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AJvYcCWgwMV5jKKdl9IjEfkluWPZO0u5xg/2/+zJjcTOwFRm66dMaNYsKxjBZ9pcY9c2WdaiWoPJ3oYA1OK83mdnbPtlK9k= X-Gm-Message-State: AOJu0Ywv37PcKpelh+cuSyim+Akafy0b7sBGMCEJSwUby5REJ8z3PzK3 07ZrRcswwiG1/DZHr4qqq5JyRdrFdkyLm2UmzU2u0qmplxuy1HUTeBSTChcr8ltRE/+GChVPgQZ oQsk3G7mdo03HflvDY0mMwg== X-Google-Smtp-Source: AGHT+IEwc9XJlOMV7V25PTTSGoXOPbzFTCOo3wZFyrYqy6c/pJtVLczNwFnx8PjBfnZHFHlvbgx6nTmhxBNyQJb1uw== X-Received: from ackerleytng-ctop.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:13f8]) (user=ackerleytng job=sendgmr) by 2002:a05:6a00:91c8:b0:710:9d5d:f2ad with SMTP id d2e1a72fcca58-7109d5df3bcmr33362b3a.2.1722878350954; Mon, 05 Aug 2024 10:19:10 -0700 (PDT) Date: Mon, 05 Aug 2024 17:19:09 +0000 In-Reply-To: <20240801090117.3841080-5-tabba@google.com> (message from Fuad Tabba on Thu, 1 Aug 2024 10:01:11 +0100) Mime-Version: 1.0 Message-ID: Subject: Re: [RFC PATCH v2 04/10] KVM: Add KVM capability to check if guest_memfd can be mapped by the host From: Ackerley Tng To: Fuad Tabba 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, yu.c.zhang@linux.intel.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, mail@maciej.szmigiero.name, david@redhat.com, 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, tabba@google.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A78541A0015 X-Stat-Signature: gx5tzy7qwhke3ohoctgh57gymuh5r4ai X-Rspam-User: X-HE-Tag: 1722878352-192406 X-HE-Meta: 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 bNJyU5Xq 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Fuad Tabba writes: > Add the KVM capability KVM_CAP_GUEST_MEMFD_MAPPABLE, which is > true if mapping guest memory is supported by the host. > > Signed-off-by: Fuad Tabba > --- > include/uapi/linux/kvm.h | 3 ++- > virt/kvm/kvm_main.c | 4 ++++ > 2 files changed, 6 insertions(+), 1 deletion(-) > > Why do we need a cap for `KVM_CAP_GUEST_MEMFD_MAPPABLE` instead of just making guest_memfd mmap-able? Is this to prevent breaking userspace, because a user might be relying on guest_memfd being not mmap-able?