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 f431a8cde7f1 ("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: f431a8cde7f1 ("powerpc/iommu: Reimplement the iommu_table_group_ops for pSeries") Cc: stable@vger.kernel.org Reviewed-by: Vaibhav Jain vaibhav@linux.ibm.com Reviewed-by: Ritesh Harjani (IBM) ritesh.list@gmail.com Signed-off-by: Amit Machhiwal amachhiw@linux.ibm.com --- Changes since v2: * Updated the patch description * v2: https://lore.kernel.org/all/20250129094033.2265211-1-amachhiw@linux.ibm.com/ Changes since v1: * Addressed review comments from Ritesh * v1: https://lore.kernel.org/all/20250109132053.158436-1-amachhiw@linux.ibm.com/

arch/powerpc/kvm/powerpc.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index ce1d91eed231..a7138eb18d59 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -543,26 +543,23 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = !hv_enabled; break; #ifdef CONFIG_KVM_MPIC case KVM_CAP_IRQ_MPIC: r = 1; break; #endif

#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: #ifdef CONFIG_KVM_XICS case KVM_CAP_IRQ_XICS: #endif case KVM_CAP_PPC_GET_CPU_CHAR: r = 1; break; #ifdef CONFIG_KVM_XIVE

base-commit: 6537cfb395f352782918d8ee7b7f10ba2cc3cbf2