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From: Helge Deller <deller@gmx.de>
To: linux-parisc@vger.kernel.org,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	John David Anglin <dave.anglin@bell.net>
Subject: [PATCH] parisc: speed up flush_tlb_all_local with qemu
Date: Mon, 12 Aug 2019 19:13:20 +0200
Message-ID: <20190812171320.GA28951@ls3530.fritz.box> (raw)

When started in qemu, we know that qemu will drop all local TLB entries
on any pxtlbe instruction. So, if we detect qemu, replace the whole
flush_tlb_all_local function by one pdtlbe instruction.

Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/kernel/pacache.S b/arch/parisc/kernel/pacache.S
index df46b0e5a915..fa092ed1e837 100644
--- a/arch/parisc/kernel/pacache.S
+++ b/arch/parisc/kernel/pacache.S
@@ -174,6 +174,15 @@ fdtdone:

 2:      bv		%r0(%r2)
 	nop
+
+	/*
+	 * When running in qemu, drop whole flush_tlb_all_local function and
+	 * replace by one pdtlbe instruction, for which QEMU will drop all
+	 * local TLB entries.
+	 */
+3:	pdtlbe		%r0(%sr1,%r0)
+	bv,n		%r0(%r2)
+	ALTERNATIVE_CODE(flush_tlb_all_local, 2, ALT_COND_RUN_ON_QEMU, 3b)
 ENDPROC_CFI(flush_tlb_all_local)

 	.import cache_info,data

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