Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Received-SPF: None (esa1.hc3370-68.iphmx.com: no sender
  authenticity information available from domain of
  sergey.dyasli@citrix.com) identity=pra;
  client-ip=162.221.158.21; receiver=esa1.hc3370-68.iphmx.com;
  envelope-from="sergey.dyasli@citrix.com";
  x-sender="sergey.dyasli@citrix.com";
  x-conformance=sidf_compatible
Received-SPF: Pass (esa1.hc3370-68.iphmx.com: domain of
  sergey.dyasli@citrix.com designates 162.221.158.21 as
  permitted sender) identity=mailfrom;
  client-ip=162.221.158.21; receiver=esa1.hc3370-68.iphmx.com;
  envelope-from="sergey.dyasli@citrix.com";
  x-sender="sergey.dyasli@citrix.com";
  x-conformance=sidf_compatible; x-record-type="v=spf1";
  x-record-text="v=spf1 ip4:209.167.231.154 ip4:178.63.86.133
  ip4:195.66.111.40/30 ip4:85.115.9.32/28 ip4:199.102.83.4
  ip4:192.28.146.160 ip4:192.28.146.107 ip4:216.52.6.88
  ip4:216.52.6.188 ip4:162.221.158.21 ip4:162.221.156.83
  ip4:168.245.78.127 ~all"
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  authenticity information available from domain of
  postmaster@mail.citrix.com) identity=helo;
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  envelope-from="sergey.dyasli@citrix.com";
  x-sender="postmaster@mail.citrix.com";
  x-conformance=sidf_compatible
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 GFg=
Subject: Re: [PATCH v1 1/4] kasan: introduce set_pmd_early_shadow()
To:     Juergen Gross <jgross@suse.com>
CC:     <xen-devel@lists.xen.org>, <kasan-dev@googlegroups.com>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        "Dmitry Vyukov" <dvyukov@google.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        George Dunlap <george.dunlap@citrix.com>,
        Ross Lagerwall <ross.lagerwall@citrix.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "sergey.dyasli@citrix.com >> Sergey Dyasli" 
        <sergey.dyasli@citrix.com>
References: <20200108152100.7630-1-sergey.dyasli@citrix.com>
 <20200108152100.7630-2-sergey.dyasli@citrix.com>
From:   Sergey Dyasli <sergey.dyasli@citrix.com>
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Message-ID: <96c2414e-91fb-5a28-44bc-e30d2daabec5@citrix.com>
Date:   Wed, 15 Jan 2020 10:54:45 +0000
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In-Reply-To: <20200108152100.7630-2-sergey.dyasli@citrix.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Juergen,

On 08/01/2020 15:20, Sergey Dyasli wrote:
> It is incorrect to call pmd_populate_kernel() multiple times for the
> same page table. Xen notices it during kasan_populate_early_shadow():
>
>     (XEN) mm.c:3222:d155v0 mfn 3704b already pinned
>
> This happens for kasan_early_shadow_pte when USE_SPLIT_PTE_PTLOCKS is
> enabled. Fix this by introducing set_pmd_early_shadow() which calls
> pmd_populate_kernel() only once and uses set_pmd() afterwards.
>
> Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>

Looks like the plan to use set_pmd() directly has failed: it's an
arch-specific function and can't be used in arch-independent code
(as kbuild test robot has proven).

Do you see any way out of this other than disabling SPLIT_PTE_PTLOCKS
for PV KASAN?

--
Thanks,
Sergey