Excerpts from Fabiano Rosas's message of July 27, 2021 6:17 am:
> If the nested hypervisor has no access to a facility because it has
> been disabled by the host, it should also not be able to see the
> Hypervisor Facility Unavailable that arises from one of its guests
> trying to access the facility.
>
> This patch turns a HFU that happened in L2 into a Hypervisor Emulation
> Assistance interrupt and forwards it to L1 for handling. The ones that
> happened because L1 explicitly disabled the facility for L2 are still
> let through, along with the corresponding Cause bits in the HFSCR.
>
> Signed-off-by: Fabiano Rosas <faro...@linux.ibm.com>
> Reviewed-by: Nicholas Piggin <npig...@gmail.com>
> ---
> arch/powerpc/kvm/book3s_hv_nested.c | 32 +++++++++++++++++++++++------
> 1 file changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c
> b/arch/powerpc/kvm/book3s_hv_nested.c
> index 8215dbd4be9a..d544b092b49a 100644
> --- a/arch/powerpc/kvm/book3s_hv_nested.c
> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> @@ -99,7 +99,7 @@ static void byteswap_hv_regs(struct hv_guest_state *hr)
> hr->dawrx1 = swab64(hr->dawrx1);
> }
>
> -static void save_hv_return_state(struct kvm_vcpu *vcpu, int trap,
> +static void save_hv_return_state(struct kvm_vcpu *vcpu,
> struct hv_guest_state *hr)
> {
> struct kvmppc_vcore *vc = vcpu->arch.vcore;
> @@ -118,7 +118,7 @@ static void save_hv_return_state(struct kvm_vcpu *vcpu,
> int trap,
> hr->pidr = vcpu->arch.pid;
> hr->cfar = vcpu->arch.cfar;
> hr->ppr = vcpu->arch.ppr;
> - switch (trap) {
> + switch (vcpu->arch.trap) {
> case BOOK3S_INTERRUPT_H_DATA_STORAGE:
> hr->hdar = vcpu->arch.fault_dar;
> hr->hdsisr = vcpu->arch.fault_dsisr;
> @@ -128,9 +128,29 @@ static void save_hv_return_state(struct kvm_vcpu *vcpu,
> int trap,
> hr->asdr = vcpu->arch.fault_gpa;
> break;
> case BOOK3S_INTERRUPT_H_FAC_UNAVAIL:
> - hr->hfscr = ((~HFSCR_INTR_CAUSE & hr->hfscr) |
> - (HFSCR_INTR_CAUSE & vcpu->arch.hfscr));
> - break;
> + {
> + u8 cause = vcpu->arch.hfscr >> 56;
Can this be u64 just to help gcc?
> +
> + WARN_ON_ONCE(cause >= BITS_PER_LONG);
> +
> + if (!(hr->hfscr & (1UL << cause))) {
> + hr->hfscr = ((~HFSCR_INTR_CAUSE & hr->hfscr) |
> + (HFSCR_INTR_CAUSE & vcpu->arch.hfscr));
> + break;
> + }
> +
> + /*
> + * We have disabled this facility, so it does not
> + * exist from L1's perspective. Turn it into a HEAI.
> + */
> + vcpu->arch.trap = BOOK3S_INTERRUPT_H_EMUL_ASSIST;
> + kvmppc_load_last_inst(vcpu, INST_GENERIC,
> &vcpu->arch.emul_inst);
Hmm, this doesn't handle kvmpc_load_last_inst failure. Other code tends
to just resume guest and retry in this case. Can we do that here?
> +
> + /* Don't leak the cause field */
> + hr->hfscr &= ~HFSCR_INTR_CAUSE;
This hunk also remains -- shouldn't change HFSCR for HEA, only HFAC.
Thanks,
Nick
