From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keith Owens <kaos@sgi.com>
Date: Mon, 09 Feb 2004 01:53:28 +0000
Subject: mca.c: Incorrect recovery from TLB errors?
Message-Id: <2848.1076291608@kao2.melbourne.sgi.com>
List-Id: <linux-ia64.vger.kernel.org>
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To: linux-ia64@vger.kernel.org

In both 2.4 and 2.6 kernels, arch/ia64/kernel/mca.c
ia64_return_to_sal_check() has

	if (psp->cc = 1 && psp->bc = 1 && psp->rc = 1 && psp->uc = 1)
		ia64_os_to_sal_handoff_state.imots_os_status = IA64_MCA_COLD_BOOT;
	else
		ia64_os_to_sal_handoff_state.imots_os_status = IA64_MCA_CORRECTED;

Why does it test for all the cc/bc/rc/uc bits being set?  Surely that
should be or, not and?  The real test for recovery is

	psp->tc && !(psp->cc || psp->bc || psp->rc || psp->uc)

The existing code is also inconsistent with the test in mca_asm.S, that
only tests for psp->tc being 1 and ignores the other bits.

Tony: it makes life easier for kdb if the "am I going to recover" test
is promoted from ia64_return_to_sal_check() to ia64_mca_ucmc_handler()
and passed down to ia64_return_to_sal_check().  Otherwise kdb has to
duplicate the code in ia64_return_to_sal_check() to decide if the MCA
is recoverable or not, normally you do not want kdb to handle a
recovered error.  Any objections to this?

void
ia64_mca_ucmc_handler(void)
{
	pal_processor_state_info_t *psp = (pal_processor_state_info_t *)
		&ia64_sal_to_os_handoff_state.proc_state_param;
	int recover = psp->tc && !(psp->cc || psp->bc || psp->rc || psp->uc);
	...
	ia64_return_to_sal_check(psp, recover)
}