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Wed, 21 May 2025 03:29:51 -0700 (PDT) MIME-Version: 1.0 References: <20250513163438.3942405-1-tabba@google.com> <20250513163438.3942405-15-tabba@google.com> <2084504e-2a11-404a-bbe8-930384106f53@redhat.com> In-Reply-To: From: Fuad Tabba Date: Wed, 21 May 2025 11:29:14 +0100 X-Gm-Features: AX0GCFtp1C5WS7koE3vXh__qYSYt1ZsWt-4VJOAZFQTaZFrfaysMtz-msa--LUE Message-ID: Subject: Re: [PATCH v9 14/17] KVM: arm64: Enable mapping guest_memfd in arm64 To: David Hildenbrand Cc: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: DA856140011 X-Rspamd-Server: rspam09 X-Stat-Signature: krts8fgjob3bmhg13rn93tsbcyociopz X-HE-Tag: 1747823392-724272 X-HE-Meta: U2FsdGVkX19/mI19rmtAIZdDGMn7dO5QNQQqb98yNf/foaQ2tSQhn6rJbkEwgyOLMt6y47iz2FW7WFYUuJyW/2IyFKlLGts88HRcCpEvKiZ+1Dt2N1jaeGb4N8+pxhyZuswjtWmkBtPv8yQ5Kb0qYF0vqglojkCHaX4h47ROcuQcXEV4KBNzYVcfDbDXzEW9jX64X6cegfpuz3UPlUjxm/ATApLrvzYfhKgGpf2qSRdSW6FYBuM7wkCTwkptb2QBTLZo2d47NlnhtIYIaHXr/xOLI4eNVvBKQpN9yfBRk3HImQhIQt8etlsYcvuITRBKjVW5xwEHS1mN+pChCRUGVBnw1CdFe5IX8FQpUgKI/ORSaSfIJGbZjTbFYyhZ6ZM7pRFChuXMOpB2Vuq1yYvAG6jXrzTsAbYdC9mTlA7xzCTNYn0/R7GCGNRYdWO5aHDlga6Rz/1YBvY7KVUq116PmDCQlTuTNLTXsyDHQ06u2ZsaWJD6Wwd6ei5/uv3vlOchif5n9OMRtRmgqIx8VeWGnfxP9W9VVo8IUVZbpFj/0P/oLaoYiyq9RNhfJAspfnp5afNV6Su8VPsmD+o7Mo2lnZU/7UjUJdiCps3HnRDlnFhnPjVmqMr7fvHQpSikWmFGUw951jSH4kgqwG0vPdqMwrLxxcQoaJC9zHh+6wiNiuGik1aFgvr8bfJdxLBejnXnjgB4OmHIWVHHU5KGLfWy0OIftyuFX6RipOCAT3YiWzdL1nSfxgwjrA4HE0gYKnKJZGG2k4vIjm7s/RnPBUDqF37cFZkeGegend8a+iuTMze/Y0JrMfNiNW4EpQJtGNueN8gq3zx0+YThQpq6uRSqOcfly5nCfCOCFq75jsmn4XlWWWVyhxPOpo9mt2Em6z4yooKnXHn22Aojyy8iJ89dlHI/v/5yukxNL68U4o3CCYYpoBJ8+Bv3veUXJEf3Arkjqly80ik/2qHo6R7GJ6l N3h/M2je FywzKs88DFQvFT1YRhHEa+6hdBNR1+Xn6quKMjlhfrJ75L+AmgSjLA1YnBAoUS9ZQOc2yYbFsmJht1DFAgvkTYP9atvrAY1RclmHP8cVXUjnnIfqYlm06ml6LHhILr2bcS4KKMsymuGpdI6UzrxK0JBrEQag/Py3J6W7YjbBDAMDnd2Z5JgGIGdxRl5rR63jehCBtJC+EvEiQVePnQRA4dzXFs6ebbPv9SsZWQASHZKLzIB2KMDNqndX1TF5f7kIjQ2aWINtFao3qlw8dVVFBlx8h+etE1KtYZ6blAT4ZKyVRrOaPDzeBfz3G4IuEQupGZ0jITEsU8PzoXbjrOnNlfhiVNl79tMvp2QbIJaDIVwYOjNw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 21 May 2025 at 11:26, David Hildenbrand wrote: > > On 21.05.25 12:12, Fuad Tabba wrote: > > Hi David, > > > > On Wed, 21 May 2025 at 09:05, David Hildenbrand wrote: > >> > >> On 13.05.25 18:34, Fuad Tabba wrote: > >>> Enable mapping guest_memfd in arm64. For now, it applies to all > >>> VMs in arm64 that use guest_memfd. In the future, new VM types > >>> can restrict this via kvm_arch_gmem_supports_shared_mem(). > >>> > >>> Signed-off-by: Fuad Tabba > >>> --- > >>> arch/arm64/include/asm/kvm_host.h | 10 ++++++++++ > >>> arch/arm64/kvm/Kconfig | 1 + > >>> 2 files changed, 11 insertions(+) > >>> > >>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > >>> index 08ba91e6fb03..2514779f5131 100644 > >>> --- a/arch/arm64/include/asm/kvm_host.h > >>> +++ b/arch/arm64/include/asm/kvm_host.h > >>> @@ -1593,4 +1593,14 @@ static inline bool kvm_arch_has_irq_bypass(void) > >>> return true; > >>> } > >>> > >>> +static inline bool kvm_arch_supports_gmem(struct kvm *kvm) > >>> +{ > >>> + return IS_ENABLED(CONFIG_KVM_GMEM); > >>> +} > >>> + > >>> +static inline bool kvm_arch_vm_supports_gmem_shared_mem(struct kvm *kvm) > >>> +{ > >>> + return IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM); > >>> +} > >>> + > >>> #endif /* __ARM64_KVM_HOST_H__ */ > >>> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig > >>> index 096e45acadb2..8c1e1964b46a 100644 > >>> --- a/arch/arm64/kvm/Kconfig > >>> +++ b/arch/arm64/kvm/Kconfig > >>> @@ -38,6 +38,7 @@ menuconfig KVM > >>> select HAVE_KVM_VCPU_RUN_PID_CHANGE > >>> select SCHED_INFO > >>> select GUEST_PERF_EVENTS if PERF_EVENTS > >>> + select KVM_GMEM_SHARED_MEM > >>> help > >>> Support hosting virtualized guest machines. > >>> > >> > >> Do we have to reject somewhere if we are given a guest_memfd that was > >> *not* created using the SHARED flag? Or will existing checks already > >> reject that? > > > > We don't reject, but I don't think we need to. A user can create a > > guest_memfd that's private in arm64, it would just be useless. > > But the arm64 fault routine would not be able to handle that properly, no? Actually it would. The function user_mem_abort() doesn't care whether it's private or shared. It would fault it into the guest correctly regardless. Thanks, /fuad > -- > Cheers, > > David / dhildenb >