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MIPS: HTW: Prevent accidental HTW start due to nested htw_{start, stop}

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activate_mm() and switch_mm() call get_new_mmu_context() which in turn
can enable the HTW before the entryhi is changed with the new ASID.
Since the latter will enable the HTW in local_flush_tlb_all(),
then there is a small timing window where the HTW is running with the
new ASID but with an old pgd since the TLBMISS_HANDLER_SETUP_PGD
hasn't assigned a new one yet. In order to prevent that, we introduce a
simple htw counter to avoid starting HTW accidentally due to nested
htw_{start,stop}() sequences. Moreover, since various IPI calls can
enforce TLB flushing operations on a different core, such an operation
may interrupt another htw_{stop,start} in progress leading inconsistent
updates of the htw_seq variable. In order to avoid that, we disable the
interrupts whenever we update that variable.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: <stable@vger.kernel.org> # 3.17+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9118/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Markos Chandras
2015-01-26 13:04:33 +00:00
committed by Ralf Baechle
parent fde3538a8a
commit ed4cbc81ad
4 changed files with 32 additions and 8 deletions
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24
arch/mips/include/asm/pgtable.h
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@@ -99,19 +99,31 @@ extern void paging_init(void);
#define htw_stop() \
do { \
unsigned long flags; \
\
if (cpu_has_htw) { \
write_c0_pwctl(read_c0_pwctl() & \
~(1 << MIPS_PWCTL_PWEN_SHIFT)); \
back_to_back_c0_hazard(); \
local_irq_save(flags); \
if(!raw_current_cpu_data.htw_seq++) { \
write_c0_pwctl(read_c0_pwctl() & \
~(1 << MIPS_PWCTL_PWEN_SHIFT)); \
back_to_back_c0_hazard(); \
} \
local_irq_restore(flags); \
} \
} while(0)
#define htw_start() \
do { \
unsigned long flags; \
\
if (cpu_has_htw) { \
write_c0_pwctl(read_c0_pwctl() | \
(1 << MIPS_PWCTL_PWEN_SHIFT)); \
back_to_back_c0_hazard(); \
local_irq_save(flags); \
if (!--raw_current_cpu_data.htw_seq) { \
write_c0_pwctl(read_c0_pwctl() | \
(1 << MIPS_PWCTL_PWEN_SHIFT)); \
back_to_back_c0_hazard(); \
} \
local_irq_restore(flags); \
} \
} while(0)