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authorKevin D. Kissell <kevink@paralogos.com>2008-09-09 21:35:01 +0200
committerRalf Baechle <ralf@linux-mips.org>2008-10-03 17:58:58 +0100
commitd2bb01b042a38219fbddaafc214c5beb96248d2f (patch)
tree6a0380166400d7ad2b61dead8dab933ba8d43d6a /include/asm-mips
parent9cc123631b6630948eb5059d218f44424888daa7 (diff)
downloadblackbird-op-linux-d2bb01b042a38219fbddaafc214c5beb96248d2f.tar.gz
blackbird-op-linux-d2bb01b042a38219fbddaafc214c5beb96248d2f.zip
[MIPS] SMTC: Close tiny holes in the SMTC IPI replay system.
Signed-off-by: Kevin D. Kissell <kevink@paralogos.com> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'include/asm-mips')
-rw-r--r--include/asm-mips/stackframe.h72
1 files changed, 61 insertions, 11 deletions
diff --git a/include/asm-mips/stackframe.h b/include/asm-mips/stackframe.h
index 051e1af0bb95..4c37c4e5f72e 100644
--- a/include/asm-mips/stackframe.h
+++ b/include/asm-mips/stackframe.h
@@ -297,14 +297,31 @@
#ifdef CONFIG_MIPS_MT_SMTC
.set mips32r2
/*
- * This may not really be necessary if ints are already
- * inhibited here.
+ * We need to make sure the read-modify-write
+ * of Status below isn't perturbed by an interrupt
+ * or cross-TC access, so we need to do at least a DMT,
+ * protected by an interrupt-inhibit. But setting IXMT
+ * also creates a few-cycle window where an IPI could
+ * be queued and not be detected before potentially
+ * returning to a WAIT or user-mode loop. It must be
+ * replayed.
+ *
+ * We're in the middle of a context switch, and
+ * we can't dispatch it directly without trashing
+ * some registers, so we'll try to detect this unlikely
+ * case and program a software interrupt in the VPE,
+ * as would be done for a cross-VPE IPI. To accomodate
+ * the handling of that case, we're doing a DVPE instead
+ * of just a DMT here to protect against other threads.
+ * This is a lot of cruft to cover a tiny window.
+ * If you can find a better design, implement it!
+ *
*/
mfc0 v0, CP0_TCSTATUS
ori v0, TCSTATUS_IXMT
mtc0 v0, CP0_TCSTATUS
_ehb
- DMT 5 # dmt a1
+ DVPE 5 # dvpe a1
jal mips_ihb
#endif /* CONFIG_MIPS_MT_SMTC */
mfc0 a0, CP0_STATUS
@@ -325,17 +342,50 @@
*/
LONG_L v1, PT_TCSTATUS(sp)
_ehb
- mfc0 v0, CP0_TCSTATUS
+ mfc0 a0, CP0_TCSTATUS
andi v1, TCSTATUS_IXMT
- /* We know that TCStatua.IXMT should be set from above */
- xori v0, v0, TCSTATUS_IXMT
- or v0, v0, v1
- mtc0 v0, CP0_TCSTATUS
- _ehb
- andi a1, a1, VPECONTROL_TE
+ bnez v1, 0f
+
+/*
+ * We'd like to detect any IPIs queued in the tiny window
+ * above and request an software interrupt to service them
+ * when we ERET.
+ *
+ * Computing the offset into the IPIQ array of the executing
+ * TC's IPI queue in-line would be tedious. We use part of
+ * the TCContext register to hold 16 bits of offset that we
+ * can add in-line to find the queue head.
+ */
+ mfc0 v0, CP0_TCCONTEXT
+ la a2, IPIQ
+ srl v0, v0, 16
+ addu a2, a2, v0
+ LONG_L v0, 0(a2)
+ beqz v0, 0f
+/*
+ * If we have a queue, provoke dispatch within the VPE by setting C_SW1
+ */
+ mfc0 v0, CP0_CAUSE
+ ori v0, v0, C_SW1
+ mtc0 v0, CP0_CAUSE
+0:
+ /*
+ * This test should really never branch but
+ * let's be prudent here. Having atomized
+ * the shared register modifications, we can
+ * now EVPE, and must do so before interrupts
+ * are potentially re-enabled.
+ */
+ andi a1, a1, MVPCONTROL_EVP
beqz a1, 1f
- emt
+ evpe
1:
+ /* We know that TCStatua.IXMT should be set from above */
+ xori a0, a0, TCSTATUS_IXMT
+ or a0, a0, v1
+ mtc0 a0, CP0_TCSTATUS
+ _ehb
+
.set mips0
#endif /* CONFIG_MIPS_MT_SMTC */
LONG_L v1, PT_EPC(sp)
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