linux-kernel - Re: [PATCH v5 16/16] iommu/hyperv: setup an IO-APIC IRQ remapping domain for root partition

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Date:   Thu, 4 Feb 2021 16:48:35 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     Wei Liu <wei.liu@...nel.org>,
        Linux on Hyper-V List <linux-hyperv@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>,
        Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
        "pasha.tatashin@...een.com" <pasha.tatashin@...een.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH v5 16/16] iommu/hyperv: setup an IO-APIC IRQ remapping
 domain for root partition

On Thu, Feb 04, 2021 at 04:41:47PM +0000, Michael Kelley wrote:
> From: Wei Liu <wei.liu@...nel.org> Sent: Wednesday, February 3, 2021 4:47 AM
[...]
> > > > +
> > > > +	if (level)
> > > > +		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_LEVEL;
> > > > +	else
> > > > +		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_EDGE;
> > > > +
> > > > +	__set_bit(vcpu, (unsigned long *)&intr_desc->target.vp_mask);
> > > > +
> > > > +	status = hv_do_rep_hypercall(HVCALL_MAP_DEVICE_INTERRUPT, 0, 0, input,
> > output) &
> > > > +			 HV_HYPERCALL_RESULT_MASK;
> > > > +	local_irq_restore(flags);
> > > > +
> > > > +	*entry = output->interrupt_entry;
> > > > +
> > > > +	return status;
> > >
> > > As a cross-check, I was comparing this code against hv_map_msi_interrupt().  They are
> > > mostly parallel, though some of the assignments are done in a different order.  It's a nit,
> > > but making them as parallel as possible would be nice. :-)
> > >
> > 
> > Indeed. I will see about factoring out a function.
> 
> If factoring out a separate helper function is clumsy, just having the parallel code
> in the two functions be as similar as possible makes it easier to see what's the
> same and what's different.
> 

No. It is not clumsy at all. I've done it in the newly posted v6.

I was baffled why I wrote hv_unmap_interrupt helper to be used by both
hv_unmap_ioapic_interrupt and hv_unmap_msi_interrupt in the previous
patch, but didn't write a hv_map_interrupt. Maybe I didn't have enough
coffee that day. :-/

Thanks for pointing out that issue. It definitely helped improve the
quality of this series.

Wei.