Re: [PATCH v3 02/17] x86/acrn: Introduce acrn_{setup, remove}_intr_handler()

From: Shuo A Liu
Date: Thu Sep 10 2020 - 02:30:47 EST

Hi Greg,

On Wed 9.Sep'20 at 11:36:09 +0200, Greg Kroah-Hartman wrote:
On Wed, Sep 09, 2020 at 05:08:21PM +0800, shuo.a.liu@xxxxxxxxx wrote:
From: Shuo Liu <shuo.a.liu@xxxxxxxxx>

The ACRN Hypervisor builds an I/O request when a trapped I/O access
happens in User VM. Then, ACRN Hypervisor issues an upcall by sending
a notification interrupt to the Service VM. HSM in the Service VM needs
to hook the notification interrupt to handle I/O requests.

Notification interrupts from ACRN Hypervisor are already supported and
a, currently uninitialized, callback called.

Export two APIs for HSM to setup/remove its callback.

Originally-by: Yakui Zhao <yakui.zhao@xxxxxxxxx>
Signed-off-by: Shuo Liu <shuo.a.liu@xxxxxxxxx>
Reviewed-by: Zhi Wang <>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Fengwei Yin <fengwei.yin@xxxxxxxxx>
Cc: Zhi Wang <>
Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
Cc: Yu Wang <>
Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
arch/x86/include/asm/acrn.h | 8 ++++++++
arch/x86/kernel/cpu/acrn.c | 19 +++++++++++++++++++
2 files changed, 27 insertions(+)
create mode 100644 arch/x86/include/asm/acrn.h

diff --git a/arch/x86/include/asm/acrn.h b/arch/x86/include/asm/acrn.h
new file mode 100644
index 000000000000..ff259b69cde7
--- /dev/null
+++ b/arch/x86/include/asm/acrn.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_ACRN_H
+#define _ASM_X86_ACRN_H
+void acrn_setup_intr_handler(void (*handler)(void));
+void acrn_remove_intr_handler(void);
+#endif /* _ASM_X86_ACRN_H */
diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index 0b2c03943ac6..bd1d7e759a0f 100644
--- a/arch/x86/kernel/cpu/acrn.c
+++ b/arch/x86/kernel/cpu/acrn.c
@@ -9,7 +9,11 @@

+#define pr_fmt(fmt) "acrn: " fmt
#include <linux/interrupt.h>
+#include <asm/acrn.h>
#include <asm/apic.h>
#include <asm/cpufeatures.h>
#include <asm/desc.h>
@@ -55,6 +59,21 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_acrn_hv_callback)

+void acrn_setup_intr_handler(void (*handler)(void))
+ if (acrn_intr_handler)
+ pr_warn("Overwrite the acrn_intr_handler.\n");

What can someone do with this warning? If it's really an "error", why
not prevent this from happening?

It cannot happen if there are not new user of it. The current user is
HSM hsm_init()/hsm_exit() in the later patches of this series.

I can remove the warn.

Don't scare users with things they can do nothing about.

OK. Got it. Thanks.