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From: Benjamin Romer <benjamin.romer@unisys.com>
To: vgoyal@in.ibm.com
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	linux-kernel@vger.kernel.org
Subject: Re: PATCH: Update disable_IO_APIC to use 8-bit destination field  (X86_64)
Date: Thu, 18 Jan 2007 12:23:54 -0500	[thread overview]
Message-ID: <1169141034.6665.6.camel@ustr-romerbm-2.na.uis.unisys.com> (raw)
In-Reply-To: <20070118080003.GC31860@in.ibm.com>

On Thu, 2007-01-18 at 13:30 +0530, Vivek Goyal wrote:
> On Thu, Jan 18, 2007 at 12:10:55AM -0700, Eric W. Biederman wrote:
> > Vivek Goyal <vgoyal@in.ibm.com> writes:
> > >
> > > Or how about making physical_dest field also 8bit like logical_dest field.
> > > This will work both for 4bit and 8bit physical apic ids at the same time
> > > code becomes more intutive and it is easier to know whether IOAPIC is being
> > > put in physical or destination logical mode.
> > 
> > Exactly what I was trying to suggest.
> > 
> > Looking closer at the code I think it makes sense to just kill the union and
> > stop the discrimination between physical and logical modes and just have a
> > dest field in the structure.  Roughly as you were suggesting at first.
> > 
> > The reason we aren't bitten by this on a regular basis is the normal code
> > path uses logical.logical_dest in both logical and physical modes.
> > Which is a little confusing.
> > 
> > Since there really isn't a distinction to be made we should just stop
> > trying, which will make maintenance easier :)
> > 
> > Currently there are several non-common case users of physical_dest
> > that are probably bitten by this problem under the right
> > circumstances.
> > 
> > So I think we should just make the structure:
> > 
> > struct IO_APIC_route_entry {
> > 	__u32	vector		:  8,
> > 		delivery_mode	:  3,	/* 000: FIXED
> > 					 * 001: lowest prio
> > 					 * 111: ExtINT
> > 					 */
> > 		dest_mode	:  1,	/* 0: physical, 1: logical */
> > 		delivery_status	:  1,
> > 		polarity	:  1,
> > 		irr		:  1,
> > 		trigger		:  1,	/* 0: edge, 1: level */
> > 		mask		:  1,	/* 0: enabled, 1: disabled */
> > 		__reserved_2	: 15;
> > 
> > 	__u32	__reserved_3	: 24,
> > 		__dest		:  8;
> > } __attribute__ ((packed));
> > 
> > And fixup the users.  This should keep us from getting bit by this bug
> > in the future.  Like when people start introducing support for more
> > than 256 cores and the low 24bits start getting used.
> > 
> > Or when someone new starts working on the code and thinks the fact
> > the field name says logical we are actually using the apic in logical
> > mode.
> 
> This makes perfect sense to me. Ben, interested in providing a patch 
> for this?
> 
> Thanks
> Vivek

OK, here's the updated patch that uses the new definition and fixes up
the other places that use it. I built and tested this on the ES7000/ONE
and it works well. :)

-- Ben

diff -ru linux-2.6.19.2-orig/arch/x86_64/kernel/io_apic.c
linux-2.6.19.2/arch/x86_64/kernel/io_apic.c
--- linux-2.6.19.2-orig/arch/x86_64/kernel/io_apic.c	2007-03-18
12:29:52.000000000 -0400
+++ linux-2.6.19.2/arch/x86_64/kernel/io_apic.c	2007-03-18
13:15:26.000000000 -0400
@@ -814,7 +814,7 @@
 		entry.delivery_mode = INT_DELIVERY_MODE;
 		entry.dest_mode = INT_DEST_MODE;
 		entry.mask = 0;				/* enable IRQ */
-		entry.dest.logical.logical_dest = cpu_mask_to_apicid(TARGET_CPUS);
+		entry.__dest = cpu_mask_to_apicid(TARGET_CPUS);
 
 		idx = find_irq_entry(apic,pin,mp_INT);
 		if (idx == -1) {
@@ -832,7 +832,7 @@
 		if (irq_trigger(idx)) {
 			entry.trigger = 1;
 			entry.mask = 1;
-			entry.dest.logical.logical_dest = cpu_mask_to_apicid(TARGET_CPUS);
+			entry.__dest = cpu_mask_to_apicid(TARGET_CPUS);
 		}
 
 		irq = pin_2_irq(idx, apic, pin);
@@ -847,7 +847,7 @@
 			if (vector < 0)
 				continue;
 
-			entry.dest.logical.logical_dest = cpu_mask_to_apicid(mask);
+			entry.__dest = cpu_mask_to_apicid(mask);
 			entry.vector = vector;
 
 			ioapic_register_intr(irq, vector, IOAPIC_AUTO);
@@ -888,7 +888,7 @@
 	 */
 	entry.dest_mode = INT_DEST_MODE;
 	entry.mask = 0;					/* unmask IRQ now */
-	entry.dest.logical.logical_dest = cpu_mask_to_apicid(TARGET_CPUS);
+	entry.__dest = cpu_mask_to_apicid(TARGET_CPUS);
 	entry.delivery_mode = INT_DELIVERY_MODE;
 	entry.polarity = 0;
 	entry.trigger = 0;
@@ -988,18 +988,17 @@
 
 	printk(KERN_DEBUG ".... IRQ redirection table:\n");
 
