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Tue, 25 Aug 2026 14:58:39 +0000 X-Mizu-Trace-ID: e23b80d205abac2c X-Migadu-Flow: FLOW_OUT From: George Guo To: chenhuacai@kernel.org Cc: rppt@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, shuah@kernel.org, ardb@kernel.org, guodongtai@kylinos.cn, kernel@xen0n.name, graf@amazon.com, liukexin@kylinos.cn, loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-efi@vger.kernel.org Subject: Re: [PATCH v4 4/4] selftests/kho: add LoongArch vmtest support Date: Tue, 25 Aug 2026 22:58:33 +0800 Message-ID: <20260825145834.14244-1-dongtai.guo@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: pgfeeoi9gsp6uyeacaugwmebgr1h6917 X-Rspamd-Queue-Id: 219E340008 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1787669920-817016 X-HE-Meta: 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 o1aVmV9/ xqLar/bNYiyu1fYmGoVS8AX8t11lPa4GJ/cvf6NkmZh9W/e3BGkF0F9I7xX3mU5xaHFnQQebOCUJa8vBtluo1S9hjcJyuQ8xAYm0Tst8LxOni4AuVWj9WRPMdHXVGENh1rZwZANfK5d8G56ii7HYOFJ2k46JUb96nbimxwR5+vW16XyIbgjgKUsaI9KTLUhMkGIMc3kikEp8LG4j6WjPdAbUU9xURMEqEzArVRlb7a8fQt+iC5t18vIGNCSSdVM1WOSurNLz4LvQ/d6UN/OTbLZ++vA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Huacai, > You nearly answered nothing. > > Does your employer use different kernels for host and guest in KylinOS? No. Host and guests run the same distro kernel in KylinOS, and guests boot with edk2 firmware, so ACPI is delivered and i8042 bails out through the PNP path. That is the normal case and it never panics. I have since finished the investigation, also for the firmware-less case. The same QEMU command with two kernels gives two different results, and the difference is the kernel configuration: - A distro kernel (CONFIG_PCI_HOST_GENERIC=y) maps the PCI_IOBASE I/O window through DT PCIe host enumeration, so even without firmware the i8042 probe reads garbage and fails cleanly ("No controller found"). - The selftest's minimal kernel maps nothing there, so the same read takes a page fault in i8042_flush() and panics before userspace. So the panic needs three conditions together: a firmware-less boot, SERIO_I8042=y (the Kconfig default), and no registered PIO range -- which is only the selftest-style kernel. I agree the mainline fix is not necessary. For the selftest I will enable CONFIG_PCI_HOST_GENERIC=y in loongarch.conf instead of disabling i8042, so the selftest kernel stays closer to a normal one; the standalone patch will not be sent. Thanks, George