Re: [Xen-devel] [PATCH v8 1/5] x86/p2m: Allow p2m_get_page_from_gfn to return shared entries

From: Tamas K Lengyel <tamas.k.lengyel@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Tamas K Lengyel" <tamas.lengyel@intel.com>,
	"Wei Liu" <wl@xen.org>,
	"George Dunlap" <george.dunlap@eu.citrix.com>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	Xen-devel <xen-devel@lists.xenproject.org>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v8 1/5] x86/p2m: Allow p2m_get_page_from_gfn to return shared entries
Date: Tue, 11 Feb 2020 06:34:21 -0700	[thread overview]
Message-ID: <CABfawh=uq2Yt0XsLdEM=C1vKBH0+vzki7n1OOjZecuaHOTL3SQ@mail.gmail.com> (raw)
In-Reply-To: <6be1e66b-9c0b-9dc6-2062-dda74ad2ccc8@suse.com>

On Tue, Feb 11, 2020 at 4:04 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 11.02.2020 11:29, Tamas K Lengyel wrote:
> > On Tue, Feb 11, 2020 at 2:17 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> On 10.02.2020 20:21, Tamas K Lengyel wrote:
> >>> The owner domain of shared pages is dom_cow, use that for get_page
> >>> otherwise the function fails to return the correct page under some
> >>> situations. The check if dom_cow should be used was only performed in
> >>> a subset of use-cases. Fixing the error and simplifying the existing check
> >>> since we can't have any shared entries with dom_cow being NULL.
> >>>
> >>> Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
> >>
> >> I find it quite disappointing that the blank lines requested to be
> >> added ...
> >>
> >>> --- a/xen/arch/x86/mm/p2m.c
> >>> +++ b/xen/arch/x86/mm/p2m.c
> >>> @@ -574,11 +574,12 @@ struct page_info *p2m_get_page_from_gfn(
> >>>                  if ( fdom == NULL )
> >>>                      page = NULL;
> >>>              }
> >>> -            else if ( !get_page(page, p2m->domain) &&
> >>> -                      /* Page could be shared */
> >>> -                      (!dom_cow || !p2m_is_shared(*t) ||
> >>> -                       !get_page(page, dom_cow)) )
> >>> -                page = NULL;
> >>> +            else
> >>> +            {
> >>> +                struct domain *d = !p2m_is_shared(*t) ? p2m->domain : dom_cow;
> >>> +                if ( !get_page(page, d) )
> >>
> >> .. above here and ...
> >>
> >>> @@ -594,8 +595,9 @@ struct page_info *p2m_get_page_from_gfn(
> >>>      mfn = get_gfn_type_access(p2m, gfn_x(gfn), t, a, q, NULL);
> >>>      if ( p2m_is_ram(*t) && mfn_valid(mfn) )
> >>>      {
> >>> +        struct domain *d = !p2m_is_shared(*t) ? p2m->domain : dom_cow;
> >>>          page = mfn_to_page(mfn);
> >>
> >> ... above here still haven't appeared. No matter that it's easy to
> >> do so while committing, when you send a new version you should
> >> really address such remarks yourself, I think.
> >
> > Noted. I haven't addressed it since it appeared to me that this patch
> > has been ready to go in for like 3 revisions already as-is given the
> > blank-lines were non-blockers.
>
> The patch continues to lack a maintainer ack. Hence it hasn't been
> ready to go in at any point in time.

I meant there has been no comments or anything blocking noted for
three resends now.

Tamas

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