linux-kernel - [PATCH v1 4/4] Documentation: kvm: update UAPI for injecting SEA

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Message-ID: <20250731212004.1437336-5-jiaqiyan@google.com>
Date: Thu, 31 Jul 2025 21:20:04 +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 4/4] Documentation: kvm: update UAPI for injecting SEA

- KVM_CAP_ARM_INJECT_EXT_IABT: userspace can inject external
  instruction abort to guest.
- ext_abt_has_esr and ext_abt_esr: userspace can supplement ISS
  fields while injecting SEA, for both data and instruction aborts.

Signed-off-by: Jiaqi Yan <jiaqiyan@...gle.com>
---
 Documentation/virt/kvm/api.rst | 48 +++++++++++++++++++++++++---------
 1 file changed, 36 insertions(+), 12 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 53e0179d52949..8190ffb145c37 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1236,9 +1236,11 @@ directly to the virtual CPU).
 		__u8 serror_pending;
 		__u8 serror_has_esr;
 		__u8 ext_dabt_pending;
+		__u8 ext_iabt_pending;
 		/* Align it to 8 bytes */
-		__u8 pad[5];
+		__u8 pad[4];
 		__u64 serror_esr;
+		__u64 ext_abt_esr;
 	} exception;
 	__u32 reserved[12];
   };
@@ -1292,20 +1294,42 @@ ARM64:
 
 User space may need to inject several types of events to the guest.
 
+Inject SError
+~~~~~~~~~~~~~
+
 Set the pending SError exception state for this VCPU. It is not possible to
 'cancel' an Serror that has been made pending.
 
-If the guest performed an access to I/O memory which could not be handled by
-userspace, for example because of missing instruction syndrome decode
-information or because there is no device mapped at the accessed IPA, then
-userspace can ask the kernel to inject an external abort using the address
-from the exiting fault on the VCPU. It is a programming error to set
-ext_dabt_pending after an exit which was not either KVM_EXIT_MMIO or
-KVM_EXIT_ARM_NISV. This feature is only available if the system supports
-KVM_CAP_ARM_INJECT_EXT_DABT. This is a helper which provides commonality in
-how userspace reports accesses for the above cases to guests, across different
-userspace implementations. Nevertheless, userspace can still emulate all Arm
-exceptions by manipulating individual registers using the KVM_SET_ONE_REG API.
+Inject SEA (synchronous external abort)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- If the guest performed an access to I/O memory which could not be handled by
+  userspace, for example because of missing instruction syndrome decode
+  information or because there is no device mapped at the accessed IPA.
+
+- If the guest consumed an uncorrectable memory error on guest owned memory,
+  and RAS in the Trusted Firmware chooses to notify PE with SEA, KVM has to
+  handle it when host APEI is unable to claim the SEA. If userspace has enabled
+  KVM_CAP_ARM_SEA_TO_USER, KVM returns to userspace with KVM_EXIT_ARM_SEA.
+
+For the cases above, userspace can ask the kernel to replay either an external
+data abort (by setting ext_dabt_pending) or an external instruction abort
+(by setting ext_iabt_pending) into the faulting VCPU. Userspace can provide
+Instruction Specific Syndrome (ISS) in the ext_abt_esr field to supplement
+the ESR register value being injected into the faulting VCPU. KVM will use the
+address from the existing fault on the VCPU. Setting both ext_dabt_pending and
+ext_iabt_pending at the same time will return -EINVAL. Setting anything not
+being part of the ISS (bits [24:0] of ext_abt_esr) will return -EINVAL.
+
+It is a programming error to set ext_dabt_pending or ext_iabt_pending after an
+exit which was not KVM_EXIT_MMIO, KVM_EXIT_ARM_NISV or KVM_EXIT_ARM_SEA.
+Injecting SEA for data and instruction abort is only available if KVM supports
+KVM_CAP_ARM_INJECT_EXT_DABT and KVM_CAP_ARM_INJECT_EXT_IABT respectively.
+
+This is a helper which provides commonality in how userspace reports accesses
+for the above cases to guests, across different userspace implementations.
+Nevertheless, userspace can still emulate all Arm exceptions by manipulating
+individual registers using the KVM_SET_ONE_REG API.
 
 See KVM_GET_VCPU_EVENTS for the data structure.
 
-- 
2.50.1.565.gc32cd1483b-goog