Messages in this thread | | | Subject | Re: [PATCH 04/11] KVM: page track: add the framework of guest page tracking | From | Kai Huang <> | Date | Wed, 16 Dec 2015 15:33:18 +0800 |
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On 12/15/2015 04:46 PM, Xiao Guangrong wrote: > > > On 12/15/2015 03:06 PM, Kai Huang wrote: >> Hi Guangrong, >> >> I am starting to review this series, and should have some comments or >> questions, you can determine >> whether they are valuable :) > > Thank you very much for your review and breaking the silent on this > patchset. ;) > > >>> +static void page_track_slot_free(struct kvm_memory_slot *slot) >>> +{ >>> + int i; >>> + >>> + for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) >>> + if (slot->arch.gfn_track[i]) { >>> + kvfree(slot->arch.gfn_track[i]); >>> + slot->arch.gfn_track[i] = NULL; >>> + } >>> +} >>> + >>> +int kvm_page_track_create_memslot(struct kvm_memory_slot *slot, >>> + unsigned long npages) >>> +{ >>> + int i, pages = gfn_to_index(slot->base_gfn + npages - 1, >>> + slot->base_gfn, PT_PAGE_TABLE_LEVEL) + 1; >>> + >>> + for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) { >>> + slot->arch.gfn_track[i] = kvm_kvzalloc(pages * >>> + sizeof(*slot->arch.gfn_track[i])); >>> + if (!slot->arch.gfn_track[i]) >>> + goto track_free; >>> + } >>> + >>> + return 0; >>> + >>> +track_free: >>> + page_track_slot_free(slot); >>> + return -ENOMEM; >>> +} >> Is it necessary to use the 'unsigned long npages' pareameter? In my >> understanding you are going to > > The type, 'int', is used here as I followed the style of 'struct > kvm_lpage_info'. > > 4 bytes should be enough to track all users and signed type is good to > track > overflow. > >> track all GFNs in the memory slot anyway, right? If you want to keep >> npages, I think it's better to >> add a base_gfn as well otherwise you are assuming you are going to >> track the npages GFN starting >> from slot->base_gfn. > > Yes, any page in the memslot may be tracked so that there is a index > for every > page. > >> >>> + >>> +void kvm_page_track_free_memslot(struct kvm_memory_slot *free, >>> + struct kvm_memory_slot *dont) >>> +{ >>> + if (!dont || free->arch.gfn_track != dont->arch.gfn_track) >>> + page_track_slot_free(free); >>> +} >>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >>> index c04987e..ad4888a 100644 >>> --- a/arch/x86/kvm/x86.c >>> +++ b/arch/x86/kvm/x86.c >>> @@ -7838,6 +7838,8 @@ void kvm_arch_free_memslot(struct kvm *kvm, >>> struct kvm_memory_slot *free, >>> free->arch.lpage_info[i - 1] = NULL; >>> } >>> } >>> + >>> + kvm_page_track_free_memslot(free, dont); >>> } >>> int kvm_arch_create_memslot(struct kvm *kvm, struct >>> kvm_memory_slot *slot, >>> @@ -7886,6 +7888,9 @@ int kvm_arch_create_memslot(struct kvm *kvm, >>> struct kvm_memory_slot *slot, >>> } >>> } >>> + if (kvm_page_track_create_memslot(slot, npages)) >>> + goto out_free; >>> + >> Looks essentially you are allocating one int for all GFNs of the slot >> unconditionally. In my >> understanding for most of memory slots, we are not going to track >> them, so isn't it going to be >> wasteful of memory? >> > > Yes, hmm... maybe we can make the index as "unsigned short" then 1G > memory only needs 512k index > buffer. It is not so unacceptable. Those comments are really minor and don't bother on this :)
Thanks, -Kai
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