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Date:   Mon, 16 May 2022 18:11:34 +0200
From:   Claudio Imbrenda <imbrenda@linux.ibm.com>
To:     Nico Boehr <nrb@linux.ibm.com>
Cc:     kvm@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com,
        thuth@redhat.com, pasic@linux.ibm.com, david@redhat.com,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        scgl@linux.ibm.com, mimu@linux.ibm.com
Subject: Re: [PATCH v10 04/19] KVM: s390: pv: refactor s390_reset_acc
Message-ID: <20220516181134.40652725@p-imbrenda>
In-Reply-To: <6948806da404fd5822b59fd65b8a5a948e6bb317.camel@linux.ibm.com>
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        <20220414080311.1084834-5-imbrenda@linux.ibm.com>
        <6948806da404fd5822b59fd65b8a5a948e6bb317.camel@linux.ibm.com>
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On Mon, 16 May 2022 10:04:54 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:

> On Thu, 2022-04-14 at 10:02 +0200, Claudio Imbrenda wrote:
> > Refactor s390_reset_acc so that it can be reused in upcoming patches.
> >=20
> > We don't want to hold all the locks used in a walk_page_range for too
> > long, and the destroy page UVC does take some time to complete.
> > Therefore we quickly gather the pages to destroy, and then destroy
> > them
> > without holding all the locks.
> >=20
> > The new refactored function optionally allows to return early without
> > completing if a fatal signal is pending (and return and appropriate
> > error code). Two wrappers are provided to call the new function.
> >=20
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > Reviewed-by: Janosch Frank <frankja@linux.ibm.com> =20
>=20
> Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
>=20
> But see below with one naming suggestion you might want to take into
> account.
>=20
> [...]
> > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> > index e8904cb9dc38..a3a1f90f6ec1 100644
> > --- a/arch/s390/mm/gmap.c
> > +++ b/arch/s390/mm/gmap.c
> > @@ -2676,44 +2676,81 @@ void s390_reset_cmma(struct mm_struct *mm)
> > =C2=A0}
> > =C2=A0EXPORT_SYMBOL_GPL(s390_reset_cmma);
> > =C2=A0
> > -/*
> > - * make inaccessible pages accessible again
> > - */
> > -static int __s390_reset_acc(pte_t *ptep, unsigned long addr,
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0 unsigned long next, struct mm_walk *walk)
> > +#define DESTROY_LOOP_THRESHOLD 32 =20
>=20
> maybe GATHER_NUM_PAGE_REFS_TO_TAKE?

what about GATHER_GET_PAGES ?