[PATCH v3 1/3] x86/cpu/intel: Don't clear X86_BUG_F00F before setting it

[Sohil Mehta]

From: Richard Weinberger <richard@xxxxxx>

On x86 SMP systems with the F00F bug present, the following warning
occurs for each AP:

  WARNING: arch/x86/kernel/cpu/cpuid-deps.c:126 at do_clear_cpu_cap+0xb4/0x110
  Call Trace:
   clear_cpu_cap+0x8/0x10
   init_intel+0x1b/0x4b0
   identify_cpu+0x154/0x750
   identify_secondary_cpu+0x3d/0x90
   start_secondary+0x6b/0xf0
   startup_32_smp+0x151/0x160

The X86_BUG_F00F flag 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, clearing the
flag triggers the warning.

There is no technical reason for clearing the flag before setting it.
It is mainly an artifact of the introduction of X86_BUG_F00F in commit
e2604b49e8a8 ("x86, cpu: Convert F00F bug detection"). Remove the
unnecessary clearing of the flag.

Note that the fixes tag references a recent commit that introduced the
warning rather than the old commit that converted F00F bug detection to
use clear_cpu_bug().

Fixes: ee8962082a44 ("x86/alternatives: Catch late X86_FEATURE modifiers")
Signed-off-by: Richard Weinberger <richard@xxxxxx>
[sohil: reworded the commit message]
Signed-off-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>
Reviewed-by: Ahmed S. Darwish <darwi@xxxxxxxxxxxxx>
---
v3:
 - Picked up Ahmed's review tag.
v2:
 - Reworded commit message to clarify the issue.
---
 arch/x86/kernel/cpu/intel.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index f28c0efb7c8f..e957c5a1501c 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -395,7 +395,6 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
 	 * system. Announce that the fault handler will be checking 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;
 
-- 
2.43.0