Commit d2bb01b0 authored by Kevin D. Kissell's avatar Kevin D. Kissell Committed by Ralf Baechle

[MIPS] SMTC: Close tiny holes in the SMTC IPI replay system.

Signed-off-by: default avatarKevin D. Kissell <kevink@paralogos.com>
Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 9cc12363
......@@ -79,11 +79,6 @@ FEXPORT(syscall_exit)
FEXPORT(restore_all) # restore full frame
#ifdef CONFIG_MIPS_MT_SMTC
/* Detect and execute deferred IPI "interrupts" */
LONG_L s0, TI_REGS($28)
LONG_S sp, TI_REGS($28)
jal deferred_smtc_ipi
LONG_S s0, TI_REGS($28)
#ifdef CONFIG_MIPS_MT_SMTC_IM_BACKSTOP
/* Re-arm any temporarily masked interrupts not explicitly "acked" */
mfc0 v0, CP0_TCSTATUS
......@@ -112,6 +107,11 @@ FEXPORT(restore_all) # restore full frame
xor t0, t0, t3
mtc0 t0, CP0_TCCONTEXT
#endif /* CONFIG_MIPS_MT_SMTC_IM_BACKSTOP */
/* Detect and execute deferred IPI "interrupts" */
LONG_L s0, TI_REGS($28)
LONG_S sp, TI_REGS($28)
jal deferred_smtc_ipi
LONG_S s0, TI_REGS($28)
#endif /* CONFIG_MIPS_MT_SMTC */
.set noat
RESTORE_TEMP
......
......@@ -70,7 +70,7 @@ static atomic_t ipi_timer_latch[NR_CPUS];
#define IPIBUF_PER_CPU 4
static struct smtc_ipi_q IPIQ[NR_CPUS];
struct smtc_ipi_q IPIQ[NR_CPUS];
static struct smtc_ipi_q freeIPIq;
......
......@@ -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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