(2011/11/14 19:22), Avi Kivity wrote:
+ * + * Generally speaking, if there are not so many dirty pages compared to the + * number of shadow pages, we should use the latter. + * + * Note that letting others write into a page marked dirty in the old bitmap + * by using the remaining tlb entry is not a problem. That page will become + * write protected again when we flush the tlb and then be reported dirty to + * the user space by copying the old bitmap. + */ +static void write_protect_slot(struct kvm *kvm, + struct kvm_memory_slot *memslot, + unsigned long *dirty_bitmap, + unsigned long nr_dirty_pages) +{ + /* Not many dirty pages compared to # of shadow pages. */ + if (nr_dirty_pages< kvm->arch.n_used_mmu_pages) {Seems a reasonable heuristic. In particular, this is always true for vga, yes? That will get the code exercised.
Almost always yes, once the guest warms up and shadow pages are allocated. Takuya
+ unsigned long gfn_offset; + + for_each_set_bit(gfn_offset, dirty_bitmap, memslot->npages) { + unsigned long gfn = memslot->base_gfn + gfn_offset; + + spin_lock(&kvm->mmu_lock); + kvm_mmu_rmap_write_protect(kvm, gfn, memslot); + spin_unlock(&kvm->mmu_lock); + } + kvm_flush_remote_tlbs(kvm); + } else { + spin_lock(&kvm->mmu_lock); + kvm_mmu_slot_remove_write_access(kvm, memslot->id); + spin_unlock(&kvm->mmu_lock); + } +} +
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