powerpc/mce: Avoid nmi_enter/exit in real mode on pseries hash

Use of nmi_enter/exit in real mode handler causes the kernel to panic
and reboot on injecting SLB mutihit on pseries machine running in hash
MMU mode, because these calls try to accesses memory outside RMO
region in real mode handler where translation is disabled.

Add check to not to use these calls on pseries machine running in hash
MMU mode.

Fixes: 116ac378bb3f ("powerpc/64s: machine check interrupt update NMI accounting")
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201009064005.19777-2-ganeshgr@linux.ibm.com

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index ada59f6c4298f496ad9e44d0096112e1206ac151..63702c0badb973651d5629f15a72d8eec10fcc13 100644 (file)
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -591,12 +591,11 @@ EXPORT_SYMBOL_GPL(machine_check_print_event_info);
 long notrace machine_check_early(struct pt_regs *regs)
 {
        long handled = 0;
-       bool nested = in_nmi();
        u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
 
        this_cpu_set_ftrace_enabled(0);
-
-       if (!nested)
+       /* Do not use nmi_enter/exit for pseries hpte guest */
+       if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
                nmi_enter();
 
        hv_nmi_check_nonrecoverable(regs);
@@ -607,7 +606,7 @@ long notrace machine_check_early(struct pt_regs *regs)
        if (ppc_md.machine_check_early)
                handled = ppc_md.machine_check_early(regs);
 
-       if (!nested)
+       if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
                nmi_exit();
 
        this_cpu_set_ftrace_enabled(ftrace_enabled);