970/PowerMac G5 cpudep_ap_bootstrap slb-related hangup *solved* . . .

[Mark Millard]

[This continues a prior message, but I choose a new subject
text for the testing that showed the kind of material working.]

I have the slbtrap/handle_kernel_slb_spill working instead
of hanging up when it has an slb-miss (and well as when there
is no miss).

In /usr/src/sys/powerpc/aim/mp_cpudep.c I moved the
970 code for HID0 and HID1 from cpudep_ap_setup, code
that looks like,

                /* Set HIOR to 0 */
                __asm __volatile("mtspr 311,%0" :: "r"(0));
                powerpc_sync();

                /*
                 * The 970 has strange rules about how to update HID registers.
                 * See Table 2-3, 970MP manual
                 *
                 * Note: HID4 and HID5 restored already in
                 * cpudep_ap_early_bootstrap()
                 */

                __asm __volatile("mtasr %0; sync" :: "r"(0));
        #ifdef __powerpc64__
                __asm __volatile(" \
                        sync; isync;                                    \
                        mtspr   %1, %0;                                 \
                        mfspr   %0, %1; mfspr   %0, %1; mfspr   %0, %1; \
                        mfspr   %0, %1; mfspr   %0, %1; mfspr   %0, %1; \
                        sync; isync"
                    :: "r"(bsp_state[0]), "K"(SPR_HID0));
                __asm __volatile("sync; isync;  \
                    mtspr %1, %0; mtspr %1, %0; sync; isync"
                    :: "r"(bsp_state[1]), "K"(SPR_HID1));
        #else
                __asm __volatile(" \
                        ld      %0,0(%2);                               \
                        sync; isync;                                    \
                        mtspr   %1, %0;                                 \
                        mfspr   %0, %1; mfspr   %0, %1; mfspr   %0, %1; \
                        mfspr   %0, %1; mfspr   %0, %1; mfspr   %0, %1; \
                        sync; isync"
                    : "=r"(reg) : "K"(SPR_HID0), "b"(bsp_state));
                __asm __volatile("ld %0, 8(%2); sync; isync;    \
                    mtspr %1, %0; mtspr %1, %0; sync; isync"
                    : "=r"(reg) : "K"(SPR_HID1), "b"(bsp_state));
        #endif

                powerpc_sync();

Here to? moved it to cpudep_ap_early_bootstrap, just before the
code for HID4 and HID5, and I commented out 2 #if/endif lines:

void
cpudep_ap_early_bootstrap(void)
{
//#ifndef __powerpc64__
        register_t reg;
//#endif

        switch (mfpvr() >> 16) {
        case IBM970:
        case IBM970FX:
        case IBM970MP:
>.>.> INSERT CODE HERE <.<.<.

                /* Restore HID4 and HID5, which are necessary for the MMU */
                        
#ifdef __powerpc64__
                mtspr(SPR_HID4, bsp_state[2]); powerpc_sync(); isync();
                mtspr(SPR_HID5, bsp_state[3]); powerpc_sync(); isync();
#else
                __asm __volatile("ld %0, 16(%2); sync; isync;   \
                    mtspr %1, %0; sync; isync;"
                    : "=r"(reg) : "K"(SPR_HID4), "b"(bsp_state));
                __asm __volatile("ld %0, 24(%2); sync; isync;   \
                    mtspr %1, %0; sync; isync;"
                    : "=r"(reg) : "K"(SPR_HID5), "b"(bsp_state));
#endif
                powerpc_sync();
                break;
. . .

This does the initialization before cpudep_ap_bootstrap,
instead of after.

With things then sufficiently initialized for PSL_IR|PSL_DR
code to doing things like pcpup->pc_curthread->td_pcb->
that sometimes have slb misses, it boots fine,
loading into the slb as needed. No more checkstop status
(or whatever it was).

I do not know if non-970 contexts should have similar
changes in the ordering of initializations or not.
But, clearly, the 970 family members do need such.

I'm not claiming that other material from other notes
that I sent out should be ignored, only that the above
changes the observed failing behavior, and so is a big
gain all by itself. And it is simple to do without
other investigations that might be involved in the
more overall context.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)