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d="scan'208";a="10950738" Subject: Re: [PATCH v1 1/4] kasan: introduce set_pmd_early_shadow() To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= CC: , , , , Andrey Ryabinin , Alexander Potapenko , "Dmitry Vyukov" , Boris Ostrovsky , Stefano Stabellini , George Dunlap , Ross Lagerwall , Andrew Morton , "sergey.dyasli@citrix.com >> Sergey Dyasli" References: <20200108152100.7630-1-sergey.dyasli@citrix.com> <20200108152100.7630-2-sergey.dyasli@citrix.com> <96c2414e-91fb-5a28-44bc-e30d2daabec5@citrix.com> <6f643816-a7dc-f3bb-d521-b6ac104918d6@suse.com> From: Sergey Dyasli Autocrypt: addr=sergey.dyasli@citrix.com; keydata= xsFNBFtMVHEBEADc/hZcLexrB6vGTdGqEUsYZkFGQh6Z1OO7bCtM1go1RugSMeq9tkFHQSOc 9c7W9NVQqLgn8eefikIHxgic6tGgKoIQKcPuSsnqGao2YabsTSSoeatvmO5HkR0xGaUd+M6j iqv3cD7/WL602NhphT4ucKXCz93w0TeoJ3gleLuILxmzg1gDhKtMdkZv6TngWpKgIMRfoyHQ jsVzPbTTjJl/a9Cw99vuhFuEJfzbLA80hCwhoPM+ZQGFDcG4c25GQGQFFatpbQUhNirWW5b1 r2yVOziSJsvfTLnyzEizCvU+r/Ek2Kh0eAsRFr35m2X+X3CfxKrZcePxzAf273p4nc3YIK9h cwa4ZpDksun0E2l0pIxg/pPBXTNbH+OX1I+BfWDZWlPiPxgkiKdgYPS2qv53dJ+k9x6HkuCy i61IcjXRtVgL5nPGakyOFQ+07S4HIJlw98a6NrptWOFkxDt38x87mSM7aSWp1kjyGqQTGoKB VEx5BdRS5gFdYGCQFc8KVGEWPPGdeYx9Pj2wTaweKV0qZT69lmf/P5149Pc81SRhuc0hUX9K DnYBa1iSHaDjifMsNXKzj8Y8zVm+J6DZo/D10IUxMuExvbPa/8nsertWxoDSbWcF1cyvZp9X tUEukuPoTKO4Vzg7xVNj9pbK9GPxSYcafJUgDeKEIlkn3iVIPwARAQABzShTZXJnZXkgRHlh c2xpIDxzZXJnZXkuZHlhc2xpQGNpdHJpeC5jb20+wsGlBBMBCgA4FiEEkI7HMI5EbM2FLA1L Aa+w5JvbyusFAltMVHECGwMFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AAIQkQAa+w5JvbyusW IQSQjscwjkRszYUsDUsBr7Dkm9vK65AkEACvL+hErqbQj5yTVNqvP1rVGsXvevViglSTkHD4 9LGwEk4+ne8N4DPcqrDnyqYFd42UxTjVyoDEXEIIoy0RHWCmaspYEDX8fVmgFG3OFoeA9NAv JHssHU6B2mDAQ6M3VDmAwTw+TbXL/c1wblgGAP9kdurydZL8bevTTUh7edfnm5pwaT9HLXvl xLjz5qyt6tKEowM0xPVzCKaj3Mf/cuZFOlaWiHZ0biOPC0JeoHuz4UQTnBBUKk+n2nnn72k9 37cNeaxARwn/bxcej9QlbrrdaNGVFzjCA/CIL0KjUepowpLN0+lmYjkPgeLNYfyMXumlSNag 9qnCTh0QDsCXS/HUHPeBskAvwNpGBCkfiP/XqJ+V618ZQ1sclHa9aWNnlIR/a8xVx25t/14V R8EX/045HUpyPU8hI/yw+Fw/ugJ8W0dFzFeHU5K2tEW2W0m3ZWWWgpcBSCB17DDLIPjGX1Qc J8jiVJ7E4rfvA1JBg9BxVw5LVuXg2FB6bqnDYALfY2ydATk+ZzMUAMMilaE7/5a2RMV4TYcd 8Cf77LdgO0pB3vF6z1QmNA2IbOICtJOXpmvHj+dKFUt5hFVbvqXbuAjlrwFktbAFVGxaeIYz nQ44lQu9JqDuSH5yOytdek24Dit8SgEHGvumyj17liCG6kNzxd+2xh3uaUCA5MIALy5mZ87B TQRbTFRxARAAwqL3u/cPDA+BhU9ghtAkC+gyC5smWUL1FwTQ9CwTqcQpKt85PoaHn8sc5ctt Aj2fNT/F2vqQx/BthVOdkhj9LCwuslqBIqbri3XUyMLVV/Tf+ydzHW2AjufCowwgBguxedD1 f9Snkv+As7ZgMg/GtDqDiCWBFg9PneKvr+FPPd2WmrI8Kium4X5Zjs/a6OGUWVcIBoPpu088 