kernel/arch, branch linux-6.6.y

Revert "x86/kexec: add a sanity check on previous kernel's ima kexec buffer"

2026-03-05T14:56:36Z

This reverts commit c5489d04337b47e93c0623e8145fcba3f5739efd. The commit introduces a call to ima_validate_range() in arch/x86/kernel/setup.c, but the function declaration is not available in the 6.12 stable tree, resulting in build failures due to implicit function declaration errors across multiple stable branches. Signed-off-by: Sasha Levin

arm64: Fix sampling the "stable" virtual counter in preemptible section

2026-03-04T12:21:20Z

[ Upstream commit e5cb94ba5f96d691d8885175d4696d6ae6bc5ec9 ] Ben reports that when running with CONFIG_DEBUG_PREEMPT, using __arch_counter_get_cntvct_stable() results in well deserves warnings, as we access a per-CPU variable without preemption disabled. Fix the issue by disabling preemption on reading the counter. We can probably do a lot better by not disabling preemption on systems that do not require horrible workarounds to return a valid counter value, but this plugs the issue for the time being. Fixes: 29cc0f3aa7c6 ("arm64: Force the use of CNTVCT_EL0 in __delay()") Reported-by: Ben Horgan Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/aZw3EGs4rbQvbAzV@e134344.arm.com Tested-by: Ben Horgan Tested-by: André Draszik Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

arm64: Force the use of CNTVCT_EL0 in __delay()

2026-03-04T12:21:20Z

[ Upstream commit 29cc0f3aa7c64d3b3cb9d94c0a0984ba6717bf72 ] Quentin forwards a report from Hyesoo Yu, describing an interesting problem with the use of WFxT in __delay() when a vcpu is loaded and that KVM is *not* in VHE mode (either nVHE or hVHE). In this case, CNTVOFF_EL2 is set to a non-zero value to reflect the state of the guest virtual counter. At the same time, __delay() is using get_cycles() to read the counter value, which is indirected to reading CNTPCT_EL0. The core of the issue is that WFxT is using the *virtual* counter, while the kernel is using the physical counter, and that the offset introduces a really bad discrepancy between the two. Fix this by forcing the use of CNTVCT_EL0, making __delay() consistent irrespective of the value of CNTVOFF_EL2. Reported-by: Hyesoo Yu Reported-by: Quentin Perret Reviewed-by: Quentin Perret Fixes: 7d26b0516a0d ("arm64: Use WFxT for __delay() when possible") Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/ktosachvft2cgqd5qkukn275ugmhy6xrhxur4zqpdxlfr3qh5h@o3zrfnsq63od Cc: stable@vger.kernel.org Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

x86/kexec: Copy ACPI root pointer address from config table

2026-03-04T12:21:19Z

[ Upstream commit e00ac9e5afb5d80c0168ec88d8e8662a54af8249 ] Dave reports that kexec may fail when the first kernel boots via the EFI stub but without EFI runtime services, as in that case, the RSDP address field in struct bootparams is never assigned. Kexec copies this value into the version of struct bootparams that it provides to the incoming kernel, which may have no other means to locate the ACPI root pointer. So take the value from the EFI config tables if no root pointer has been set in the first kernel's struct bootparams. Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot") Cc: # v6.1 Reported-by: Dave Young Tested-by: Dave Young Link: https://lore.kernel.org/linux-efi/aZQg_tRQmdKNadCg@darkstar.users.ipa.redhat.com/ Signed-off-by: Ard Biesheuvel Signed-off-by: Sasha Levin

LoongArch: Disable instrumentation for setup_ptwalker()

2026-03-04T12:21:17Z

[ Upstream commit 7cb37af61f09c9cfd90c43c9275307c16320cbf2 ] According to Documentation/dev-tools/kasan.rst, software KASAN modes use compiler instrumentation to insert validity checks. Such instrumentation might be incompatible with some parts of the kernel, and therefore needs to be disabled, just use the attribute __no_sanitize_address to disable instrumentation for the low level function setup_ptwalker(). Otherwise bringing up the secondary CPUs failed when CONFIG_KASAN is set (especially when PTW is enabled), here are the call chains: smpboot_entry() start_secondary() cpu_probe() per_cpu_trap_init() tlb_init() setup_tlb_handler() setup_ptwalker() The reason is the PGD registers are configured in setup_ptwalker(), but KASAN instrumentation may cause TLB exceptions before that. Cc: stable@vger.kernel.org Signed-off-by: Tiezhu Yang Signed-off-by: Huacai Chen Signed-off-by: Sasha Levin

