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From:   Michael Kelley <mikelley@microsoft.com>
To:     Sunil Muthuswamy <sunilmut@microsoft.com>
CC:     "will@kernel.org" <will@kernel.org>,
        "catalin.marinas@arm.com" <catalin.marinas@arm.com>,
        Mark Rutland <Mark.Rutland@arm.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
        "arnd@arndb.de" <arnd@arndb.de>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        "ardb@kernel.org" <ardb@kernel.org>,
        "daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
        KY Srinivasan <kys@microsoft.com>
Subject: RE: [PATCH v8 1/6] arm64: hyperv: Add Hyper-V hypercall and register
 access utilities
Thread-Topic: [PATCH v8 1/6] arm64: hyperv: Add Hyper-V hypercall and register
 access utilities
Thread-Index: AQHXDwVm7IanFUbz6UeLdWLFekPIfapxZzMggAEuN+CAA1B6YA==
Date:   Fri, 5 Mar 2021 20:58:37 +0000
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From: Sunil Muthuswamy <sunilmut@microsoft.com> Sent: Wednesday, March 3, 2=
021 10:28 AM
>=20
> > > +
> > > +	/*
> > > +	 * 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 =3D kzalloc(roundup_pow_of_two(sizeof(input->header) +
> > > +				sizeof(input->element[0])), GFP_ATOMIC);
> > > +	output =3D kmalloc(roundup_pow_of_two(sizeof(*output)), GFP_ATOMIC)=
;
> > > +
> > Check for null from these malloc routines? Here and in other places.
>=20
> Between, is there a plan to setup a percpu input/output page for hypercal=
l
> input/output on ARM (like we do for x64)? I didn't check the specific siz=
e requirement
> for this particular call, but, that generally will remove the need for th=
ese
> allocations.

I'm not planning to add percpu input/output pages in this patch set.  As no=
ted
in another reply, we can eliminate these memory allocations entirely by usi=
ng
"fast" hypercalls.  At that point, there would be no usage of percpu input/=
output
pages in this patch set.  If the need arises in the context of future work,=
 we can
add them at that time.

Michael