spapr/target-ppc/kvm: Only add hcall-instructions if KVM supports it
ePAPR defines "hcall-instructions" device-tree property which contains code to call hypercalls in ePAPR paravirtualized guests. In general pseries guests won't use this property, instead using the PAPR defined hypercall interface. However, this property has been re-used to implement a hack to allow PR KVM to run (slightly modified) guests in some situations where it otherwise wouldn't be able to (because the system's L0 hypervisor doesn't forward the PAPR hypercalls to the PR KVM kernel). Hence, this property is always present in the device tree for pseries guests. All KVM guests use it at least to read features via the KVM_HC_FEATURES hypercall. The property is populated by the code returned from the KVM's KVM_PPC_GET_PVINFO ioctl; if not implemented in the KVM, QEMU supplies code which will fail all hypercall attempts. If QEMU does not create the property, and the guest kernel is compiled with CONFIG_EPAPR_PARAVIRT (which is normally the case), there is exactly the same stub at @epapr_hypercall_start already. Rather than maintaining this fairly useless stub implementation, it makes more sense not to create the property in the device tree in the first place if the host kernel does not implement it. This changes kvmppc_get_hypercall() to return 1 if the host kernel does not implement KVM_CAP_PPC_GET_PVINFO. The caller can use it to decide on whether to create the property or not. This changes the pseries machine to not create the property if KVM does not implement KVM_PPC_GET_PVINFO. In practice this means that from now on the property will not be created if either HV KVM or TCG is used. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> [reworded commit message for clarity --dwg] Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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@ -497,11 +497,12 @@ static void *spapr_create_fdt_skel(hwaddr initrd_base,
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* Older KVM versions with older guest kernels were broken with the
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* magic page, don't allow the guest to map it.
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*/
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kvmppc_get_hypercall(first_cpu->env_ptr, hypercall,
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sizeof(hypercall));
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if (!kvmppc_get_hypercall(first_cpu->env_ptr, hypercall,
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sizeof(hypercall))) {
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_FDT((fdt_property(fdt, "hcall-instructions", hypercall,
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sizeof(hypercall))));
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}
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}
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_FDT((fdt_end_node(fdt)));
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}
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@ -2007,7 +2007,7 @@ int kvmppc_get_hypercall(CPUPPCState *env, uint8_t *buf, int buf_len)
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hc[2] = cpu_to_be32(0x48000008);
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hc[3] = cpu_to_be32(bswap32(0x3860ffff));
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return 0;
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return 1;
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}
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static inline int kvmppc_enable_hcall(KVMState *s, target_ulong hcall)
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