Messages in this thread | | | Date | Tue, 25 Jan 2022 21:20:39 +0100 | From | "Maciej S. Szmigiero" <> | Subject | Re: [PATCH v4 12/12] KVM: Expose KVM_MEM_PRIVATE |
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On 18.01.2022 14:21, Chao Peng wrote: > KVM_MEM_PRIVATE is not exposed by default but architecture code can turn > on it by implementing kvm_arch_private_memory_supported(). > > Also private memslot cannot be movable and the same file+offset can not > be mapped into different GFNs. > > Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com> > Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com> > --- (..) > > static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id, > - gfn_t start, gfn_t end) > + struct file *file, > + gfn_t start, gfn_t end, > + loff_t start_off, loff_t end_off) > { > struct kvm_memslot_iter iter; > + struct kvm_memory_slot *slot; > + struct inode *inode; > + int bkt; > > kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) { > if (iter.slot->id != id) > return true; > } > > + /* Disallow mapping the same file+offset into multiple gfns. */ > + if (file) { > + inode = file_inode(file); > + kvm_for_each_memslot(slot, bkt, slots) { > + if (slot->private_file && > + file_inode(slot->private_file) == inode && > + !(end_off <= slot->private_offset || > + start_off >= slot->private_offset > + + (slot->npages >> PAGE_SHIFT))) > + return true; > + } > + }
That's a linear scan of all memslots on each CREATE (and MOVE) operation with a fd - we just spent more than a year rewriting similar linear scans into more efficient operations in KVM.
Thanks, Maciej
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