linux-kernel - [PATCH v1 0/4] A couple of improvements for VMM to inject external abort to guest

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Message-ID: <20250731212004.1437336-1-jiaqiyan@google.com>
Date: Thu, 31 Jul 2025 21:20:00 +0000
From: Jiaqi Yan <jiaqiyan@...gle.com>
To: maz@...nel.org, oliver.upton@...ux.dev
Cc: joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com, 
	catalin.marinas@....com, will@...nel.org, pbonzini@...hat.com, corbet@....net, 
	shuah@...nel.org, kvm@...r.kernel.org, kvmarm@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	rananta@...gle.com, Jiaqi Yan <jiaqiyan@...gle.com>
Subject: [PATCH v1 0/4] A couple of improvements for VMM to inject external
 abort to guest

There are several situations where VMM is involved when handling
synchronous external instruction or data aborts, and often VMM
needs to inject external aborts to guest. In addition to manipulating
individual registers with KVM_SET_ONE_REG API, an easier way is to
use the KVM_SET_VCPU_EVENTS API.

This patchset adds two new features to the KVM_SET_VCPU_EVENTS API.
1. Extend KVM_SET_VCPU_EVENTS to support external instruction abort.
2. Allow userspace to emulate ESR_ELx.ISS by supplying ESR_ELx.
   In this way, we can also allow userspace to emulate ESR_ELx.ISS2
   in future.

The UAPI change for #1 is straightforward. However, I would appreciate
some feedback on the ABI change for #2:

  struct kvm_vcpu_events {
    struct {
        __u8 serror_pending;
        __u8 serror_has_esr;
        __u8 ext_dabt_pending;
        __u8 ext_iabt_pending;
        __u8 ext_abt_has_esr;
        __u8 pad[3];
        __u64 serror_esr;
        __u64 ext_abt_esr;  // <= +8 bytes
      } exception;
    __u32 reserved[10];     // <= -8 bytes
  };

The offset to kvm_vcpu_events.reserved changes, and the size of
exception changes. I think we can't say userspace will never access
reserved, or they will never use sizeof(exception). Theoretically this
is an ABI break and I want to call it out and ask if a new ABI is needed
for feature #2. For example, is it worthy to introduce exception_v2
or kvm_vcpu_events_v2.

Based on commit 7b8346bd9fce6 ("KVM: arm64: Don't attempt vLPI mappings
when vPE allocation is disabled")

Jiaqi Yan (3):
  KVM: arm64: Allow userspace to supply ESR when injecting SEA
  KVM: selftests: Test injecting external abort with ISS
  Documentation: kvm: update UAPI for injecting SEA

Raghavendra Rao Ananta (1):
  KVM: arm64: Allow userspace to inject external instruction abort

 Documentation/virt/kvm/api.rst                |  48 +++--
 arch/arm64/include/asm/kvm_emulate.h          |   9 +-
 arch/arm64/include/uapi/asm/kvm.h             |   7 +-
 arch/arm64/kvm/arm.c                          |   1 +
 arch/arm64/kvm/emulate-nested.c               |   6 +-
 arch/arm64/kvm/guest.c                        |  42 ++--
 arch/arm64/kvm/inject_fault.c                 |  16 +-
 include/uapi/linux/kvm.h                      |   1 +
 tools/arch/arm64/include/uapi/asm/kvm.h       |   7 +-
 .../selftests/kvm/arm64/external_aborts.c     | 191 +++++++++++++++---
 .../testing/selftests/kvm/arm64/inject_iabt.c |  98 +++++++++
 11 files changed, 352 insertions(+), 74 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/arm64/inject_iabt.c

-- 
2.50.1.565.gc32cd1483b-goog