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Wed, 19 Jul 2023 08:39:10 -0700 (PDT) Date: Wed, 19 Jul 2023 08:39:09 -0700 In-Reply-To: Mime-Version: 1.0 References: <20230718234512.1690985-1-seanjc@google.com> <20230718234512.1690985-2-seanjc@google.com> Message-ID: Subject: Re: [RFC PATCH v11 01/29] KVM: Wrap kvm_gfn_range.pte in a per-action union From: Sean Christopherson To: Jarkko Sakkinen Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , "Matthew Wilcox (Oracle)" , Andrew Morton , Paul Moore , James Morris , "Serge E. Hallyn" , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Chao Peng , Fuad Tabba , Yu Zhang , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , Vlastimil Babka , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="us-ascii" X-Rspamd-Queue-Id: BF909180019 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: z8jjtx5b69ibqhzz9h4oz1f36oporqxj X-HE-Tag: 1689781151-817523 X-HE-Meta: U2FsdGVkX19MWtB8nVYdRdMscGs2sORWetvhbY3fiWLT969ZbvyBYcLujsGB0twbMMQSe2JSys70aEfQ47PszGu8z+lkS+kebO84Z9CKO5G7vqqXmwSkjoTHSqEmJkK/ULOyB8bLuBm3/WTL2CN9XDHI/5hZRjOXrJ/BOxT0aaoOJ7CxYrGcau1OUt4wtMWOHYZ9t83CxP18wA5vgwdkmq0EmDACz99e1iLBuAl7/OCkQGJxfjqceGihpkbTcqrKOTmq3L98qM/9Vs56URdNIP1HE0e0nCkkY2dFOLKGaSGKzv0alXxnzU5rU8V6rWVVR/QEXDRWqZG5kD/OJQtk0NNy3uAQJDoEy8vbEmXsW27N3A2jsKi7/vxPw/bODSHCvqlQct/HnPqZ9f6hO8mDSZtO4rYQkFUvi2GoVQpwdq95PKoZj3w8/9LrLGYeoNNAcTYiFwHtoac/lz5TD2u8UKAr8xwjSTJJEn1hBqELtIQdRBQZqxqSm/MNNfYogw0wF0pbAodGPzzQKKjmDcaptd7coRQXJGYNlr8+vmono3C+vcCqBI+Z+/J3h4bbLtwFVAL/Em+67uWzo2cTPEALU3M1zc+gs3WdZmP1KMg6kShLLB2J92RpQWJmJHm57vQDT17oh9fkIsxZhUd2AqeqIm/pQD3ozj6OFD/JAnVzZyGlZeokNSVhN6oDpE8S0pVMOF9p5gXLkKwQmux9r4W2oNdvnDoZReDR8wd1sCNYqNjuSDLzB5Ahre8y/U++xiGEOLbNH7zBm8lru3epn6T8FUhfzXDkBdonzh3DZ52Nkgs7WP2HJ91d5dnAo8DzN1MivyH9JSljO1P87AMG6U0cUOkDBr3LfmC5ooFXVPrUJvDHCGKkjouH/wUEfpVpMWebvQ1ZT4GO1ke7roFcEJaOigxqw2yeAXkw/RH0I0V+ZfD+ju8ii+Vxz/JyyrnUojsWkzB26iqynQGp2G22w3y 65E+OU/5 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 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 Wed, Jul 19, 2023, Jarkko Sakkinen wrote: > On Wed Jul 19, 2023 at 2:44 AM EEST, Sean Christopherson wrote: > > /* Huge pages aren't expected to be modified without first being zapped. */ > > - WARN_ON(pte_huge(range->pte) || range->start + 1 != range->end); > > + WARN_ON(pte_huge(range->arg.pte) || range->start + 1 != range->end); > > Not familiar with this code. Just checking whether whether instead > pr_{warn,err}() The "full" WARN is desirable, this is effecitvely an assert on the contract between the primary MMU, generic KVM code, and x86's TDP MMU. The .change_pte() mmu_notifier callback doesn't allow for hugepages, i.e. it's a (likely fatal) kernel bug if a hugepage is encountered at this point. Ditto for the "start + 1 == end" check, if that fails then generic KVM likely has a fatal bug. > combined with return false would be a more graceful option? The return value communicates whether or not a TLB flush is needed, not whether or not the operation was successful, i.e. there is no way to cancel the unexpected PTE change.