Re: [PATCH] KVM: PPC: Book3S HV: Fix r3 corruption in h_set_dabr()

quoted

quoted

3:
        /* Emulate H_SET_DABR/X on P8 for the sake of compat mode
guests */
        rlwimi  r5, r4, 5, DAWRX_DR | DAWRX_DW
c00000000010b03c:       74 2e 85 50     rlwimi  r5,r4,5,25,26
        rlwimi  r5, r4, 2, DAWRX_WT
c00000000010b040:       f6 16 85 50     rlwimi  r5,r4,2,27,27
        clrrdi  r4, r4, 3
c00000000010b044:       24 07 84 78     rldicr  r4,r4,0,60
        std     r4, VCPU_DAWR(r3)
c00000000010b048:       c0 13 83 f8     std     r4,5056(r3)
        std     r5, VCPU_DAWRX(r3)
c00000000010b04c:       c8 13 a3 f8     std     r5,5064(r3)
        mtspr   SPRN_DAWR, r4
c00000000010b050:       a6 2b 94 7c     mtspr   180,r4
        mtspr   SPRN_DAWRX, r5
c00000000010b054:       a6 2b bc 7c     mtspr   188,r5
        li      r3, 0
c00000000010b058:       00 00 60 38     li      r3,0
        blr
c00000000010b05c:       20 00 80 4e     blr

It's the `mtspr   SPRN_DAWR, r4` as you're HV=0.  I'm not sure how
nested works
in that regard. Is the level above suppose to trap and emulate
that?  

Yeah so as a nested hypervisor we need to avoid that call to mtspr
SPRN_DAWR since it's HV privileged and we run with HV = 0.

The fix will be to check kvmhv_on_pseries() before doing the write. In
fact we should avoid the write any time we call the function from _not_
real mode.

I'll submit a fix for the KVM side. Doesn't look like this is anything
to do with Mikey's patch, was always broken as far as I can tell.

Thanks Suraj.

Mikey