Commit 070e76cb authored Nov 27, 2014 by Leonid Yegoshin Committed by Ralf Baechle Nov 27, 2014

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>

parent b4da18b3

arch/mips/mm/tlbex.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

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