-	printk(KERN_DEBUG " NR Log Phy Mask Trig IRR Pol"
-			  " Stat Dest Deli Vect:   \n");
+	printk(KERN_DEBUG " NR Dst Mask Trig IRR Pol"
+			  " Stat Dmod Deli Vect:   \n");
 
 	for (i = 0; i <= reg_01.bits.entries; i++) {
 		struct IO_APIC_route_entry entry;
 
 		entry = ioapic_read_entry(apic, i);
 
-		printk(KERN_DEBUG " %02x %03X %02X  ",
+		printk(KERN_DEBUG " %02x %03X ",
 			i,
-			entry.dest.logical.logical_dest,
-			entry.dest.physical.physical_dest
+			entry.__dest
 		);
 
 		printk("%1d    %1d    %1d   %1d   %1d    %1d    %1d    %02X\n",
@@ -1261,8 +1260,7 @@
 		entry.dest_mode       = 0; /* Physical */
 		entry.delivery_mode   = dest_ExtINT; /* ExtInt */
 		entry.vector          = 0;
-		entry.dest.logical.logical_dest =
-					GET_APIC_ID(apic_read(APIC_ID));
+		entry.__dest          = GET_APIC_ID(apic_read(APIC_ID));
 
 		/*
 		 * Add it to the IO-APIC irq-routing table:
@@ -1524,7 +1522,7 @@
 
 	entry1.dest_mode = 0;			/* physical delivery */
 	entry1.mask = 0;			/* unmask IRQ now */
-	entry1.dest.physical.physical_dest = hard_smp_processor_id();
+	entry1.__dest = hard_smp_processor_id();
 	entry1.delivery_mode = dest_ExtINT;
 	entry1.polarity = entry0.polarity;
 	entry1.trigger = 0;
@@ -2092,7 +2090,7 @@
 
 	entry.delivery_mode = INT_DELIVERY_MODE;
 	entry.dest_mode = INT_DEST_MODE;
-	entry.dest.logical.logical_dest = cpu_mask_to_apicid(mask);
+	entry.__dest = cpu_mask_to_apicid(mask);
 	entry.trigger = triggering;
 	entry.polarity = polarity;
 	entry.mask = 1;					 /* Disabled (masked) */
diff -ru linux-2.6.19.2-orig/include/asm-x86_64/io_apic.h
linux-2.6.19.2/include/asm-x86_64/io_apic.h
--- linux-2.6.19.2-orig/include/asm-x86_64/io_apic.h	2007-03-18
12:30:07.000000000 -0400
+++ linux-2.6.19.2/include/asm-x86_64/io_apic.h	2007-03-18
12:58:37.000000000 -0400
@@ -72,31 +72,21 @@
 };
 
 struct IO_APIC_route_entry {
-	__u32	vector		:  8,
-		delivery_mode	:  3,	/* 000: FIXED
-					 * 001: lowest prio
-					 * 111: ExtINT
-					 */
-		dest_mode	:  1,	/* 0: physical, 1: logical */
-		delivery_status	:  1,
-		polarity	:  1,
-		irr		:  1,
-		trigger		:  1,	/* 0: edge, 1: level */
-		mask		:  1,	/* 0: enabled, 1: disabled */
-		__reserved_2	: 15;
-
-	union {		struct { __u32
-					__reserved_1	: 24,
-					physical_dest	:  4,
-					__reserved_2	:  4;
-			} physical;
-
-			struct { __u32
-					__reserved_1	: 24,
-					logical_dest	:  8;
-			} logical;
-	} dest;
+        __u32   vector          :  8,
+                delivery_mode   :  3,   /* 000: FIXED
+                                         * 001: lowest prio
+                                         * 111: ExtINT
+                                         */
+                dest_mode       :  1,   /* 0: physical, 1: logical */
+                delivery_status :  1,
+                polarity        :  1,
+                irr             :  1,
+                trigger         :  1,   /* 0: edge, 1: level */
+                mask            :  1,   /* 0: enabled, 1: disabled */
+                __reserved_2    : 15;
 
+        __u32   __reserved_3    : 24,
+                __dest          :  8;
 } __attribute__ ((packed));
 
 /*


  parent reply	other threads:[~2007-01-18 17:24 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-17 16:46 Benjamin Romer
2007-01-17 19:08 ` Eric W. Biederman
2007-01-18  3:41   ` Vivek Goyal
2007-01-18  4:36     ` Vivek Goyal
2007-01-18  7:10       ` Eric W. Biederman
     [not found]         ` <2 0070118080003.GC31860@in.ibm.com>
2007-01-18  8:00         ` Vivek Goyal
2007-01-18 14:58           ` Benjamin Romer
2007-01-18 17:23           ` Benjamin Romer [this message]
2007-01-18 18:14             ` Eric W. Biederman
     [not found]               ` <1169147619.6665. 11.camel@ustr-romerbm-2.na.uis.unisys.com>
2007-01-18 19:13               ` Benjamin Romer
2007-01-19  3:49                 ` Vivek Goyal
2007-01-19 15:11                   ` Benjamin Romer
2007-01-19 15:43                     ` Randy Dunlap
2007-01-19 17:14                       ` Benjamin Romer
2007-01-19 15:55                     ` Eric W. Biederman

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