> From: Natalie Protasevich <protasnb@xxxxxxxxx>
> This patch allows to disable ptc.g. The code used to be in the
> kernel, then was removed in 2.4 since the bug that it was fixing has
> gone away. However, some large system vendors now want this
> capability available through a means that can be controlled by the
> platform in the event that there is an issue with either processor
> or their chipset where global ptc.g is not operational. They want
> the mechanism for future platforms to work around such issues. It
> is also needed for platform makers when they deliberately do not
> use the global cache purge in their chipset implementation. (For
> such cases, Intel provided a SAL table entry to specify if ptc.g is
> allowed and how many).
Hi Natalie,
I still don't understand the need for this patch given my comment to
your last posting and I'd like to know what the actual usage scenario
is.
That said, a few comments on the coding style and patch submission
below. Please make sure to read Documentation/CodingStyle and
Documentation/SubmittingPatches
1) No Signed-off-by: line.
---
+/*
+ * flush_tlb_no_ptcg is called with ptcg_lock locked
+ */
+static inline void
+flush_tlb_no_ptcg (unsigned long start, unsigned long end,
+ unsigned long nbits)
+{
+ extern void smp_send_flush_tlb (void);
Ewwwwwwwww! prototypes within the function :-(
+ atomic_set(&ia64_global_tlb_flush_cpu_count, cpus - 1);
+ smp_send_flush_tlb();
+ /*
+ * Purge local TLB entries. ALAT invalidation is done in ia64_leave_kernel.
+ */
A column is 80 characters, max.
@@ -94,9 +166,17 @@ ia64_global_tlb_purge (struct mm_struct
return;
}
- /* HW requires global serialization of ptc.ga. */
+ /*
+ * HW requires global serialization of ptc.ga, and same does
+ * IPI based implementation of global TLB purge
+ */
spin_lock(&ptcg_lock);
- {
+ if (noptcg) {
+ /*
+ * Handle the case when ptc.ga is not available in HW
+ */
+ flush_tlb_no_ptcg(start, end, nbits);
+ } else {
This just underlines why this should be implemented via the machine
vectors.
diff -puN arch/ia64/kernel/smp.c~ptcg arch/ia64/kernel/smp.c
--- linux-2.6.23-rc5/arch/ia64/kernel/smp.c~ptcg 2007-09-02 23:58:54.000000000 -0700
+++ linux-2.6.23-rc5-nataliep/arch/ia64/kernel/smp.c 2007-09-02 23:59:25.000000000 -0700
@@ -79,6 +79,7 @@ static volatile struct call_data_struct
#define IPI_CALL_FUNC 0
#define IPI_CPU_STOP 1
+#define IPI_FLUSH_TLB 2
#define IPI_KDUMP_CPU_STOP 3
/* This needs to be cacheline aligned because it is written to by *other* CPUs. */
@@ -174,6 +175,48 @@ handle_IPI (int irq, void *dev_id)
unw_init_running(kdump_cpu_freeze, NULL);
break;
#endif
+
+ case IPI_FLUSH_TLB:
+ {
+ extern unsigned long ia64_global_tlb_flush_start,
+ ia64_global_tlb_flush_end, ia64_global_tlb_flush_nbits,
+ ia64_global_tlb_flush_rid;
+ extern atomic_t ia64_global_tlb_flush_cpu_count;
Please, no external prototypes hidden within the function!
Indents are 8 chars - but if you put the extern's in the place where
they belond you won't need the brackets here in the first place.
+ unsigned long saved_rid = ia64_get_rr(ia64_global_tlb_flush_start);
+ unsigned long end = ia64_global_tlb_flush_end;
+ unsigned long start = ia64_global_tlb_flush_start;
+ unsigned long nbits = ia64_global_tlb_flush_nbits;
Again, stick to 80 characters.
+
Gratitious whitespace.
+ /*
+ * Current CPU may be running with different RID so we need to
+ * reload the RID of flushed address. Purging the translation
+ * also needs ALAT invalidation; we do not need "invala" here
+ * since it is done in ia64_leave_kernel.
+ */
More 80 character problems.
+ ia64_srlz_d();
+ if (saved_rid != ia64_global_tlb_flush_rid) {
+ ia64_set_rr(ia64_global_tlb_flush_start, ia64_global_tlb_flush_rid);
Ditto
+ if (saved_rid != ia64_global_tlb_flush_rid) {
+ ia64_set_rr(ia64_global_tlb_flush_start, saved_rid);
And again....
+ ia64_srlz_d();
+ }
+ atomic_dec(&ia64_global_tlb_flush_cpu_count);
+ break;
+ }
default:
printk(KERN_CRIT "Unknown IPI on CPU %d: %lu\n", this_cpu, which);
And again....
-
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