On 07/11/2022 17:58, Punit Agrawal wrote:

Usama Arif [off-list ref] writes:

quoted

Add a new SMCCC compatible hypercalls for PV lock features:
   ARM_SMCCC_KVM_FUNC_PV_LOCK:   0xC6000002

Also add the header file which defines the ABI for the paravirtualized
lock features we're about to add.

Signed-off-by: Zengruan Ye <redacted>
Signed-off-by: Usama Arif <redacted>
---
  arch/arm64/include/asm/pvlock-abi.h | 17 +++++++++++++++++
  include/linux/arm-smccc.h           |  8 ++++++++
  tools/include/linux/arm-smccc.h     |  8 ++++++++
  3 files changed, 33 insertions(+)
  create mode 100644 arch/arm64/include/asm/pvlock-abi.h

diff --git a/arch/arm64/include/asm/pvlock-abi.h b/arch/arm64/include/asm/pvlock-abi.h
new file mode 100644
index 000000000000..3f4574071679
--- /dev/null
+++ b/arch/arm64/include/asm/pvlock-abi.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright(c) 2019 Huawei Technologies Co., Ltd
+ * Author: Zengruan Ye <yezengruan@huawei.com>
+ *         Usama Arif <usama.arif@bytedance.com>
+ */
+
+#ifndef __ASM_PVLOCK_ABI_H
+#define __ASM_PVLOCK_ABI_H
+
+struct pvlock_vcpu_state {
+	__le64 preempted;
+	/* Structure must be 64 byte aligned, pad to that size */
+	u8 padding[56];
+} __packed;

For structure alignment, I'd have expected to see the use of "aligned"
attribute. Is there any benefit in using padding to achieve alignment?

Just made it consistent with pvclock-abi.h. If its more appropriate, can 
change to aligned in next patchset:

diff --git a/arch/arm64/include/asm/pvlock-abi.h 

b/arch/arm64/include/asm/pvlock-abi.h
index 3f4574071679..bacec4cb927a 100644

--- a/arch/arm64/include/asm/pvlock-abi.h
+++ b/arch/arm64/include/asm/pvlock-abi.h

@@ -11,7 +11,6 @@
  struct pvlock_vcpu_state {
         __le64 preempted;
         /* Structure must be 64 byte aligned, pad to that size */
-       u8 padding[56];
-} __packed;
+} __attribute__((aligned(64)));

[...]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel