Messages in this thread | | | Date | Wed, 21 Dec 2022 13:13:48 -0800 | Subject | Re: [PATCH V5 5/7] KVM: selftests: add library for creating/interacting with SEV guests | From | Ackerley Tng <> |
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> +static void encrypt_region(struct kvm_vm *vm, struct > userspace_mem_region *region) > +{ > + const struct sparsebit *protected_phy_pages = > + region->protected_phy_pages; > + const uint64_t memory_size = region->region.memory_size; > + const vm_paddr_t gpa_start = region->region.guest_phys_addr; > + sparsebit_idx_t pg = 0; > + > + sev_register_user_region(vm, region); > + > + while (pg < (memory_size / vm->page_size)) { > + sparsebit_idx_t nr_pages; > + > + if (sparsebit_is_clear(protected_phy_pages, pg)) { > + pg = sparsebit_next_set(protected_phy_pages, pg); > + if (!pg) > + break; > + } > + > + nr_pages = sparsebit_next_clear(protected_phy_pages, pg) - pg; > + if (nr_pages <= 0) > + nr_pages = 1;
I think this may not be correct in the case where the sparsebit has the range [x, 2**64-1] (inclusive) set. In that case, sparsebit_next_clear() will return 0, but the number of pages could be more than 1.
> + > + sev_launch_update_data(vm, gpa_start + pg * vm->page_size,
Computing the beginning of the gpa range with
gpa_start + pg * vm->page_size
only works if this memory region's gpa_start is 0.
> + nr_pages * vm->page_size); > + pg += nr_pages; > + } > +}
Here's a suggestion (I'm using this on a TDX version of this patch)
/** * Iterate over set ranges within sparsebit @s. In each iteration, * @range_begin and @range_end will take the beginning and end of the set range, * which are of type sparsebit_idx_t. * * For example, if the range [3, 7] (inclusive) is set, within the iteration, * @range_begin will take the value 3 and @range_end will take the value 7. * * Ensure that there is at least one bit set before using this macro with * sparsebit_any_set(), because sparsebit_first_set() will abort if none are * set. */ #define sparsebit_for_each_set_range(s, range_begin, range_end) \ for (range_begin = sparsebit_first_set(s), \ range_end = \ sparsebit_next_clear(s, range_begin) - 1; \ range_begin && range_end; \ range_begin = sparsebit_next_set(s, range_end), \ range_end = \ sparsebit_next_clear(s, range_begin) - 1) /* * sparsebit_next_clear() can return 0 if [x, 2**64-1] are all set, and the -1 * would then cause an underflow back to 2**64 - 1. This is expected and * correct. * * If the last range in the sparsebit is [x, y] and we try to iterate, * sparsebit_next_set() will return 0, and sparsebit_next_clear() will try and * find the first range, but that's correct because the condition expression * would cause us to quit the loop. */
static void encrypt_region(struct kvm_vm *vm, struct userspace_mem_region *region) { const struct sparsebit *protected_phy_pages = region->protected_phy_pages; const vm_paddr_t gpa_base = region->region.guest_phys_addr; const sparsebit_idx_t lowest_page_in_region = gpa_base >> vm->page_shift;
sparsebit_idx_t i; sparsebit_idx_t j;
if (!sparsebit_any_set(protected_phy_pages)) return;
sev_register_user_region(vm, region);
sparsebit_for_each_set_range(protected_phy_pages, i, j) { const uint64_t size_to_load = (j - i + 1) * vm->page_size; const uint64_t offset = (i - lowest_page_in_region) * vm->page_size; const uint64_t gpa = gpa_base + offset;
sev_launch_update_data(vm, gpa, size_to_load); } }
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