Nicholas Piggin <npig...@gmail.com> writes:
> KVM PR does not implement address translation modes on interrupt, so it
> must not allow H_SET_MODE to succeed. The behaviour change caused by
> this mode is architected and not advisory (interrupts *must* behave
> differently).
>
> QEMU does not deal with differences in AIL support in the host. The
> solution to that is a spapr capability and corresponding KVM CAP, but
> this patch does not break things more than before (the host behaviour
> already differs, this change just disallows some modes that are not
> implemented properly).
>
> By happy coincidence, this allows PR Linux guests that are using the SCV
> facility to boot and run, because Linux disables the use of SCV if AIL
> can not be set to 3. This does not fix the underlying problem of missing
> SCV support (an OS could implement real-mode SCV vectors and try to
> enable the facility). The true fix for that is for KVM PR to emulate scv
> interrupts from the facility unavailable interrupt.
>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
Reviewed-by: Fabiano Rosas <faro...@linux.ibm.com>
> ---
> arch/powerpc/kvm/book3s_pr_papr.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/arch/powerpc/kvm/book3s_pr_papr.c
> b/arch/powerpc/kvm/book3s_pr_papr.c
> index 1f10e7dfcdd0..dc4f51ac84bc 100644
> --- a/arch/powerpc/kvm/book3s_pr_papr.c
> +++ b/arch/powerpc/kvm/book3s_pr_papr.c
> @@ -281,6 +281,22 @@ static int kvmppc_h_pr_logical_ci_store(struct kvm_vcpu
> *vcpu)
> return EMULATE_DONE;
> }
>
> +static int kvmppc_h_pr_set_mode(struct kvm_vcpu *vcpu)
> +{
> + unsigned long mflags = kvmppc_get_gpr(vcpu, 4);
> + unsigned long resource = kvmppc_get_gpr(vcpu, 5);
> +
> + if (resource == H_SET_MODE_RESOURCE_ADDR_TRANS_MODE) {
> + /* KVM PR does not provide AIL!=0 to guests */
> + if (mflags == 0)
> + kvmppc_set_gpr(vcpu, 3, H_SUCCESS);
> + else
> + kvmppc_set_gpr(vcpu, 3, H_UNSUPPORTED_FLAG_START - 63);
> + return EMULATE_DONE;
> + }
> + return EMULATE_FAIL;
> +}
> +
> #ifdef CONFIG_SPAPR_TCE_IOMMU
> static int kvmppc_h_pr_put_tce(struct kvm_vcpu *vcpu)
> {
> @@ -384,6 +400,8 @@ int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
> return kvmppc_h_pr_logical_ci_load(vcpu);
> case H_LOGICAL_CI_STORE:
> return kvmppc_h_pr_logical_ci_store(vcpu);
> + case H_SET_MODE:
> + return kvmppc_h_pr_set_mode(vcpu);
> case H_XIRR:
> case H_CPPR:
> case H_EOI:
> @@ -421,6 +439,7 @@ int kvmppc_hcall_impl_pr(unsigned long cmd)
> case H_CEDE:
> case H_LOGICAL_CI_LOAD:
> case H_LOGICAL_CI_STORE:
> + case H_SET_MODE:
> #ifdef CONFIG_KVM_XICS
> case H_XIRR:
> case H_CPPR:
> @@ -447,6 +466,7 @@ static unsigned int default_hcall_list[] = {
> H_BULK_REMOVE,
> H_PUT_TCE,
> H_CEDE,
> + H_SET_MODE,
> #ifdef CONFIG_KVM_XICS
> H_XIRR,
> H_CPPR,
