linux-kernel - RE: [PATCH v8 1/6] arm64: hyperv: Add Hyper-V hypercall and register access utilities

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Date:   Wed, 3 Mar 2021 18:28:16 +0000
From:   Sunil Muthuswamy <sunilmut@...rosoft.com>
To:     Sunil Muthuswamy <sunilmut@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>
CC:     "will@...nel.org" <will@...nel.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        Mark Rutland <Mark.Rutland@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "ardb@...nel.org" <ardb@...nel.org>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        KY Srinivasan <kys@...rosoft.com>
Subject: RE: [PATCH v8 1/6] arm64: hyperv: Add Hyper-V hypercall and register
 access utilities

> > +
> > +	/*
> > +	 * Allocate a power of 2 size so alignment to that size is
> > +	 * guaranteed, since the hypercall input and output areas
> > +	 * must not cross a page boundary.
> > +	 */
> > +	input = kzalloc(roundup_pow_of_two(sizeof(input->header) +
> > +				sizeof(input->element[0])), GFP_ATOMIC);
> > +	output = kmalloc(roundup_pow_of_two(sizeof(*output)), GFP_ATOMIC);
> > +
> Check for null from these malloc routines? Here and in other places.

Between, is there a plan to setup a percpu input/output page for hypercall
input/output on ARM (like we do for x64)? I didn't check the specific size requirement
for this particular call, but, that generally will remove the need for these
allocations.