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 (esa5.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=esa5.hc3370-68.iphmx.com;
  envelope-from="sergey.dyasli@citrix.com";
  x-sender="sergey.dyasli@citrix.com";
  x-conformance=sidf_compatible
Received-SPF: Pass (esa5.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=esa5.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"
Received-SPF: None (esa5.hc3370-68.iphmx.com: no sender
  authenticity information available from domain of
  postmaster@mail.citrix.com) identity=helo;
  client-ip=162.221.158.21; receiver=esa5.hc3370-68.iphmx.com;
  envelope-from="sergey.dyasli@citrix.com";
  x-sender="postmaster@mail.citrix.com";
  x-conformance=sidf_compatible
IronPort-SDR: NbCBsYaY7tmZHavhqZHrbPJ2IHI7GEcD1su+OtjP6Feuh7t+T6eFm5iKhfT122oG8TD/O3R8jw
 C5g0kaQf1sgi6i8GcO+rDSWiFdeM6ww+sxchmgZSpu1Ngha9qM0EQzQdNSAaRt8Bu7M5x2Bkbn
 kDUjOTCdTHUFqKjA6qLuOGaJDttPGeQ9ydKYf6zzUacaY7RFxrX6j7R3mqaLyNlRpVq1pDJScF
 Bg8JDVmtoM4n0+LyzPPxNHsH0+1tlVZxNMup64noARhGcmZ/Hao+6WQaKQ8zkTwvKLNKggLICd
 weI=
From:   Sergey Dyasli <sergey.dyasli@citrix.com>
To:     <xen-devel@lists.xen.org>, <kasan-dev@googlegroups.com>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
CC:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.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 <sergey.dyasli@citrix.com>
Subject: [PATCH v3 1/4] kasan: introduce set_pmd_early_shadow()
Date:   Fri, 7 Feb 2020 14:26:49 +0000
Message-ID: <20200207142652.670-2-sergey.dyasli@citrix.com>
In-Reply-To: <20200207142652.670-1-sergey.dyasli@citrix.com>
References: <20200207142652.670-1-sergey.dyasli@citrix.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

It is incorrect to call pmd_populate_kernel() multiple times for the
same page table from inside Xen PV domains. 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>
---
v2 --> v3: no changes

v1 --> v2:
- Fix compilation without CONFIG_XEN_PV
- Slightly updated description

RFC --> v1:
- New patch
---
 mm/kasan/init.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index ce45c491ebcd..7791fe0a7704 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -81,6 +81,26 @@ static inline bool kasan_early_shadow_page_entry(pte_t pte)
 	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
 }
 
+#ifdef CONFIG_XEN_PV
+static inline void set_pmd_early_shadow(pmd_t *pmd)
+{
+	static bool pmd_populated = false;
+	pte_t *early_shadow = lm_alias(kasan_early_shadow_pte);
+
+	if (likely(pmd_populated)) {
+		set_pmd(pmd, __pmd(__pa(early_shadow) | _PAGE_TABLE));
+	} else {
+		pmd_populate_kernel(&init_mm, pmd, early_shadow);
+		pmd_populated = true;
+	}
+}
+#else
+static inline void set_pmd_early_shadow(pmd_t *pmd)
+{
+	pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_early_shadow_pte));
+}
+#endif /* ifdef CONFIG_XEN_PV */
+
 static __init void *early_alloc(size_t size, int node)
 {
 	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
@@ -120,8 +140,7 @@ static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 		next = pmd_addr_end(addr, end);
 
 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
-			pmd_populate_kernel(&init_mm, pmd,
-					lm_alias(kasan_early_shadow_pte));
+			set_pmd_early_shadow(pmd);
 			continue;
 		}
 
@@ -157,8 +176,7 @@ static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
 			pud_populate(&init_mm, pud,
 					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
-			pmd_populate_kernel(&init_mm, pmd,
-					lm_alias(kasan_early_shadow_pte));
+			set_pmd_early_shadow(pmd);
 			continue;
 		}
 
@@ -198,8 +216,7 @@ static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 			pud_populate(&init_mm, pud,
 					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
-			pmd_populate_kernel(&init_mm, pmd,
-					lm_alias(kasan_early_shadow_pte));
+			set_pmd_early_shadow(pmd);
 			continue;
 		}
 
@@ -271,8 +288,7 @@ int __ref kasan_populate_early_shadow(const void *shadow_start,
 			pud_populate(&init_mm, pud,
 					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
-			pmd_populate_kernel(&init_mm, pmd,
-					lm_alias(kasan_early_shadow_pte));
+			set_pmd_early_shadow(pmd);
 			continue;
 		}
 
-- 
2.17.1