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From: | Maciej S. Szmigiero |
Subject: | Re: [PATCH v4 12/12] KVM: Expose KVM_MEM_PRIVATE |
Date: | Tue, 25 Jan 2022 21:20:39 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 |
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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