4.4-stable review patch. If anyone has any objections, please let me know.
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From: Mahesh Salgaonkar mahesh@linux.vnet.ibm.com
commit cd813e1cd7122f2c261dce5b54d1e0c97f80e1a5 upstream.
During Machine Check interrupt on pseries platform, register r3 points RTAS extended event log passed by hypervisor. Since hypervisor uses r3 to pass pointer to rtas log, it stores the original r3 value at the start of the memory (first 8 bytes) pointed by r3. Since hypervisor stores this info and rtas log is in BE format, linux should make sure to restore r3 value in correct endian format.
Without this patch when MCE handler, after recovery, returns to code that that caused the MCE may end up with Data SLB access interrupt for invalid address followed by kernel panic or hang.
Severe Machine check interrupt [Recovered] NIP [d00000000ca301b8]: init_module+0x1b8/0x338 [bork_kernel] Initiator: CPU Error type: SLB [Multihit] Effective address: d00000000ca70000 cpu 0xa: Vector: 380 (Data SLB Access) at [c0000000fc7775b0] pc: c0000000009694c0: vsnprintf+0x80/0x480 lr: c0000000009698e0: vscnprintf+0x20/0x60 sp: c0000000fc777830 msr: 8000000002009033 dar: a803a30c000000d0 current = 0xc00000000bc9ef00 paca = 0xc00000001eca5c00 softe: 3 irq_happened: 0x01 pid = 8860, comm = insmod vscnprintf+0x20/0x60 vprintk_emit+0xb4/0x4b0 vprintk_func+0x5c/0xd0 printk+0x38/0x4c init_module+0x1c0/0x338 [bork_kernel] do_one_initcall+0x54/0x230 do_init_module+0x8c/0x248 load_module+0x12b8/0x15b0 sys_finit_module+0xa8/0x110 system_call+0x58/0x6c --- Exception: c00 (System Call) at 00007fff8bda0644 SP (7fffdfbfe980) is in userspace
This patch fixes this issue.
Fixes: a08a53ea4c97 ("powerpc/le: Enable RTAS events support") Cc: stable@vger.kernel.org # v3.15+ Reviewed-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Mahesh Salgaonkar mahesh@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/platforms/pseries/ras.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/platforms/pseries/ras.c +++ b/arch/powerpc/platforms/pseries/ras.c @@ -300,7 +300,7 @@ static struct rtas_error_log *fwnmi_get_ }
savep = __va(regs->gpr[3]); - regs->gpr[3] = savep[0]; /* restore original r3 */ + regs->gpr[3] = be64_to_cpu(savep[0]); /* restore original r3 */
/* If it isn't an extended log we can use the per cpu 64bit buffer */ h = (struct rtas_error_log *)&savep[1];