Commit b4392813 authored by Amit Machhiwal's avatar Amit Machhiwal Committed by Madhavan Srinivasan
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KVM: PPC: Enable CAP_SPAPR_TCE_VFIO on pSeries KVM guests 



Currently on book3s-hv, the capability KVM_CAP_SPAPR_TCE_VFIO is only
available for KVM Guests running on PowerNV and not for the KVM guests
running on pSeries hypervisors. This prevents a pSeries L2 guest from
leveraging the in-kernel acceleration for H_PUT_TCE_INDIRECT and
H_STUFF_TCE hcalls that results in slow startup times for large memory
guests.

Support for VFIO on pSeries was restored in commit f431a8cd
("powerpc/iommu: Reimplement the iommu_table_group_ops for pSeries"),
making it possible to re-enable this capability on pSeries hosts.

This change enables KVM_CAP_SPAPR_TCE_VFIO for nested PAPR guests on
pSeries, while maintaining the existing behavior on PowerNV. Booting an
L2 guest with 128GB of memory shows an average 11% improvement in
startup time.

Fixes: f431a8cd ("powerpc/iommu: Reimplement the iommu_table_group_ops for pSeries")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarVaibhav Jain <vaibhav@linux.ibm.com>
Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: default avatarAmit Machhiwal <amachhiw@linux.ibm.com>
Signed-off-by: default avatarMadhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250220070002.1478849-1-amachhiw@linux.ibm.com
parent 7e67ef88

arch/powerpc/kvm/powerpc.c

+1 −4
Original line number Diff line number Diff line
@@ -550,12 +550,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) 


#ifdef CONFIG_PPC_BOOK3S_64

	case KVM_CAP_SPAPR_TCE:

		fallthrough;

	case KVM_CAP_SPAPR_TCE_64:

		r = 1;

		break;

	case KVM_CAP_SPAPR_TCE_VFIO:

		r = !!cpu_has_feature(CPU_FTR_HVMODE);

		break;

	case KVM_CAP_PPC_RTAS:

	case KVM_CAP_PPC_FIXUP_HCALL:

	case KVM_CAP_PPC_ENABLE_HCALL: