From patchwork Wed Feb 23 01:58:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Ellerman X-Patchwork-Id: 1596457 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=HQBZsvA2; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=2404:9400:2:0:216:3eff:fee1:b9f1; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2404:9400:2:0:216:3eff:fee1:b9f1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4K3K2g2wbmz9sFt for ; Wed, 23 Feb 2022 12:58:50 +1100 (AEDT) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4K3K2f1dL6z3bYq for ; Wed, 23 Feb 2022 12:58:50 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=HQBZsvA2; dkim-atps=neutral X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4K3K2N2fcWz2xrc for ; Wed, 23 Feb 2022 12:58:36 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=HQBZsvA2; dkim-atps=neutral Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4K3K2K03cRz4xcl; Wed, 23 Feb 2022 12:58:32 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1645581515; bh=RehJM34ucrNIjQ/8HWqcWaTbkJ/NyNkOdbvyGowJxKA=; h=From:To:Cc:Subject:Date:From; b=HQBZsvA215oG4KwXCNXVcxSE1695nobzXmBVnqeXgWm+19hJhFj90D6TtQfGakr4K F1MbhjyS9GIKH4zULMfbYTirlHp4F2B6+cvn+rsh1l1T5qOuH7HpIgGpilvWwiUXpV HVJhGNBqrl623nmtjvIvmmPKbkxkrclUl1dMapEZQNPhlQN96NNN9xZWOrJ9JXpdqn kQidDuZuMcOy0ARh2CTDjRQU9MS5Eg5BZNPSe1I+Ix2gZwH+sXj0Ao6E7Yy+KuRlL0 hVlbUgsYFNJ/tVDl8vxykTZ360V/C2QssAWoIt3+QFwZpcsykrSn07nEUoWKpj7Opx 3I4bdEvwxNayw== From: Michael Ellerman To: Subject: [PATCH] powerpc/code-patching: Pre-map patch area Date: Wed, 23 Feb 2022 12:58:21 +1100 Message-Id: <20220223015821.473097-1-mpe@ellerman.id.au> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peterz@infradead.org, pmenzel@molgen.mpg.de Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Paul reported a warning with DEBUG_ATOMIC_SLEEP=y: BUG: sleeping function called from invalid context at include/linux/sched/mm.h:256 in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 1, name: swapper/0 preempt_count: 0, expected: 0 ... Call Trace: dump_stack_lvl+0xa0/0xec (unreliable) __might_resched+0x2f4/0x310 kmem_cache_alloc+0x220/0x4b0 __pud_alloc+0x74/0x1d0 hash__map_kernel_page+0x2cc/0x390 do_patch_instruction+0x134/0x4a0 arch_jump_label_transform+0x64/0x78 __jump_label_update+0x148/0x180 static_key_enable_cpuslocked+0xd0/0x120 static_key_enable+0x30/0x50 check_kvm_guest+0x60/0x88 pSeries_smp_probe+0x54/0xb0 smp_prepare_cpus+0x3e0/0x430 kernel_init_freeable+0x20c/0x43c kernel_init+0x30/0x1a0 ret_from_kernel_thread+0x5c/0x64 Peter pointed out that this is because do_patch_instruction() has disabled interrupts, but then map_patch_area() calls map_kernel_page() then hash__map_kernel_page() which does a sleeping memory allocation. We only see the warning in KVM guests with SMT enabled, which is not particularly common, or on other platforms if CONFIG_KPROBES is disabled, also not common. The reason we don't see it in most configurations is that another path that happens to have interrupts enabled has allocated the required page tables for us, eg. there's a path in kprobes init that does that. That's just pure luck though. As Christophe suggested, the simplest solution is to do a dummy map/unmap when we initialise the patching, so that any required page table levels are pre-allocated before the first call to do_patch_instruction(). This works because the unmap doesn't free any page tables that were allocated by the map, it just clears the PTE, leaving the page table levels there for the next map. Reported-by: Paul Menzel Debugged-by: Peter Zijlstra Suggested-by: Christophe Leroy Signed-off-by: Michael Ellerman --- arch/powerpc/lib/code-patching.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 906d43463366..00c68e7fb11e 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -43,9 +43,14 @@ int raw_patch_instruction(u32 *addr, ppc_inst_t instr) #ifdef CONFIG_STRICT_KERNEL_RWX static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); +static int map_patch_area(void *addr, unsigned long text_poke_addr); +static void unmap_patch_area(unsigned long addr); + static int text_area_cpu_up(unsigned int cpu) { struct vm_struct *area; + unsigned long addr; + int err; area = get_vm_area(PAGE_SIZE, VM_ALLOC); if (!area) { @@ -53,6 +58,15 @@ static int text_area_cpu_up(unsigned int cpu) cpu); return -1; } + + // Map/unmap the area to ensure all page tables are pre-allocated + addr = (unsigned long)area->addr; + err = map_patch_area(empty_zero_page, addr); + if (err) + return err; + + unmap_patch_area(addr); + this_cpu_write(text_poke_area, area); return 0;