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authorLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>2014-11-27 11:13:08 +0000
committerRalf Baechle <ralf@linux-mips.org>2014-11-27 17:21:56 +0100
commit070e76cb3ffe43f6855492e77c96680c562598f0 (patch)
treea873e8a0d4424ab18274d7b6ecc32537f5f8cccc
parentb4da18b3714a35c1123522810cc5ec0cd2ee4101 (diff)
downloadkernel-070e76cb3ffe43f6855492e77c96680c562598f0.tar.gz
MIPS: tlbex: Fix potential HTW race on TLBL/M/S handlers
There is a potential race when probing the TLB in TLBL/M/S exception handlers for a matching entry. Between the time we hit a TLBL/S/M exception and the time we get to execute the TLBP instruction, the HTW may have replaced the TLB entry we are interested in hence the TLB probe may fail. However, in the existing handlers, we never checked the status of the TLBP (ie check the result in the C0/Index register). We fix this by adding such a check when the core implements the HTW. If we couldn't find a matching entry, we return back and try again. Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com> Signed-off-by: Markos Chandras <markos.chandras@imgtec.com> Reviewed-by: James Hogan <james.hogan@imgtec.com> Cc: <stable@vger.kernel.org> # v3.17+ Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/8599/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
-rw-r--r--arch/mips/mm/tlbex.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index b5f228e7eae6..e3328a96e809 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -1872,8 +1872,16 @@ build_r4000_tlbchange_handler_head(u32 **p, struct uasm_label **l,
uasm_l_smp_pgtable_change(l, *p);
#endif
iPTE_LW(p, wr.r1, wr.r2); /* get even pte */
- if (!m4kc_tlbp_war())
+ if (!m4kc_tlbp_war()) {
build_tlb_probe_entry(p);
+ if (cpu_has_htw) {
+ /* race condition happens, leaving */
+ uasm_i_ehb(p);
+ uasm_i_mfc0(p, wr.r3, C0_INDEX);
+ uasm_il_bltz(p, r, wr.r3, label_leave);
+ uasm_i_nop(p);
+ }
+ }
return wr;
}