z/0tlKYjTFLhoIEsf6ll4KvRQZIyGxclg3RBEuN+wgMbKppdUf2DBXYeCyrrPx809CUFzcik O99drWti2CV1gF8bnbUvfCewxwqgVKtHl2kfsm2+/lgG4CTyvnvWqUyHICZUqISdz5GidaXn TcPlsAeo2YU2NXbjwnmxzJEP/4FxgsjYIUbbxdmsK+PGre7HmGmaDZ8K77L3yHr/K7AH8mFs WUM5KiW4SnKyIQvdHkZMpvE4XrrirlZ+JI5vE043GzzpS2CGo0NFQmDJLRbpN/KQY6dkNVgA L0aDxJtAO1rXKYDSrvpL80bYyskQ4ivUa06v9SM2/bHi9bnp3Nf/fK6ErWKWmDOHWrnTgRML oQpcxoVPxw2CwyWT1069Y/CWwgnbj34+LMwMUYhPEZMitABpQE74dEtIFh0c2scm3K2QGhOP KQK3szqmXuX6MViMZLDh/B7FXLQyqwMBnZygfzZFM9vpDskAEQEAAcLBjQQYAQoAIBYhBJCO xzCORGzNhSwNSwGvsOSb28rrBQJbTFRxAhsMACEJEAGvsOSb28rrFiEEkI7HMI5EbM2FLA1L Aa+w5Jvbyuvvbg//S3d1+XL568K5BTHXaYxSqCeMqYbV9rPhEHyk+rzKtwNXSbSO8x0xZutL gYV+nkW0KMPH5Bz3I1xiRKAkiX/JLcMfx2HAXJ1Cv2rpR6bxyCGBJmuwR68uMS/gKe6AWwTY q2kt1rtZPjGl9OwVoWGJKbu2pFBLWmLAnHlXOL6WDSE1Mz2Ah3jMHOaSyAgPu1XSNa600gMJ QrSxgbe7bW72gCjeHcrIjfv+uh5cZ5/J/edpWXRuE4Tz82nxudBIHE2vnQEoJrXOh2kAJiYs G+IllDqFKDPrnS0R3DenBNG0Ir8h9W6heETnhQUc9NDFCSr81Mp0fROdBfYZnQzgSZMjN2eY pkNEWshJER4ZYY+7hAmqI51HnsKuM46QINh00jJHRMykW3TBMlwnUFxZ0gplAecjCFC7g2zj g1qNxLnxMS4wCsyEVhCkPyYnS8zuoa4ZUH37CezD01Ph4O1saln5+M4blHCEAUpZIkTGpUoi SEwtoxu6EEUYfbcjWgzJCs023hbRykZlFALoRNCwVz/FnPuVu291jn9kjvCTEeE6g2dCtOrO ukuXzk1tIeeoggsU7AJ0bzP7QOEhEckaBbP4k6ic26LJGWNMinllePyEMXzsgmMHVN//8wDT NWaanhP/JZ1v5Mfn8s1chIqC0sJIw73RvvuBkOa+jx0OwW3RFoQ= Message-ID: Date: Wed, 15 Jan 2020 16:32:07 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <6f643816-a7dc-f3bb-d521-b6ac104918d6@suse.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/01/2020 11:09, Jürgen Groß wrote: > On 15.01.20 11:54, Sergey Dyasli wrote: >> 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 >> >> 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? > > Change set_pmd_early_shadow() like the following: > > #ifdef CONFIG_XEN_PV > static inline void set_pmd_early_shadow(pmd_t *pmd, pte_t *early_shadow) > { > static bool pmd_populated = false; > > 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, pte_t *early_shadow) > { > pmd_populate_kernel(&init_mm, pmd, early_shadow); > } > #endif > > ... and move it to include/xen/xen-ops.h and call it with > lm_alias(kasan_early_shadow_pte) as the second parameter. Your suggestion to use ifdef is really good, especially now when I figured out that CONFIG_XEN_PV implies X86. But I don't like the idea of kasan code calling a non-empty function from xen-ops.h when CONFIG_XEN_PV is not defined. I'd prefer to keep set_pmd_early_shadow() in mm/kasan/init.c with the suggested ifdef. -- Thanks, Sergey