From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH 3/3] xen: arm: correctly handle removing a subset of a superpage mapping. Date: Mon, 14 Jul 2014 19:34:08 +0100 Message-ID: <53C422A0.5070405@linaro.org> References: <1405355194.31863.2.camel@kazak.uk.xensource.com> <1405355225-4623-3-git-send-email-ian.campbell@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1405355225-4623-3-git-send-email-ian.campbell@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell , xen-devel@lists.xen.org Cc: tim@xen.org, stefano.stabellini@eu.citrix.com List-Id: xen-devel@lists.xenproject.org Hi Ian, On 07/14/2014 05:27 PM, Ian Campbell wrote: > This can be exercised for example via ballooning which will remove 4K > regions fromanywhere in the address space. Missing space between "from" and "anywhere" > > Reported-by: Julien Grall > Signed-off-by: Ian Campbell > --- > xen/arch/arm/p2m.c | 29 +++++++++++++++++++++++++++-- > 1 file changed, 27 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c > index a10cbaf..68a19bd 100644 > --- a/xen/arch/arm/p2m.c > +++ b/xen/arch/arm/p2m.c > @@ -604,8 +604,33 @@ static int apply_one_level(struct domain *d, > return P2M_ONE_PROGRESS_NOP; > } > > - if ( level < 3 && p2m_table(orig_pte) ) > - return P2M_ONE_DESCEND; > + if ( level < 3 ) > + { > + if ( p2m_table(orig_pte) ) > + return P2M_ONE_DESCEND; > + > + if ( op == REMOVE && > + !is_mapping_aligned(*addr, end_gpaddr, > + 0, /* maddr doesn't matter for remove */ > + level_size) ) > + { > + /* > + * Removing a mapping from the middle of a superpage. Shatter > + * and descend. > + */ > + *flush = true; > + rc = p2m_create_table(d, entry, > + level_shift - PAGE_SHIFT, flush_cache); > + if ( rc < 0 ) > + return rc; > + > + p2m->stats.shattered[level]++; > + p2m->stats.mappings[level]--; > + p2m->stats.mappings[level+1] += LPAE_ENTRIES; > + > + return P2M_ONE_DESCEND; > + } > + } I would put the code below (which is only for level3) in the else part. This will also remove now useless "if ( level == 3 )". > *flush = true; > > Regards, -- Julien Grall