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MIPS: mm: tlb-r4k: Uniquify TLB entries on init

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Hardware or bootloader will initialize TLB entries to any value, which
may collide with kernel's UNIQUE_ENTRYHI value. On MIPS microAptiv/M5150
family of cores this will trigger machine check exception and cause boot
failure. On M5150 simulation this could happen 7 times out of 1000 boots.

Replace local_flush_tlb_all() with r4k_tlb_uniquify() which probes each
TLB ENTRIHI unique value for collisions before it's written, and in case
of collision try a different ASID.

Cc: stable@kernel.org
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
This commit is contained in:
Jiaxun Yang
2025-06-07 13:43:56 +01:00
committed by Thomas Bogendoerfer
parent b9ace0647f
commit 35ad7e1815
1 changed files with 55 additions and 1 deletions
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56
arch/mips/mm/tlb-r4k.c
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@@ -508,6 +508,60 @@ static int __init set_ntlb(char *str)
__setup("ntlb=", set_ntlb);
/* Initialise all TLB entries with unique values */
static void r4k_tlb_uniquify(void)
{
int entry = num_wired_entries();
htw_stop();
write_c0_entrylo0(0);
write_c0_entrylo1(0);
while (entry < current_cpu_data.tlbsize) {
unsigned long asid_mask = cpu_asid_mask(&current_cpu_data);
unsigned long asid = 0;
int idx;
/* Skip wired MMID to make ginvt_mmid work */
if (cpu_has_mmid)
asid = MMID_KERNEL_WIRED + 1;
/* Check for match before using UNIQUE_ENTRYHI */
do {
if (cpu_has_mmid) {
write_c0_memorymapid(asid);
write_c0_entryhi(UNIQUE_ENTRYHI(entry));
} else {
write_c0_entryhi(UNIQUE_ENTRYHI(entry) | asid);
}
mtc0_tlbw_hazard();
tlb_probe();
tlb_probe_hazard();
idx = read_c0_index();
/* No match or match is on current entry */
if (idx < 0 || idx == entry)
break;
/*
* If we hit a match, we need to try again with
* a different ASID.
*/
asid++;
} while (asid < asid_mask);
if (idx >= 0 && idx != entry)
panic("Unable to uniquify TLB entry %d", idx);
write_c0_index(entry);
mtc0_tlbw_hazard();
tlb_write_indexed();
entry++;
}
tlbw_use_hazard();
htw_start();
flush_micro_tlb();
}
/*
* Configure TLB (for init or after a CPU has been powered off).
*/
@@ -547,7 +601,7 @@ static void r4k_tlb_configure(void)
temp_tlb_entry = current_cpu_data.tlbsize - 1;
/* From this point on the ARC firmware is dead. */
local_flush_tlb_all();
r4k_tlb_uniquify();
/* Did I tell you that ARC SUCKS? */
}