linux-kernel - Re: [PATCH v10 18/19] KVM: s390: pv: avoid export before import if possible

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Date:   Mon, 30 May 2022 13:16:52 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     Nico Boehr <nrb@...ux.ibm.com>
Cc:     kvm@...r.kernel.org, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, david@...hat.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        scgl@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v10 18/19] KVM: s390: pv: avoid export before import if
 possible

On Mon, 30 May 2022 12:07:43 +0200
Nico Boehr <nrb@...ux.ibm.com> wrote:

> On Thu, 2022-04-14 at 10:03 +0200, Claudio Imbrenda wrote:
> 
> > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> > index e358b8bd864b..43393568f844 100644
> > --- a/arch/s390/kernel/uv.c
> > +++ b/arch/s390/kernel/uv.c
> > @@ -236,7 +236,8 @@ static int make_secure_pte(pte_t *ptep, unsigned
> > long addr,
> >  
> >  static bool should_export_before_import(struct uv_cb_header *uvcb,
> > struct mm_struct *mm)
> >  {
> > -       return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
> > +       return !test_bit_inv(BIT_UV_FEAT_MISC,
> > &uv_info.uv_feature_indications) &&
> > +               uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
> >                 atomic_read(&mm->context.protected_count) > 1;  
> 
> This might be nicer to read like this:
> 
> if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications))
>   return false;
> 
> if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED)
>   return false;
> 
> return atomic_read(&mm->context.protected_count) > 1;

fair enough

then I'll also fix patch 6 in a similar way, the function is first
introduced there