KVM: arm64: selftests: Align VA space allocator with TTBR0

An interesting feature of the Arm architecture is that the stage-1 MMU
supports two distinct VA regions, controlled by TTBR{0,1}_EL1. As KVM
selftests on arm64 only uses TTBR0_EL1, the VA space is constrained to
[0, 2^(va_bits-1)). This is different from other architectures that
allow for addressing low and high regions of the VA space from a single
page table.

KVM selftests' VA space allocator presumes the valid address range is
split between low and high memory based the MSB, which of course is a
poor match for arm64's TTBR0 region.

Allow architectures to override the default VA space layout. Make use of
the override to align vpages_valid with the behavior of TTBR0 on arm64.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Message-Id: <20221207214809.489070-4-oliver.upton@linux.dev>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/lib/aarch64/processor.c b/tools/testing/selftests/kvm/lib/aarch64/processor.c
index 316de70db91d..5972a23b2765 100644
--- a/tools/testing/selftests/kvm/lib/aarch64/processor.c
+++ b/tools/testing/selftests/kvm/lib/aarch64/processor.c
@@ -541,3 +541,13 @@ void kvm_selftest_arch_init(void)
 	 */
 	guest_modes_append_default();
 }
+
+void vm_vaddr_populate_bitmap(struct kvm_vm *vm)
+{
+	/*
+	 * arm64 selftests use only TTBR0_EL1, meaning that the valid VA space
+	 * is [0, 2^(64 - TCR_EL1.T0SZ)).
+	 */
+	sparsebit_set_num(vm->vpages_valid, 0,
+			  (1ULL << vm->va_bits) >> vm->page_shift);
+}