From: Wei Liu <wei.liu2@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: KevinTian <kevin.tian@intel.com>, Wei Liu <wei.liu2@citrix.com>,
suravee.suthikulpanit@amd.com,
AndrewCooper <andrew.cooper3@citrix.com>,
EddieDong <eddie.dong@intel.com>,
Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>,
Jun Nakajima <jun.nakajima@intel.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Keir Fraser <keir@xen.org>
Subject: Re: [PATCH] x86/HVM: honor p2m_ram_ro in hvm_map_guest_frame_rw()
Date: Fri, 24 Jul 2015 11:41:09 +0100 [thread overview]
Message-ID: <20150724104109.GC30594@zion.uk.xensource.com> (raw)
In-Reply-To: <55B231850200007800095110@prv-mh.provo.novell.com>
On Fri, Jul 24, 2015 at 04:37:25AM -0600, Jan Beulich wrote:
> >>> On 24.07.15 at 12:26, <wei.liu2@citrix.com> wrote:
> > On Fri, Jul 24, 2015 at 03:41:26AM -0600, Jan Beulich wrote:
> >> @@ -3618,7 +3618,12 @@ static void *__hvm_map_guest_frame(unsig
> >> }
> >>
> >> if ( writable )
> >
> > I don't claim I know this piece of code, but checking the pointer but
> > not the content looks suspicious.
> >
> >> - paging_mark_dirty(d, page_to_mfn(page));
> >> + {
> >> + if ( !p2m_is_discard_write(p2mt) )
> >> + paging_mark_dirty(d, page_to_mfn(page));
> >> + else
> >> + *writable = 0;
> >
> > You then set *writable here, which makes it even more suspicious.
>
> Why? A caller _wanting_ a writable mapping passes non-NULL as
> the pointer argument (pre-initialized to point to a variable holding
> TRUE aka 1). Upon return the variable will have got set to FALSE
> aka 0 if the page shouldn't be written to.
>
If this is the convention for using this function then the code you
write is of course fine.
Wei.
> Jan
next prev parent reply other threads:[~2015-07-24 10:41 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-24 9:41 [PATCH] x86/HVM: honor p2m_ram_ro in hvm_map_guest_frame_rw() Jan Beulich
2015-07-24 10:26 ` Wei Liu
2015-07-24 10:37 ` Jan Beulich
2015-07-24 10:41 ` Wei Liu [this message]
2015-07-24 12:02 ` Andrew Cooper
2015-07-24 12:33 ` Jan Beulich
2015-07-27 11:09 ` Tim Deegan
2015-08-11 13:51 ` Jan Beulich
2015-08-11 14:34 ` Tim Deegan
2015-08-11 15:37 ` Jan Beulich
2015-08-11 15:45 ` Tim Deegan
2015-08-11 16:01 ` Jan Beulich
2015-07-31 1:41 ` Tian, Kevin
2015-07-31 16:06 ` Boris Ostrovsky
2015-08-11 10:32 ` Jan Beulich
2015-08-14 10:38 ` Jan Beulich
2015-08-14 13:26 ` Boris Ostrovsky
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