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powerpc/pseries: Machine check use rtas_call_unlocked() with args on stack

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With the previous patch, machine checks can use rtas_call_unlocked()
which avoids the RTAS spinlock which would deadlock if a machine
check hits while making an RTAS call.

This also avoids the complex RTAS error logging which has more RTAS
calls and includes kmalloc (which can return memory beyond RMA, which
would also crash).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200508043408.886394-11-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2020-05-08 14:34:02 +10:00 committed by Michael Ellerman
parent d2cbbd45d4
commit 2576f5f916
1 changed files with 9 additions and 1 deletions
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10
arch/powerpc/platforms/pseries/ras.c
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@ -468,7 +468,15 @@ static struct rtas_error_log *fwnmi_get_errinfo(struct pt_regs *regs)
*/
static void fwnmi_release_errinfo(void)
{
int ret = rtas_call(ibm_nmi_interlock_token, 0, 1, NULL);
struct rtas_args rtas_args;
int ret;
/*
* On pseries, the machine check stack is limited to under 4GB, so
* args can be on-stack.
*/
rtas_call_unlocked(&rtas_args, ibm_nmi_interlock_token, 0, 1, NULL);
ret = be32_to_cpu(rtas_args.rets[0]);
if (ret != 0)
printk(KERN_ERR "FWNMI: nmi-interlock failed: %d\n", ret);
}