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[v2,04/17] x86/cpu/intel: Fix the movsl alignment preference for extended Families

Message ID 20250211194407.2577252-5-sohil.mehta@intel.com
State New
Headers show
Series Prepare for new Intel Family numbers | expand

Commit Message

Sohil Mehta Feb. 11, 2025, 7:43 p.m. UTC 
The alignment preference for 32-bit movsl based bulk memory move has
been 8-byte for a long time. However this preference is only set for
Family 6 and 15 processors.

Extend the preference to upcoming Family numbers 18 and 19 to maintain
legacy behavior. Also, use a VFM based check instead of switching based
on Family numbers. Refresh the comment to reflect the new check.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>

---

v2: Split the patch into two parts. Update commit message.

---
 arch/x86/kernel/cpu/intel.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 3dce22f00dc3..e5f34a90963e 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -449,23 +449,16 @@  static void intel_workarounds(struct cpuinfo_x86 *c)
 	    (c->x86_stepping < 0x6 || c->x86_stepping == 0xb))
 		set_cpu_bug(c, X86_BUG_11AP);
 
-
 #ifdef CONFIG_X86_INTEL_USERCOPY
 	/*
-	 * Set up the preferred alignment for movsl bulk memory moves
+	 * movsl bulk memory moves can be slow when source and dest are not
+	 * both 8-byte aligned. PII/PIII only like movsl with 8-byte alignment.
+	 *
+	 * Set the preferred alignment for Pentium Pro and newer processors, as
+	 * it has only been tested on these.
 	 */
-	switch (c->x86) {
-	case 4:		/* 486: untested */
-		break;
-	case 5:		/* Old Pentia: untested */
-		break;
-	case 6:		/* PII/PIII only like movsl with 8-byte alignment */
+	if (c->x86_vfm >= INTEL_PENTIUM_PRO)
 		movsl_mask.mask = 7;
-		break;
-	case 15:	/* P4 is OK down to 8-byte alignment */
-		movsl_mask.mask = 7;
-		break;
-	}
 #endif
 
 	intel_smp_check(c);