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Date:      Mon, 18 Feb 2013 13:44:35 +0100
From:      Svatopluk Kraus <onwahe@gmail.com>
To:        freebsd-current@freebsd.org
Subject:   [patch] i386 pmap sysmaps_pcpu[] atomic access
Message-ID:  <CAFHCsPUVTM9jfrnzY72YsPszLWkg-UaJcycTR4xXcS%2BfPzS1Vg@mail.gmail.com>
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Hi,

   the access to sysmaps_pcpu[] should be atomic with respect to
thread migration. Otherwise, a sysmaps for one CPU can be stolen by
another CPU and the purpose of per CPU sysmaps is broken. A patch is
enclosed.

     Svata

Index: sys/i386/i386/pmap.c
===================================================================
--- sys/i386/i386/pmap.c	(revision 246831)
+++ sys/i386/i386/pmap.c	(working copy)
@@ -4146,11 +4146,11 @@
 {
 	struct sysmaps *sysmaps;

+	sched_pin();
 	sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
 	mtx_lock(&sysmaps->lock);
 	if (*sysmaps->CMAP2)
 		panic("pmap_zero_page: CMAP2 busy");
-	sched_pin();
 	*sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
 	    pmap_cache_bits(m->md.pat_mode, 0);
 	invlcaddr(sysmaps->CADDR2);
@@ -4171,11 +4171,11 @@
 {
 	struct sysmaps *sysmaps;

+	sched_pin();
 	sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
 	mtx_lock(&sysmaps->lock);
 	if (*sysmaps->CMAP2)
 		panic("pmap_zero_page_area: CMAP2 busy");
-	sched_pin();
 	*sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
 	    pmap_cache_bits(m->md.pat_mode, 0);
 	invlcaddr(sysmaps->CADDR2);
@@ -4220,13 +4220,13 @@
 {
 	struct sysmaps *sysmaps;

+	sched_pin();
 	sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
 	mtx_lock(&sysmaps->lock);
 	if (*sysmaps->CMAP1)
 		panic("pmap_copy_page: CMAP1 busy");
 	if (*sysmaps->CMAP2)
 		panic("pmap_copy_page: CMAP2 busy");
-	sched_pin();
 	invlpg((u_int)sysmaps->CADDR1);
 	invlpg((u_int)sysmaps->CADDR2);
 	*sysmaps->CMAP1 = PG_V | VM_PAGE_TO_PHYS(src) | PG_A |
@@ -5072,11 +5072,11 @@
 	vm_offset_t sva, eva;

 	if ((cpu_feature & CPUID_CLFSH) != 0) {
+		sched_pin();
 		sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
 		mtx_lock(&sysmaps->lock);
 		if (*sysmaps->CMAP2)
 			panic("pmap_flush_page: CMAP2 busy");
-		sched_pin();
 		*sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) |
 		    PG_A | PG_M | pmap_cache_bits(m->md.pat_mode, 0);
 		invlcaddr(sysmaps->CADDR2);

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