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

[Shuo A Liu]

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 <zhi.a.wang@xxxxxxxxx>
> > 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 <zhi.a.wang@xxxxxxxxx>
> > Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
> > Cc: Yu Wang <yu1.wang@xxxxxxxxx>
> > 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)
> >  	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