linux-kernel - [PATCH v2 8/9] x86/mm/tlb: Remove UV special case

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Message-Id: <20190702235151.4377-9-namit@vmware.com>
Date:   Tue,  2 Jul 2019 16:51:50 -0700
From:   Nadav Amit <namit@...are.com>
To:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Nadav Amit <namit@...are.com>,
        Dave Hansen <dave.hansen@...el.com>
Subject: [PATCH v2 8/9] x86/mm/tlb: Remove UV special case

SGI UV support is outdated and not maintained, and it is not clear how
it performs relatively to non-UV. Remove the code to simplify the code.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Suggested-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Nadav Amit <namit@...are.com>
---
 arch/x86/mm/tlb.c | 25 -------------------------
 1 file changed, 25 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index b47a71820f35..64afe1215495 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -689,31 +689,6 @@ void native_flush_tlb_multi(const struct cpumask *cpumask,
 		trace_tlb_flush(TLB_REMOTE_SEND_IPI,
 				(info->end - info->start) >> PAGE_SHIFT);
 
-	if (is_uv_system()) {
-		/*
-		 * This whole special case is confused.  UV has a "Broadcast
-		 * Assist Unit", which seems to be a fancy way to send IPIs.
-		 * Back when x86 used an explicit TLB flush IPI, UV was
-		 * optimized to use its own mechanism.  These days, x86 uses
-		 * smp_call_function_many(), but UV still uses a manual IPI,
-		 * and that IPI's action is out of date -- it does a manual
-		 * flush instead of calling flush_tlb_func_remote().  This
-		 * means that the percpu tlb_gen variables won't be updated
-		 * and we'll do pointless flushes on future context switches.
-		 *
-		 * Rather than hooking native_flush_tlb_multi() here, I think
-		 * that UV should be updated so that smp_call_function_many(),
-		 * etc, are optimal on UV.
-		 */
-		flush_tlb_func_local(info);
-
-		cpumask = uv_flush_tlb_others(cpumask, info);
-		if (cpumask)
-			smp_call_function_many(cpumask, flush_tlb_func_remote,
-					       (void *)info, 1);
-		return;
-	}
-
 	/*
 	 * If no page tables were freed, we can skip sending IPIs to
 	 * CPUs in lazy TLB mode. They will flush the CPU themselves
-- 
2.17.1