Quoting Qian Cai <q...@redhat.com>:
On Thu, 2020-12-03 at 12:17 -0500, Qian Cai wrote:
[]
> +static inline bool
> +bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool
is_write)
> +{
> + return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
> + (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE :
AMR_KUAP_BLOCK_READ)),
> + "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
> +}
A simple "echo t > /proc/sysrq-trigger" will trigger this warning almost
endlessly on POWER9 NV.
I have just realized the patch just moved this warning around, so
the issue was
pre-existent. Since I have not tested sysrq-t regularly, I am not
sure when it
started to break. So far, I have reverted some of those for testing which did
not help, i.e., the sysrq-t issue remains.
16852975f0f Revert "powerpc/64s: Use early_mmu_has_feature() in set_kuap()"
129e240ead32 Revert "powerpc: Implement user_access_save() and
user_access_restore()"
edb0046c842c Revert "powerpc/64s/kuap: Add missing isync to KUAP
restore paths"
2d46ee87ce44 Revert "powerpc/64/kuap: Conditionally restore AMR in
interrupt exit"
c1e0e805fc57 Revert "powerpc/64s/kuap: Conditionally restore AMR in
kuap_restore_amr asm"
7f30b7aaf23a Revert "selftests/powerpc: rfi_flush: disable entry
flush if present"
bc9b9967a100 Revert "powerpc/64s: flush L1D on kernel entry"
b77e7b54f5eb Revert "powerpc/64s: flush L1D after user accesses"
22dddf532c64 Revert "powerpc: Only include kup-radix.h for 64-bit Book3S"
2679d155c46a Revert "selftests/powerpc: entry flush test"
87954b9b4243 Revert "selftests/powerpc: refactor entry and rfi_flush tests"
342d82bd4c5d Revert "powerpc/64s: rename pnv|pseries_setup_rfi_flush
to _setup_security_mitigations"
I also hit that WARNING in the same way earlier this week.
I think it has been broken by commit c33165253492 ("powerpc: use
non-set_fs based maccess routines")
IIUC we should provide copy_from_kernel_nofault_allowed() to avoid that.
Christophe
