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X-Received-From: 2607:f8b0:400e:c01::241 Subject: [Qemu-devel] [PATCH v1 10/22] RISC-V: Hold rcu_read_lock when accessing memory X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Stefan O'Rear , Sagar Karandikar , Bastian Koppelmann , Palmer Dabbelt , Michael Clark , RISC-V Patches directly Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDKM_2 RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From reading other code that accesses memory regions directly, it appears that the rcu_read_lock needs to be held. Note: the original code for accessing RAM directly was added because there is no other way to use atomic_cmpxchg easily. Signed-off-by: Michael Clark Signed-off-by: Stefan O'Rear Signed-off-by: Palmer Dabbelt --- target/riscv/helper.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/target/riscv/helper.c b/target/riscv/helper.c index 02cbcea..228933c 100644 --- a/target/riscv/helper.c +++ b/target/riscv/helper.c @@ -209,6 +209,7 @@ restart: as the PTE is no longer valid */ MemoryRegion *mr; hwaddr l =3D sizeof(target_ulong), addr1; + rcu_read_lock(); mr =3D address_space_translate(cs->as, pte_addr, &addr1, &l, false); if (memory_access_is_direct(mr, true)) { @@ -222,16 +223,19 @@ restart: target_ulong old_pte =3D atomic_cmpxchg(pte_pa, pte, updated_pte); if (old_pte !=3D pte) { + rcu_read_unlock(); goto restart; } else { pte =3D updated_pte; } #endif } else { + rcu_read_unlock(); /* misconfigured PTE in ROM (AD bits are not preset) or * PTE is in IO space and can't be updated atomically = */ return TRANSLATE_FAIL; } + rcu_read_unlock(); } =20 /* for superpage mappings, make a fake leaf PTE for the TLB's --=20 2.7.0