linux-kernel - Re: [RFC PATCH v2 1/9] KVM: arm64: nv: selftests: Add support to run guest code in vEL2.

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Message-ID: <868qmfeiu4.wl-maz@kernel.org>
Date: Thu, 29 May 2025 12:50:59 +0100
From: Marc Zyngier <maz@...nel.org>
To: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
Cc: linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	oliver.upton@...ux.dev,
	joey.gouly@....com,
	suzuki.poulose@....com,
	yuzenghui@...wei.com,
	seanjc@...gle.com,
	darren@...amperecomputing.com
Subject: Re: [RFC PATCH v2 1/9] KVM: arm64: nv: selftests: Add support to run guest code in vEL2.

On Mon, 12 May 2025 11:52:43 +0100,
Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com> wrote:
> 
> This patch adds required changes to vcpu init to run a guest code
> in vEL2 context and also adds NV specific helper functions.
> 
> Signed-off-by: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
> ---
>  tools/testing/selftests/kvm/Makefile.kvm      |  2 +
>  .../kvm/include/arm64/kvm_util_arch.h         |  3 +
>  .../selftests/kvm/include/arm64/nv_util.h     | 45 ++++++++++++++
>  .../selftests/kvm/include/arm64/vgic.h        |  1 +
>  .../testing/selftests/kvm/include/kvm_util.h  |  3 +
>  tools/testing/selftests/kvm/lib/arm64/nv.c    | 46 ++++++++++++++
>  .../selftests/kvm/lib/arm64/processor.c       | 61 ++++++++++++++-----
>  tools/testing/selftests/kvm/lib/arm64/vgic.c  |  8 +++
>  8 files changed, 155 insertions(+), 14 deletions(-)
>  create mode 100644 tools/testing/selftests/kvm/include/arm64/nv_util.h
>  create mode 100644 tools/testing/selftests/kvm/lib/arm64/nv.c
> 
> diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
> index f773f8f99249..3348f729d3b2 100644
> --- a/tools/testing/selftests/kvm/Makefile.kvm
> +++ b/tools/testing/selftests/kvm/Makefile.kvm
> @@ -37,6 +37,7 @@ LIBKVM_arm64 += lib/arm64/processor.c
>  LIBKVM_arm64 += lib/arm64/spinlock.c
>  LIBKVM_arm64 += lib/arm64/ucall.c
>  LIBKVM_arm64 += lib/arm64/vgic.c
> +LIBKVM_arm64 += lib/arm64/nv.c
>  
>  LIBKVM_s390 += lib/s390/diag318_test_handler.c
>  LIBKVM_s390 += lib/s390/processor.c
> @@ -155,6 +156,7 @@ TEST_GEN_PROGS_arm64 += arm64/vgic_irq
>  TEST_GEN_PROGS_arm64 += arm64/vgic_lpi_stress
>  TEST_GEN_PROGS_arm64 += arm64/vpmu_counter_access
>  TEST_GEN_PROGS_arm64 += arm64/no-vgic-v3
> +TEST_GEN_PROGS_arm64 += arm64/nv_guest_hypervisor
>  TEST_GEN_PROGS_arm64 += access_tracking_perf_test
>  TEST_GEN_PROGS_arm64 += arch_timer
>  TEST_GEN_PROGS_arm64 += coalesced_io_test
> diff --git a/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h b/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h
> index e43a57d99b56..ab5279c24413 100644
> --- a/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h
> +++ b/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h
> @@ -2,6 +2,9 @@
>  #ifndef SELFTEST_KVM_UTIL_ARCH_H
>  #define SELFTEST_KVM_UTIL_ARCH_H
>  
> +#define CurrentEL_EL1		(1 << 2)
> +#define CurrentEL_EL2		(2 << 2)
> +
>  struct kvm_vm_arch {};
>  
>  #endif  // SELFTEST_KVM_UTIL_ARCH_H
> diff --git a/tools/testing/selftests/kvm/include/arm64/nv_util.h b/tools/testing/selftests/kvm/include/arm64/nv_util.h
> new file mode 100644
> index 000000000000..622a17c9d142
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/include/arm64/nv_util.h
> @@ -0,0 +1,45 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2025 Ampere Computing
> + */
> +#ifndef SELFTEST_NV_UTIL_H
> +#define SELFTEST_NV_UTIL_H
> +
> +#include <linux/bitmap.h>
> +#include <vgic.h>
> +
> +#define HCR_NV2		(UL(1) << 45)
> +#define HCR_AT		(UL(1) << 44)
> +#define HCR_NV		(UL(1) << 42)
> +#define HCR_E2H		(UL(1) << 34)
> +#define HCR_TTLB        (UL(1) << 25)
> +
> +/* Enable NV2 and guest in VHE mode */
> +#define HCR_EL2_NV_EANBLE (HCR_E2H | HCR_NV | HCR_NV2 | HCR_AT | HCR_TTLB)
> +

What is the point of enabling NV and trapping all sort of things,
given that you're not even enabling a guest? How do you expect to deal
with EL0 without TGE being set?

	M.

-- 
Without deviation from the norm, progress is not possible.