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Tue, 11 Mar 2025 06:01:44 -0700 (PDT) Received: from wheely.local0.net ([118.208.151.101]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ff4e773dddsm11822318a91.12.2025.03.11.06.01.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Mar 2025 06:01:43 -0700 (PDT) From: Nicholas Piggin To: qemu-devel@nongnu.org Cc: Nicholas Piggin , qemu-ppc@nongnu.org Subject: [PULL 65/72] target/ppc: Avoid warning message for zero process table entries Date: Tue, 11 Mar 2025 22:57:59 +1000 Message-ID: <20250311125815.903177-66-npiggin@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250311125815.903177-1-npiggin@gmail.com> References: <20250311125815.903177-1-npiggin@gmail.com> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::102d; envelope-from=npiggin@gmail.com; helo=mail-pj1-x102d.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org A translation that encounters a process table entry that is zero is something that Linux does to cause certain kernel NULL pointer dereferences to fault. It is not itself a programming error, so avoid the guest error log. Message-ID: <20241219034035.1826173-5-npiggin@gmail.com> Signed-off-by: Nicholas Piggin --- target/ppc/mmu-radix64.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/target/ppc/mmu-radix64.c b/target/ppc/mmu-radix64.c index 1d3d9e1be7..461eda4a3d 100644 --- a/target/ppc/mmu-radix64.c +++ b/target/ppc/mmu-radix64.c @@ -571,6 +571,20 @@ static int ppc_radix64_process_scoped_xlate(PowerPCCPU *cpu, prtbe0 = ldq_phys(cs->as, h_raddr); } + /* + * Some Linux uses a zero process table entry in PID!=0 for kernel context + * without userspace in order to fault on NULL dereference, because using + * PIDR=0 for the kernel causes the Q0 page table to be used to translate + * Q3 as well. Check for that case here to avoid the invalid configuration + * message. + */ + if (unlikely(!prtbe0)) { + if (guest_visible) { + ppc_radix64_raise_si(cpu, access_type, eaddr, DSISR_R_BADCONFIG); + } + return 1; + } + /* Walk Radix Tree from Process Table Entry to Convert EA to RA */ *g_page_size = PRTBE_R_GET_RTS(prtbe0); base_addr = prtbe0 & PRTBE_R_RPDB;