[PATCH] KVM: arm64: Clarify vcpu reset behaviour

From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Will Deacon <will@kernel.org>,
	kernel-team@android.com, ascull@google.com, tabba@google.com,
	dbrazdil@google.com, James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>
Subject: [PATCH] KVM: arm64: Clarify vcpu reset behaviour
Date: Tue,  6 Apr 2021 13:58:41 +0100	[thread overview]
Message-ID: <20210406125841.1077079-1-maz@kernel.org> (raw)

Although the KVM_ARM_VCPU_INIT documentation mention that the
registers are reset to their "initial values", it doesn't
describe what these values are.

Describe this state explicitly.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 Documentation/virt/kvm/api.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 38e327d4b479..e2237e4e10ba 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -3115,6 +3115,16 @@ optional features it should have.  This will cause a reset of the cpu
 registers to their initial values.  If this is not called, KVM_RUN will
 return ENOEXEC for that vcpu.
 
+The initial values are defined as:
+	- Processor state:
+		* AArch64: EL1h, D, A, I and F bits set
+		* Aarch32: SVC, D, A, I and F bits set
+	- General Purpose registers, including PC and SP: set to 0
+	- FPSIMD/NEON registers: set to 0
+	- SVE registers: set to 0
+	- System registers: Reset to their architecturally defined
+	  values as for a warm reset to EL1 (resp. SVC)
+
 Note that because some registers reflect machine topology, all vcpus
 should be created before this ioctl is invoked.
 
-- 
2.29.2


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