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Wed, 26 Jul 2023 08:59:55 -0700 (PDT) Date: Wed, 26 Jul 2023 08:59:53 -0700 In-Reply-To: Mime-Version: 1.0 References: <20230718234512.1690985-1-seanjc@google.com> <20230718234512.1690985-9-seanjc@google.com> Message-ID: Subject: Re: [RFC PATCH v11 08/29] KVM: Introduce per-page memory attributes From: Sean Christopherson To: Xu Yilun 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 , Jarkko Sakkinen , 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-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3798DA001E X-Stat-Signature: kh8jfbt8w9c4dqniqtbap957h695qg8k X-HE-Tag: 1690387195-963981 X-HE-Meta: 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 NcUs2s+c 73Mvqa9z93KebazZs/GWUJIFQn724zKCQhyVwBXt2yI9DLelEMugN/kiQWSSYcxx20NnMDJIMeFXrEkRLo3qmgP9Y3JiHr8RwAduE3Fw4hdKkjuLs7FdIvWOLKIpB+3Kclv6alggICc+ZEQ6oecgmSM2HmEbLVSJed3Af5Rzvh+Z75usV9Ic4SIScTc737O0EY1dhLcADEmPpolmnGCyhjYT9Sneg9Q5V4PEExYnCTXOEfYHvT8EOeAG1uh20QAKihTfinN4Fq2+N1ZsTtb9gMM7NhUnKdwTK9lWy919d7lMlnz1uLUkPbYrQ/XMvFOyV7VK9ldWrfIj1J/hyFuxvw9m2zwu7eyWEGyFz2Z6/P9ZWVM5i5BzJguQqM6eaM6FbzYhZvp9nJ2TM865CXsV09vd6kev3Rta8pFofObSX+5ddKrD1YSsuoRRIUzGkf9zO65TMPkAdxqP4I2GsVtQPHP0jvJMGRgWchhefq59BWqO2MuoHeh9915tTr7p2eNrSgq9BrFrTkLOJTzz1OqztzDdSKCu4Z3ZJz9g5K1cAOBl0Wz3ww7ZQymtHBvM7J0KQbVuesSVTVjuIdI1R3oiG+ZnF2+inxzTlkgnvyWC35FaD/cMVvyEE9apSGlViuu0xbq76Ey2wNij9eoeC4sZy5+KX5A== 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 Mon, Jul 24, 2023, Xu Yilun wrote: > On 2023-07-18 at 16:44:51 -0700, Sean Christopherson wrote: > > @@ -1346,6 +1350,9 @@ static void kvm_destroy_vm(struct kvm *kvm) > > kvm_free_memslots(kvm, &kvm->__memslots[i][0]); > > kvm_free_memslots(kvm, &kvm->__memslots[i][1]); > > } > > +#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES > > + xa_destroy(&kvm->mem_attr_array); > > +#endif > > Is it better to make the destruction in reverse order from the creation? Yeah. It _shoudn't_ matter, but there's no reason not keep things tidy and consistent. > To put xa_destroy(&kvm->mem_attr_array) after cleanup_srcu_struct(&kvm->srcu), > or put xa_init(&kvm->mem_attr_array) after init_srcu_struct(&kvm->irq_srcu). The former, because init_srcu_struct() can fail (allocates memory), whereas xa_init() is a "pure" initialization routine. > > cleanup_srcu_struct(&kvm->irq_srcu); > > cleanup_srcu_struct(&kvm->srcu); > > kvm_arch_free_vm(kvm); > > @@ -2346,6 +2353,145 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm, > > } > > #endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */ > > [...] > > > +static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, > > + struct kvm_memory_attributes *attrs) > > +{ > > + gfn_t start, end; > > + > > + /* flags is currently not used. */ > > + if (attrs->flags) > > + return -EINVAL; > > + if (attrs->attributes & ~kvm_supported_mem_attributes(kvm)) > > + return -EINVAL; > > + if (attrs->size == 0 || attrs->address + attrs->size < attrs->address) > > + return -EINVAL; > > + if (!PAGE_ALIGNED(attrs->address) || !PAGE_ALIGNED(attrs->size)) > > + return -EINVAL; > > + > > + start = attrs->address >> PAGE_SHIFT; > > + end = (attrs->address + attrs->size - 1 + PAGE_SIZE) >> PAGE_SHIFT; > > As the attrs->address/size are both garanteed to be non-zero, non-wrap > and page aligned in prevous check. Is it OK to simplify the calculation, > like: > > end = (attrs->address + attrs->size) >> PAGE_SHIFT; Yes, that should work. Chao, am I missing something? Or did we just end up with unnecessarly convoluted code as things evolved? > > + > > + if (WARN_ON_ONCE(start == end)) > > + return -EINVAL; > > Also, is this check possible to be hit? Maybe remove it? It should be impossible to, hence the WARN. I added the check for two reasons: (1) to help document that end is exclusive, and (2) to guard against future bugs.