linux-kernel - Re: [Patch v3 13/14] PCI: hv: Add hypercalls to read/write MMIO space

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Message-ID: <Y3Zoz2VcpXlhlazS@liuwe-devbox-debian-v2>
Date:   Thu, 17 Nov 2022 17:01:03 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
Cc:     Wei Liu <wei.liu@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        KY Srinivasan <kys@...rosoft.com>,
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Subject: Re: [Patch v3 13/14] PCI: hv: Add hypercalls to read/write MMIO space

On Thu, Nov 17, 2022 at 04:14:44PM +0000, Michael Kelley (LINUX) wrote:
> From: Wei Liu <wei.liu@...nel.org> Sent: Thursday, November 17, 2022 7:17 AM
> >
> > On Wed, Nov 16, 2022 at 10:41:36AM -0800, Michael Kelley wrote:
> > [...]
> > >
> > > +static void hv_pci_read_mmio(struct device *dev, phys_addr_t gpa, int size, u32
> > *val)
> > > +{
> > > +	struct hv_mmio_read_input *in;
> > > +	struct hv_mmio_read_output *out;
> > > +	u64 ret;
> > > +
> > > +	/*
> > > +	 * Must be called with interrupts disabled so it is safe
> > > +	 * to use the per-cpu input argument page.  Use it for
> > > +	 * both input and output.
> > > +	 */
> > 
> > Perhaps adding something along this line?
> > 
> > 	WARN_ON(!irqs_disabled());
> > 
> > I can fold this in if you agree.
> 
> These two new functions are only called within this module from code
> that already has interrupts disabled (as added in Patch 14 of the series),
> so I didn't do the extra check.  But I'm OK with adding it.  These functions
> make a hypercall, so the additional check doesn't have enough perf
> impact to matter.

Okay, not adding them is fine too.

Thanks,
Wei.