       f00f_workaround_enabled = 1;
-               }
-       }
-#endif
 
        /*
         * SEP CPUID bug: Pentium Pro reports SEP but doesn't have it until