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Date:   Thu, 10 Sep 2020 14:30:32 +0800
From:   Shuo A Liu <shuo.a.liu@intel.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Yu Wang <yu1.wang@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Yakui Zhao <yakui.zhao@intel.com>,
        Zhi Wang <zhi.a.wang@intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Fengwei Yin <fengwei.yin@intel.com>,
        Zhenyu Wang <zhenyuw@linux.intel.com>
Subject: Re: [PATCH v3 02/17] x86/acrn: Introduce acrn_{setup,
 remove}_intr_handler()
Message-ID: <20200910063032.GJ13723@shuo-intel.sh.intel.com>
References: <20200909090836.46762-1-shuo.a.liu@intel.com>
 <20200909090836.46762-3-shuo.a.liu@intel.com>
 <20200909093609.GA607744@kroah.com>
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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@intel.com wrote:
>> From: Shuo Liu <shuo.a.liu@intel.com>
>>
>> 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@intel.com>
>> Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
>> Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
>> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
>> Cc: Dan Williams <dan.j.williams@intel.com>
>> Cc: Fengwei Yin <fengwei.yin@intel.com>
>> Cc: Zhi Wang <zhi.a.wang@intel.com>
>> Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
>> Cc: Yu Wang <yu1.wang@intel.com>
>> Cc: Reinette Chatre <reinette.chatre@intel.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> ---
>>  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)
>>  	set_irq_regs(old_regs);
>>  }
>>
>> +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.

Thanks
shuo