Date: Wed, 01 Jul 2009 08:39:00 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: neelnatu@yahoo.com Cc: freebsd-mips@freebsd.org Subject: Re: Machine Check exception during bootup Message-ID: <20090701.083900.1346819654.imp@bsdimp.com> In-Reply-To: <14584.70267.qm@web34403.mail.mud.yahoo.com> References: <14584.70267.qm@web34403.mail.mud.yahoo.com>
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In message: <14584.70267.qm@web34403.mail.mud.yahoo.com>
Neelkanth Natu <neelnatu@yahoo.com> writes:
: r02.eng.netapp.com/vol/home24/neelnatu/p4/freebsd_sibyte/src/sys/mips/mips/tlb.S ====
: @@ -81,14 +81,14 @@
: #define _MFC0 dmfc0
: #define _MTC0 dmtc0
: #define WIRED_SHIFT 34
: -#define PAGE_SHIFT 34
: +#define PAGE_SHIFT 12
: #else
: #define _SLL sll
: #define _SRL srl
: #define _MFC0 mfc0
: #define _MTC0 mtc0
: #define WIRED_SHIFT 2
: -#define PAGE_SHIFT 2
: +#define PAGE_SHIFT 12
: #endif
These are wrong. PAGE_SHIFT is supposed to be the bit position in the
TLB, not the size of the page for multiplication. At least in thoery,
but looking at the manual doesn't even bear that out...
However, it appears it isn't used that way at all in the rest of the
code. This means we should move it outside of the #ifdef, since it
has nothing to do with ISA we're compiling for.
: .set noreorder # Noreorder is default style!
: #if defined(ISA_MIPS32)
: @@ -232,22 +232,30 @@
: mtc0 zero, COP_0_STATUS_REG # Disable interrupts
: ITLBNOPFIX
: mfc0 t1, COP_0_TLB_WIRED
: - li v0, MIPS_KSEG3_START + 0x0fff0000 # invalid address
: _MFC0 t0, COP_0_TLB_HI # Save the PID
:
: - _MTC0 v0, COP_0_TLB_HI # Mark entry high as invalid
: _MTC0 zero, COP_0_TLB_LO0 # Zero out low entry0.
: _MTC0 zero, COP_0_TLB_LO1 # Zero out low entry1.
: mtc0 zero, COP_0_TLB_PG_MASK # Zero out mask entry.
: +
: + #
: + # Load invalid entry, each TLB entry should have it's own bogus
: + # address calculated by following expression:
: + # MIPS_KSEG0_START + 0x0fff0000 + 2 * i * PAGE_SIZE;
: + # One bogus value for every TLB entry might cause MCHECK exception
: + #
: + sll t3, t1, PAGE_SHIFT + 1
: + li v0, MIPS_KSEG0_START + 0x0fff0000 # invalid address
: + addu v0, t3
I'll note that NetBSD doesn't add the 0x0fff0000 on the end here. I
don't understand why we do it, even though I likely added this to the
port. Does it work without it?
Warner
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