Commit f64c0398939483eb1d8951f24fbc21e94ed54457
Committed by
Marcelo Tosatti
Marcelo Tosatti
1 parent
0c29b2293b
Exists in
smarc-l5.0.0_1.0.0-ga
and in
5 other branches
KVM: set_memory_region: Identify the requested change explicitly
KVM_SET_USER_MEMORY_REGION forces __kvm_set_memory_region() to identify what kind of change is being requested by checking the arguments. The current code does this checking at various points in code and each condition being used there is not easy to understand at first glance. This patch consolidates these checks and introduces an enum to name the possible changes to clean up the code. Although this does not introduce any functional changes, there is one change which optimizes the code a bit: if we have nothing to change, the new code returns 0 immediately. Note that the return value for this case cannot be changed since QEMU relies on it: we noticed this when we changed it to -EINVAL and got a section mismatch error at the final stage of live migration. Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Showing 1 changed file with 44 additions and 20 deletions Side-by-side Diff
virt/kvm/kvm_main.c
| ... | ... | @@ -719,6 +719,24 @@ |
| 719 | 719 | } |
| 720 | 720 | |
| 721 | 721 | /* |
| 722 | + * KVM_SET_USER_MEMORY_REGION ioctl allows the following operations: | |
| 723 | + * - create a new memory slot | |
| 724 | + * - delete an existing memory slot | |
| 725 | + * - modify an existing memory slot | |
| 726 | + * -- move it in the guest physical memory space | |
| 727 | + * -- just change its flags | |
| 728 | + * | |
| 729 | + * Since flags can be changed by some of these operations, the following | |
| 730 | + * differentiation is the best we can do for __kvm_set_memory_region(): | |
| 731 | + */ | |
| 732 | +enum kvm_mr_change { | |
| 733 | + KVM_MR_CREATE, | |
| 734 | + KVM_MR_DELETE, | |
| 735 | + KVM_MR_MOVE, | |
| 736 | + KVM_MR_FLAGS_ONLY, | |
| 737 | +}; | |
| 738 | + | |
| 739 | +/* | |
| 722 | 740 | * Allocate some memory and give it an address in the guest physical address |
| 723 | 741 | * space. |
| 724 | 742 | * |
| ... | ... | @@ -737,6 +755,7 @@ |
| 737 | 755 | struct kvm_memory_slot old, new; |
| 738 | 756 | struct kvm_memslots *slots = NULL, *old_memslots; |
| 739 | 757 | bool old_iommu_mapped; |
| 758 | + enum kvm_mr_change change; | |
| 740 | 759 | |
| 741 | 760 | r = check_memory_region_flags(mem); |
| 742 | 761 | if (r) |
| 743 | 762 | |
| 744 | 763 | |
| 745 | 764 | |
| ... | ... | @@ -780,17 +799,30 @@ |
| 780 | 799 | |
| 781 | 800 | old_iommu_mapped = old.npages; |
| 782 | 801 | |
| 783 | - /* | |
| 784 | - * Disallow changing a memory slot's size or changing anything about | |
| 785 | - * zero sized slots that doesn't involve making them non-zero. | |
| 786 | - */ | |
| 787 | 802 | r = -EINVAL; |
| 788 | - if (npages && old.npages && npages != old.npages) | |
| 803 | + if (npages) { | |
| 804 | + if (!old.npages) | |
| 805 | + change = KVM_MR_CREATE; | |
| 806 | + else { /* Modify an existing slot. */ | |
| 807 | + if ((mem->userspace_addr != old.userspace_addr) || | |
| 808 | + (npages != old.npages)) | |
| 809 | + goto out; | |
| 810 | + | |
| 811 | + if (base_gfn != old.base_gfn) | |
| 812 | + change = KVM_MR_MOVE; | |
| 813 | + else if (new.flags != old.flags) | |
| 814 | + change = KVM_MR_FLAGS_ONLY; | |
| 815 | + else { /* Nothing to change. */ | |
| 816 | + r = 0; | |
| 817 | + goto out; | |
| 818 | + } | |
| 819 | + } | |
| 820 | + } else if (old.npages) { | |
| 821 | + change = KVM_MR_DELETE; | |
| 822 | + } else /* Modify a non-existent slot: disallowed. */ | |
| 789 | 823 | goto out; |
| 790 | - if (!npages && !old.npages) | |
| 791 | - goto out; | |
| 792 | 824 | |
| 793 | - if ((npages && !old.npages) || (base_gfn != old.base_gfn)) { | |
| 825 | + if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) { | |
| 794 | 826 | /* Check for overlaps */ |
| 795 | 827 | r = -EEXIST; |
| 796 | 828 | kvm_for_each_memslot(slot, kvm->memslots) { |
| 797 | 829 | |
| ... | ... | @@ -808,20 +840,12 @@ |
| 808 | 840 | new.dirty_bitmap = NULL; |
| 809 | 841 | |
| 810 | 842 | r = -ENOMEM; |
| 811 | - | |
| 812 | - /* | |
| 813 | - * Allocate if a slot is being created. If modifying a slot, | |
| 814 | - * the userspace_addr cannot change. | |
| 815 | - */ | |
| 816 | - if (!old.npages) { | |
| 843 | + if (change == KVM_MR_CREATE) { | |
| 817 | 844 | new.user_alloc = user_alloc; |
| 818 | 845 | new.userspace_addr = mem->userspace_addr; |
| 819 | 846 | |
| 820 | 847 | if (kvm_arch_create_memslot(&new, npages)) |
| 821 | 848 | goto out_free; |
| 822 | - } else if (npages && mem->userspace_addr != old.userspace_addr) { | |
| 823 | - r = -EINVAL; | |
| 824 | - goto out_free; | |
| 825 | 849 | } |
| 826 | 850 | |
| 827 | 851 | /* Allocate page dirty bitmap if needed */ |
| ... | ... | @@ -830,7 +854,7 @@ |
| 830 | 854 | goto out_free; |
| 831 | 855 | } |
| 832 | 856 | |
| 833 | - if (!npages || base_gfn != old.base_gfn) { | |
| 857 | + if ((change == KVM_MR_DELETE) || (change == KVM_MR_MOVE)) { | |
| 834 | 858 | r = -ENOMEM; |
| 835 | 859 | slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots), |
| 836 | 860 | GFP_KERNEL); |
| ... | ... | @@ -881,7 +905,7 @@ |
| 881 | 905 | * slots (size changes, userspace addr changes) is disallowed above, |
| 882 | 906 | * so any other attribute changes getting here can be skipped. |
| 883 | 907 | */ |
| 884 | - if (npages) { | |
| 908 | + if (change != KVM_MR_DELETE) { | |
| 885 | 909 | if (old_iommu_mapped && |
| 886 | 910 | ((new.flags ^ old.flags) & KVM_MEM_READONLY)) { |
| 887 | 911 | kvm_iommu_unmap_pages(kvm, &old); |
| ... | ... | @@ -896,7 +920,7 @@ |
| 896 | 920 | } |
| 897 | 921 | |
| 898 | 922 | /* actual memory is freed via old in kvm_free_physmem_slot below */ |
| 899 | - if (!npages) { | |
| 923 | + if (change == KVM_MR_DELETE) { | |
| 900 | 924 | new.dirty_bitmap = NULL; |
| 901 | 925 | memset(&new.arch, 0, sizeof(new.arch)); |
| 902 | 926 | } |