| Date | Mon, 30 Oct 2023 16:11:47 +0800 | From | Chao Gao <> | Subject | Re: [PATCH v13 13/35] KVM: Introduce per-page memory attributes |
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On Fri, Oct 27, 2023 at 11:21:55AM -0700, Sean Christopherson wrote: >From: Chao Peng <chao.p.peng@linux.intel.com> > >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 So, the changelog is out-of-date and needs an update.
> >+ >+:Capability: KVM_CAP_MEMORY_ATTRIBUTES >+:Architectures: x86 >+:Type: vm ioctl >+:Parameters: struct kvm_memory_attributes(in)
^ add one space here?
>+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")
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