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suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, shahuang@redhat.com, lpieralisi@kernel.org, david@redhat.com, ddutile@redhat.com, seanjc@google.com, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, kjaju@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, zhiw@nvidia.com, mochs@nvidia.com, udhoke@nvidia.com, dnigam@nvidia.com, alex.williamson@redhat.com, sebastianene@google.com, coltonlewis@google.com, kevin.tian@intel.com, yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org, gshan@redhat.com, linux-mm@kvack.org, tabba@google.com, qperret@google.com, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maobibo@loongson.cn Subject: Re: [PATCH v9 6/6] KVM: arm64: Expose new KVM cap for cacheable PFNMAP Message-ID: <20250704134413.GE1410929@nvidia.com> References: 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 XUkhaAGi 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ability to safely do the cacheable mapping of PFNMAP is contingent > on S2FWB and ARM64_HAS_CACHE_DIC. S2FWB allows KVM to avoid flushing > the D cache, ARM64_HAS_CACHE_DIC allows KVM to avoid flushing the icache > and turns icache_inval_pou() into a NOP. The cap would be false if > those requirements are missing and is checked by making use of > kvm_arch_supports_cacheable_pfnmap. > > This capability would allow userspace to discover the support. > It could for instance be used by userspace to prevent live-migration > across FWB and non-FWB hosts. > > CC: Catalin Marinas > CC: Jason Gunthorpe > CC: Oliver Upton > CC: David Hildenbrand > Suggested-by: Marc Zyngier > Signed-off-by: Ankit Agrawal > --- > Documentation/virt/kvm/api.rst | 13 ++++++++++++- > arch/arm64/kvm/arm.c | 7 +++++++ > include/uapi/linux/kvm.h | 1 + > 3 files changed, 20 insertions(+), 1 deletion(-) I don't know if any VMM will ever use this, but it looks OK Reviewed-by: Jason Gunthorpe Jason