LoongArch: Guard percpu handler under !CONFIG_PREEMPT_RT

2026-03-04T12:21:16Z

[ Upstream commit 70b0faae3590c628a98a627a10e5d211310169d4 ] After commit 88fd2b70120d ("LoongArch: Fix sleeping in atomic context for PREEMPT_RT"), it should guard percpu handler under !CONFIG_PREEMPT_RT to avoid redundant operations. Cc: stable@vger.kernel.org Signed-off-by: Tiezhu Yang Signed-off-by: Huacai Chen Signed-off-by: Sasha Levin

LoongArch: Prefer top-down allocation after arch_mem_init()

2026-03-04T12:21:16Z

[ Upstream commit 2172d6ebac9372eb01fe4505a53e18cb061e103b ] Currently we use bottom-up allocation after sparse_init(), the reason is sparse_init() need a lot of memory, and bottom-up allocation may exhaust precious low memory (below 4GB). On the other hand, SWIOTLB and CMA need low memories for DMA32, so swiotlb_init() and dma_contiguous_reserve() need bottom-up allocation. Since swiotlb_init() and dma_contiguous_reserve() are both called in arch_mem_init(), we no longer need bottom-up allocation after that. So we set the allocation policy to top-down at the end of arch_mem_init(), in order to avoid later memory allocations (such as KASAN) exhaust low memory. This solve at least two problems: 1. Some buggy BIOSes use 0xfd000000~0xfe000000 for secondary CPUs, but didn't reserve this range, which causes smpboot failures. 2. Some DMA32 devices, such as Loongson-DRM and OHCI, cannot work with KASAN enabled. Cc: stable@vger.kernel.org Signed-off-by: Huacai Chen Signed-off-by: Sasha Levin

LoongArch: Make cpumask_of_node() robust against NUMA_NO_NODE

2026-03-04T12:21:16Z

[ Upstream commit 94b0c831eda778ae9e4f2164a8b3de485d8977bb ] The arch definition of cpumask_of_node() cannot handle NUMA_NO_NODE - which is a valid index - so add a check for this. Cc: stable@vger.kernel.org Signed-off-by: John Garry Signed-off-by: Huacai Chen Signed-off-by: Sasha Levin

MIPS: rb532: Fix MMIO UART resource registration

2026-03-04T12:21:16Z

[ Upstream commit e93bb4b76cfefb302534246e892c7667491cb8cc ] Since commit 6e690d54cfa8 ("serial: 8250: fix return error code in serial8250_request_std_resource()"), registering an 8250 MMIO port without mapbase no longer works, as the resource range is derived from mapbase/mapsize. Populate mapbase and mapsize accordingly. Also drop ugly membase KSEG1 pointer and set UPF_IOREMAP instead, letting the 8250 core perform the ioremap. Fixes: 6e690d54cfa8 ("serial: 8250: fix return error code in serial8250_request_std_resource()") Cc: stable@vger.kernel.org Reported-by: Waldemar Brodkorb Link: https://lore.kernel.org/linux-mips/aX-d0ShTplHKZT33@waldemar-brodkorb.de/ Signed-off-by: Jiaxun Yang Signed-off-by: Thomas Bogendoerfer Signed-off-by: Sasha Levin

parisc: kernel: replace kfree() with put_device() in create_tree_node()

2026-03-04T12:21:16Z

[ Upstream commit dcf69599c47f29ce0a99117eb3f9ddcd2c4e78b6 ] If device_register() fails, put_device() is the correct way to drop the device reference. Found by code review. Fixes: 1070c9655b90 ("[PA-RISC] Fix must_check warnings in drivers.c") Cc: stable@vger.kernel.org Signed-off-by: Haoxiang Li Signed-off-by: Helge Deller Signed-off-by: Sasha Levin