From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40325) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ewvFH-0007Th-5M for qemu-devel@nongnu.org; Fri, 16 Mar 2018 15:42:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ewvFD-0003l5-2Z for qemu-devel@nongnu.org; Fri, 16 Mar 2018 15:42:31 -0400 Received: from mail-pf0-x242.google.com ([2607:f8b0:400e:c00::242]:37687) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ewvFC-0003ki-SW for qemu-devel@nongnu.org; Fri, 16 Mar 2018 15:42:26 -0400 Received: by mail-pf0-x242.google.com with SMTP id h11so4548144pfn.4 for ; Fri, 16 Mar 2018 12:42:26 -0700 (PDT) From: Michael Clark Date: Fri, 16 Mar 2018 12:41:07 -0700 Message-Id: <1521229281-73637-11-git-send-email-mjc@sifive.com> In-Reply-To: <1521229281-73637-1-git-send-email-mjc@sifive.com> References: <1521229281-73637-1-git-send-email-mjc@sifive.com> Subject: [Qemu-devel] [PATCH v3 10/24] RISC-V: Hold rcu_read_lock when accessing memory List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: patches@groups.riscv.org, Michael Clark , Sagar Karandikar , Bastian Koppelmann , Palmer Dabbelt >>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 on guest physical address space. Cc: Sagar Karandikar Cc: Bastian Koppelmann Signed-off-by: Michael Clark Signed-off-by: Palmer Dabbelt --- target/riscv/helper.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/target/riscv/helper.c b/target/riscv/helper.c index 02cbcea..e71633a 100644 --- a/target/riscv/helper.c +++ b/target/riscv/helper.c @@ -209,6 +209,9 @@ restart: as the PTE is no longer valid */ MemoryRegion *mr; hwaddr l = sizeof(target_ulong), addr1; + enum { success, translate_fail, restart_walk} action = success; + + rcu_read_lock(); mr = address_space_translate(cs->as, pte_addr, &addr1, &l, false); if (memory_access_is_direct(mr, true)) { @@ -222,7 +225,7 @@ restart: target_ulong old_pte = atomic_cmpxchg(pte_pa, pte, updated_pte); if (old_pte != pte) { - goto restart; + action = restart_walk; } else { pte = updated_pte; } @@ -230,7 +233,14 @@ restart: } else { /* misconfigured PTE in ROM (AD bits are not preset) or * PTE is in IO space and can't be updated atomically */ - return TRANSLATE_FAIL; + action = translate_fail; + } + rcu_read_unlock(); + + switch (action) { + case success: break; + case translate_fail: return TRANSLATE_FAIL; + case restart_walk: goto restart; } } -- 2.7.0