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| author | Paolo Bonzini <pbonzini@redhat.com> | 2022-12-12 11:36:53 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-12-27 12:00:49 +0100 |
| commit | feb84f6daa7e7d51444d13fa65df7d5562fd0075 (patch) | |
| tree | 7641ca1f30e36e72f660c62f2d296f48b0dec054 /tools | |
| parent | KVM: selftests: Use magic value to signal ucall_alloc() failure (diff) | |
| download | linux-feb84f6daa7e7d51444d13fa65df7d5562fd0075.tar.xz linux-feb84f6daa7e7d51444d13fa65df7d5562fd0075.zip | |
KVM: selftests: document the default implementation of vm_vaddr_populate_bitmap
Explain the meaning of the bit manipulations of vm_vaddr_populate_bitmap.
These correspond to the "canonical addresses" of x86 and other
architectures, but that is not obvious.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/kvm/lib/kvm_util.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index c88c3ace16d2..bd892a814951 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c @@ -186,6 +186,15 @@ const struct vm_guest_mode_params vm_guest_mode_params[] = { _Static_assert(sizeof(vm_guest_mode_params)/sizeof(struct vm_guest_mode_params) == NUM_VM_MODES, "Missing new mode params?"); +/* + * Initializes vm->vpages_valid to match the canonical VA space of the + * architecture. + * + * The default implementation is valid for architectures which split the + * range addressed by a single page table into a low and high region + * based on the MSB of the VA. On architectures with this behavior + * the VA region spans [0, 2^(va_bits - 1)), [-(2^(va_bits - 1), -1]. + */ __weak void vm_vaddr_populate_bitmap(struct kvm_vm *vm) { sparsebit_set_num(vm->vpages_valid, |