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Revert "KVM: PPC: Book3S HV Nested: Stop forwarding all HFUs to L1"

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This reverts commit 7c3ded5735.

On PowerNV, when a nested guest tries to use a feature prohibited by
HFSCR, the nested hypervisor (L1) should get a H_FAC_UNAVAILABLE trap
so that L1 can emulate the feature. But with the change introduced by
commit 7c3ded5735 ("KVM: PPC: Book3S HV Nested: Stop forwarding all HFUs
to L1") the L1 ends up getting a H_EMUL_ASSIST because of which, the L1
ends up injecting a SIGILL when L2 (nested guest) tries to use doorbells.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241109063301.105289-2-gautam@linux.ibm.com
This commit is contained in:
Gautam Menghani 2024-11-09 12:02:55 +05:30 committed by Michael Ellerman
parent 96e266e3bc
commit ed351c5743
1 changed files with 2 additions and 29 deletions
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31
arch/powerpc/kvm/book3s_hv.c
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@ -2063,36 +2063,9 @@ static int kvmppc_handle_nested_exit(struct kvm_vcpu *vcpu)
fallthrough; /* go to facility unavailable handler */
#endif
case BOOK3S_INTERRUPT_H_FAC_UNAVAIL: {
u64 cause = vcpu->arch.hfscr >> 56;
/*
* Only pass HFU interrupts to the L1 if the facility is
* permitted but disabled by the L1's HFSCR, otherwise
* the interrupt does not make sense to the L1 so turn
* it into a HEAI.
*/
if (!(vcpu->arch.hfscr_permitted & (1UL << cause)) ||
(vcpu->arch.nested_hfscr & (1UL << cause))) {
ppc_inst_t pinst;
vcpu->arch.trap = BOOK3S_INTERRUPT_H_EMUL_ASSIST;
/*
* If the fetch failed, return to guest and
* try executing it again.
*/
r = kvmppc_get_last_inst(vcpu, INST_GENERIC, &pinst);
vcpu->arch.emul_inst = ppc_inst_val(pinst);
if (r != EMULATE_DONE)
r = RESUME_GUEST;
else
r = RESUME_HOST;
} else {
r = RESUME_HOST;
}
case BOOK3S_INTERRUPT_H_FAC_UNAVAIL:
r = RESUME_HOST;
break;
}
case BOOK3S_INTERRUPT_HV_RM_HARD:
vcpu->arch.trap = 0;