KVM selftests map all guest code and data into the lower virtual address range (0x0000...) managed by TTBR0_EL1. The upper range (0xFFFF...) managed by TTBR1_EL1 is unused and uninitialized. If a guest accesses the upper range, the MMU attempts a translation table walk using uninitialized registers, leading to unpredictable behavior. Set `TCR_EL1.EPD1` to disable translation table walks for TTBR1_EL1, ensuring that any access to the upper range generates an immediate Translation Fault. Additionally, set `TCR_EL1.TBI1` (Top Byte Ignore) to ensure that tagged pointers in the upper range also deterministically trigger a Translation Fault via EPD1. Define `TCR_EPD1_MASK`, `TCR_EPD1_SHIFT`, and `TCR_TBI1` in `processor.h` to support this configuration. These are based on their definitions in `arch/arm64/include/asm/pgtable-hwdef.h`. Suggested-by: Will Deacon Signed-off-by: Fuad Tabba --- tools/testing/selftests/kvm/include/arm64/processor.h | 4 ++++ tools/testing/selftests/kvm/lib/arm64/processor.c | 2 ++ 2 files changed, 6 insertions(+) diff --git a/tools/testing/selftests/kvm/include/arm64/processor.h b/tools/testing/selftests/kvm/include/arm64/processor.h index ff928716574d..ac97a1c436fc 100644 --- a/tools/testing/selftests/kvm/include/arm64/processor.h +++ b/tools/testing/selftests/kvm/include/arm64/processor.h @@ -90,6 +90,9 @@ #define TCR_TG0_64K (UL(1) << TCR_TG0_SHIFT) #define TCR_TG0_16K (UL(2) << TCR_TG0_SHIFT) +#define TCR_EPD1_SHIFT 23 +#define TCR_EPD1_MASK (UL(1) << TCR_EPD1_SHIFT) + #define TCR_IPS_SHIFT 32 #define TCR_IPS_MASK (UL(7) << TCR_IPS_SHIFT) #define TCR_IPS_52_BITS (UL(6) << TCR_IPS_SHIFT) @@ -97,6 +100,7 @@ #define TCR_IPS_40_BITS (UL(2) << TCR_IPS_SHIFT) #define TCR_IPS_36_BITS (UL(1) << TCR_IPS_SHIFT) +#define TCR_TBI1 (UL(1) << 38) #define TCR_HA (UL(1) << 39) #define TCR_DS (UL(1) << 59) diff --git a/tools/testing/selftests/kvm/lib/arm64/processor.c b/tools/testing/selftests/kvm/lib/arm64/processor.c index d46e4b13b92c..5b379da8cb90 100644 --- a/tools/testing/selftests/kvm/lib/arm64/processor.c +++ b/tools/testing/selftests/kvm/lib/arm64/processor.c @@ -384,6 +384,8 @@ void aarch64_vcpu_setup(struct kvm_vcpu *vcpu, struct kvm_vcpu_init *init) tcr_el1 |= TCR_IRGN0_WBWA | TCR_ORGN0_WBWA | TCR_SH0_INNER; tcr_el1 |= TCR_T0SZ(vm->va_bits); + tcr_el1 |= TCR_TBI1; + tcr_el1 |= TCR_EPD1_MASK; if (use_lpa2_pte_format(vm)) tcr_el1 |= TCR_DS; -- 2.52.0.239.gd5f0c6e74e-goog