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Mon, 30 Oct 2023 09:10:49 -0700 (PDT) Date: Mon, 30 Oct 2023 16:10:48 +0000 In-Reply-To: Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-14-seanjc@google.com> Message-ID: Subject: Re: [PATCH v13 13/35] KVM: Introduce per-page memory attributes From: Sean Christopherson To: Chao Gao Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , 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-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , "=?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?=" , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="us-ascii" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A4E7D160029 X-Stat-Signature: rmpfe54gjikrgnmzz8wnuz4r38x4iagk X-Rspam-User: X-HE-Tag: 1698682250-911858 X-HE-Meta: U2FsdGVkX1/hR2EwYoP15TBtEgio4O09BE1gUW1ZUEhk9aAoO/LSZuSHxeaIxxC4ce2COkPeLiF6Iu4SurMWX5zE718Ld/Qc7vSTAlOWV0yAYsW5XyC70D3yYaX06gpp4NMl+msHxlE0FYiXp/LmONUn0CwzFCxtLj5E5Npk23bIQUma7psVSeok+SchLKzrQJ1klWF3vfEx75IqzNCXB4ktaapE0r7G99Um3dPcG0moysc/I4hJ741s/12e6iKObFs518J8bT13HfikLbijNdYUFkVyQT32sZaH3qKj4vH5rJI+mfZM5ug0SS8FPd19qcW/sPaaJjOKOnl/aa0LDcYZFRBObWIezZcFJTeVXdldTb8qqAleZFkOxgbh+dWc2YPKJmNgWE4iBs5T6b1f5l9nUNLu7YLgTvSFb6kS2DiRjBtm5M9XAFNEfrjOmo/f80S0RAp6HDHjmGTKReiFnktXi4uDd3Tj/ochEwHfHnbC3iMJw5GXdQzO0clxmCA7T00NCJUbdVr0lN0PgZHMIq4gJHGEuLbAgG5P2SjAiH4TR8p1bSMqUKejJgceMjs2Zptq/rW3ICTWFDP6jtxW2H1NkXuvuty9lm/bGW1/Jbom0IFUoNQvbr2xtuVSLx3aQMYaFJh0+Q7NAHTYjQwX7dJBVnlwEFJSojYlnMxOFMdryh/TpqBSOUz5ib6rtnNs6AmqssPcE2vIz3jTpyi1mQin1SHuJI/EbFNFClj2hAdC1Q0KQGFBZKzWd/rC0q3ubIEHBoN88p1E+KQVenPhwRDB27llt9wW4s5pXTOtc1KXYZihvaXGrHZGqGZUxchShKJaZxOj7Di1g8+6hd8BS9f6BoL2EXyoJChQYwyr4Mg7Ep/KRlXkLkGDj5oko/doA3/p3DSW1MZuQ52AGJtI98Ad2GPGmHIsglH+SbaNwMDBKPD3rgfYKaFyzyRwU3qwo5eM0sRMBUmdZ+lbEwj xAPCQj2B 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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: List-Subscribe: List-Unsubscribe: On Mon, Oct 30, 2023, Chao Gao wrote: > On Fri, Oct 27, 2023 at 11:21:55AM -0700, Sean Christopherson wrote: > >From: Chao Peng > > > >In confidential computing usages, whether a page is private or shared is > >necessary information for KVM to perform operations like page fault > >handling, page zapping etc. There are other potential use cases for > >per-page memory attributes, e.g. to make memory read-only (or no-exec, > >or exec-only, etc.) without having to modify memslots. > > > >Introduce two ioctls (advertised by KVM_CAP_MEMORY_ATTRIBUTES) to allow > >userspace to operate on the per-page memory attributes. > > - KVM_SET_MEMORY_ATTRIBUTES to set the per-page memory attributes to > > a guest memory range. > > > - KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES to return the KVM supported > > memory attributes. > > This ioctl() is already removed. So, the changelog is out-of-date and needs > an update. Doh, I lost track of this and the fixup for KVM_CAP_MEMORY_ATTRIBUTES below. > >+:Capability: KVM_CAP_MEMORY_ATTRIBUTES > >+:Architectures: x86 > >+:Type: vm ioctl > >+:Parameters: struct kvm_memory_attributes(in) > > ^ add one space here? Ah, yeah, that does appear to be the standard. > > > >+static bool kvm_pre_set_memory_attributes(struct kvm *kvm, > >+ struct kvm_gfn_range *range) > >+{ > >+ /* > >+ * Unconditionally add the range to the invalidation set, regardless of > >+ * whether or not the arch callback actually needs to zap SPTEs. E.g. > >+ * if KVM supports RWX attributes in the future and the attributes are > >+ * going from R=>RW, zapping isn't strictly necessary. Unconditionally > >+ * adding the range allows KVM to require that MMU invalidations add at > >+ * least one range between begin() and end(), e.g. allows KVM to detect > >+ * bugs where the add() is missed. Rexlaing the rule *might* be safe, > > ^^^^^^^^ Relaxing > > >@@ -4640,6 +4850,17 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) > > case KVM_CAP_BINARY_STATS_FD: > > case KVM_CAP_SYSTEM_EVENT_DATA: > > return 1; > >+#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES > >+ case KVM_CAP_MEMORY_ATTRIBUTES: > >+ u64 attrs = kvm_supported_mem_attributes(kvm); > >+ > >+ r = -EFAULT; > >+ if (copy_to_user(argp, &attrs, sizeof(attrs))) > >+ goto out; > >+ r = 0; > >+ break; > > This cannot work, e.g., no @argp in this function and is fixed by a later commit: > > fcbef1e5e5d2 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory") I'll post a fixup patch for all of these, thanks much!