From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 65F1936F426 for ; Mon, 23 Feb 2026 19:41:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771875668; cv=none; b=NF4hnDqdW+K36XqPc/WurMqtqrAPjG47tamS78esemfk7RulLdLBakcKwndsXBliiXmRectRlIDVQ8E5MkoA3DA29pOOhzqJypyLlG/IAQLVEt0NpTxyr+mRTR9SHwc2dQ5Q2rHz1mCZTrRfpzeOTabRaY8ow7/+/qRn2Yvi52A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771875668; c=relaxed/simple; bh=WEA6P95rkpZGExTdoo0RdXuU9UiczYMaZDEepqmmNf8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mv2KSHV9pzHLH7Nj57VsD24we2d5mNjWNlXPyN5q/Ds1L0fRy+bpY1S92h8kQgIi6bucMWTuxGE6KuL/55WSKHK7+qf2XfxaaIKsNjez0KEjdbuAFsqjZJES6egH+ofNkISH/x4c5VPD/b8PHMsqvlcmyiq256dh+mSqfW3mQvg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HHE7diwS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HHE7diwS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8185CC116C6; Mon, 23 Feb 2026 19:41:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771875667; bh=WEA6P95rkpZGExTdoo0RdXuU9UiczYMaZDEepqmmNf8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HHE7diwSspbMM7gFWFYKCy8L8ucllyJCnYSvp3iCleZ1TGGXI2au3miXIunOKIsJ+ VBDHHzqtvSaMet6brn85yJfH+ndBeWY2y4uqBzIxb8dno1e3MfFjQX6Gc2yjDyIxSP pBA86kZeTw5qvbxPYqJaBLHt/9WEWufkPKOEqM+K7zVMGGe1f4G/Kqvl5ts4IeFIZr qszRyR4+lO2yG6+Clh6gDC+tt/IavaWv8EGjzPasQgM8umTyGCAEVhaQiAGuuwzQPL 7QcSsNYgrrxCHge0KyVDHNl0ha1DYW70VaWBP6Kq9iNSPldoa66XNX1nIeg5G0ijvw elPrtlC69zfwg== Date: Mon, 23 Feb 2026 21:40:59 +0200 From: Mike Rapoport To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Andrew Morton , David Hildenbrand , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org Subject: Re: [PATCH v3 24/29] arch, mm: consolidate initialization of SPARSE memory model Message-ID: References: <20260111082105.290734-1-rppt@kernel.org> <20260111082105.290734-25-rppt@kernel.org> <20260223144108-dcace0b9-02e8-4b67-a7ce-f263bed36f26@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260223144108-dcace0b9-02e8-4b67-a7ce-f263bed36f26@linutronix.de> Hi Thomas, On Mon, Feb 23, 2026 at 02:52:45PM +0100, Thomas Weißschuh wrote: > Hi everyone, > > On Sun, Jan 11, 2026 at 10:20:58AM +0200, Mike Rapoport wrote: > > Every architecture calls sparse_init() during setup_arch() although the > > data structures created by sparse_init() are not used until the > > initialization of the core MM. > > > > Beside the code duplication, calling sparse_init() from architecture > > specific code causes ordering differences of vmemmap and HVO initialization > > on different architectures. > > > > Move the call to sparse_init() from architecture specific code to > > free_area_init() to ensure that vmemmap and HVO initialization order is > > always the same. > > This broke the boot on RISC-V 32-bit (rv32_defconfig) for me. > > Specifically if sparse_init() is *not* called before the following callchain, > the kernel dies at that point. > > start_kernel() > setup_arch() > apply_boot_alternatives() > _apply_alternatives() > riscv_cpufeature_patch_func() > patch_text_nosync() > riscv_alternative_fix_offsets() Hm, most architectures do alternatives patching much later in the boot, when much more subsystems (including mm) is already initialized. Any particular reason riscv does it that early? > Simple reproducer, using kunit: > > ./tools/testing/kunit/kunit.py run --raw_output=all --make_options LLVM=1 --arch riscv32 --kconfig_add CONFIG_SPARSEMEM_MANUAL=y --kconfig_add CONFIG_SPARSEMEM=y Looking at patch_map it's quite clear why movement of sparse_init() cased a crash: if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) page = phys_to_page(__pa_symbol(addr)); phys_to_page() with CONFIG_SPARSEMEM=y will try to access memory section that are initialized in sparse_init(). What I don't understand is why patch_map() needs a struct page for kernel text patching at all, __pa_symbol() should work just fine. And the BUG_ON(!page) is completely bogus for phys_to_page() conversion, because that one is pure arithmetics. If moving apply_boot_alternatives() is not an option for riscv, something like the patch below should fix the issue with access to nonexistent memory sections. But I think moving apply_boot_alternatives() later in boot would make things less fragile. diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index db13c9ddf9e3..89b3c13f2865 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -43,18 +43,19 @@ static __always_inline void *patch_map(void *addr, const unsigned int fixmap) { uintptr_t uintaddr = (uintptr_t) addr; struct page *page; + phys_addr_t phys; - if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) - page = phys_to_page(__pa_symbol(addr)); - else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) + if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) { + phys = __pa_symbol(addr); + } else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) { page = vmalloc_to_page(addr); - else + BUG_ON(!page); + phys = page_to_phys(page); + } else { return addr; + } - BUG_ON(!page); - - return (void *)set_fixmap_offset(fixmap, page_to_phys(page) + - offset_in_page(addr)); + return (void *)set_fixmap_offset(fixmap, phys + offset_in_page(addr)); } static void patch_unmap(int fixmap) -- Sincerely yours, Mike.