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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id ij24-20020a170902ab5800b001783f964fe3sm3191697plb.113.2022.09.13.09.12.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Sep 2022 09:12:07 -0700 (PDT) Date: Tue, 13 Sep 2022 16:12:04 +0000 From: Sean Christopherson To: "Kirill A. Shutemov" Cc: "Kirill A . Shutemov" , Hugh Dickins , Chao Peng , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, linux-kselftest@vger.kernel.org, Paolo Bonzini , Jonathan Corbet , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, Muchun Song , "Gupta, Pankaj" , Elena Reshetova Subject: Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory Message-ID: References: <20220818132421.6xmjqduempmxnnu2@box> <20220820002700.6yflrxklmpsavdzi@box.shutemov.name> <20220831142439.65q2gi4g2d2z4ofh@box.shutemov.name> <20220908011037.ez2cdorthqxkerwk@box.shutemov.name> <20220913132821.3ch5cv3rgdxqgz3i@box.shutemov.name> <20220913160046.rkz7uh6cpwy6wyzg@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220913160046.rkz7uh6cpwy6wyzg@box.shutemov.name> ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=DihabYGa; spf=pass (imf16.hostedemail.com: domain of seanjc@google.com designates 209.85.214.173 as permitted sender) smtp.mailfrom=seanjc@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663085530; a=rsa-sha256; cv=none; b=wulzS/XKcbOuUeVbHuxfoaHiotjCmsGy/hFi102KgQwzItIHWm1GNeWfnzOVbWHKGqdqha 5/XnFMT+0rlA8cL7extSXf+ZUHQIdsuX9aTRHiEcS2w/pce5sTsszE9bu7xJVHW/q/mSOZ Q8NGsfca5jDPdVgvAYR0QZOVyaQxVKo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663085530; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4GTld6ZU8MtCcyeBG9nWMSKRKMoB2xn8bpkZwXHEw2s=; b=7UNJe2R/a3TXBO/UIq+di06YBd8GHiVYtf97jh25JFrFy+OB3NNs06I03SIl/a4cUZpwxq QPseVpKwZipk/33FXpZ96c0YJokg+ReuycVjQksA5Wola8qumsF8BQserlVykCvJo8AV7C yBfAeXBAWIo6jJ35liAr7LUK/w83764= X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1F8BA180099 X-Rspam-User: Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=DihabYGa; spf=pass (imf16.hostedemail.com: domain of seanjc@google.com designates 209.85.214.173 as permitted sender) smtp.mailfrom=seanjc@google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: b64wzwex19dst4gpqsyycobdjwtfbsgy X-HE-Tag: 1663085529-927841 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: On Tue, Sep 13, 2022, Kirill A. Shutemov wrote: > On Tue, Sep 13, 2022 at 02:53:25PM +0000, Sean Christopherson wrote: > > > > Switching topics, what actually prevents mmapp() on the shim? I tried to follow, > > > > but I don't know these areas well enough. > > > > > > It has no f_op->mmap, so mmap() will fail with -ENODEV. See do_mmap(). > > > (I did not read the switch statement correctly at first. Note there are > > > two 'fallthrough' there.) > > > > Ah, validate_mmap_request(). Thought not implementing ->mmap() was the key, but > > couldn't find the actual check. > > validate_mmap_request() is in mm/nommu.c which is not relevant for real > computers. > > I was talking about this check: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/mmap.c#n1495 Hence the comment about 'fallthrough'. Thanks again!