From 070e76cb3ffe43f6855492e77c96680c562598f0 Mon Sep 17 00:00:00 2001 From: Leonid Yegoshin Date: Thu, 27 Nov 2014 11:13:08 +0000 Subject: [PATCH] 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 Signed-off-by: Markos Chandras Reviewed-by: James Hogan Cc: # v3.17+ Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/8599/ Signed-off-by: Ralf Baechle --- arch/mips/mm/tlbex.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) 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; } -- 2.20.1