From patchwork Fri Nov 11 07:59:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Guo Ren X-Patchwork-Id: 13039826 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 986B6C433FE for ; Fri, 11 Nov 2022 07:59:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=OGAQAl8IPV1yBclmHzpGwH1Z8wDB6aPVvtwO6rVynMs=; b=g6dQ060uVBFRsV VNCouCqwyUVOx8jDsDjhqMe65Z9CdVRh4TnU8DBgNQ+lB395r7mFGZiE5LInalosXRIEt55BoQ1W+ NTe/YHCQqIiOK5f37o88M9n7dfq2h5T/EI25OvCS7abqpz/AlLVCffW+IcgUxhk4o7T1/JNyMlbmw ryUTCaKECFV0toBcbptPpJBhg05vqPA0T8OQB2iXwQxXqfO1Wyqa5oHVISN3D/Evi+ZmpLaWfFcts ieCO4MoikLE5aurS5uYTQqhKYbw7NJOqP+dB3qHAI0OkkPqhn7ObURpLYGh1JQBqjaa9OxzUnReJT JGKJoIWVdyhQiLhPEc6Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1otOwy-00E90Y-Cf; Fri, 11 Nov 2022 07:59:44 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1otOwc-00E8yi-PD for linux-riscv@lists.infradead.org; Fri, 11 Nov 2022 07:59:24 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9A36561EC5; Fri, 11 Nov 2022 07:59:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62CDAC433D6; Fri, 11 Nov 2022 07:59:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668153560; bh=7YM4Ka0ebCuIEuz50vxHPcJkntgQCHzI1KnrlWMijZQ=; h=From:To:Cc:Subject:Date:From; b=bjKMK8gRmG1/YFfOrdCMYD4UqRsJ0z9YnF9AnNT90pFjQrCMqnd1FgjRxql1JeKX1 f1r1SlN0S0fPWiJnDgrXXPboYMK2OLqIaAO0+d9cl9Wk05qISLZjLf4IlHFP/fRNsU 4NvqEDnRiV8tTlAjqGJ/XfhXPKAH5U2Rdw6wDUmRbajXIX2DqIpE7k48zKLZrzWxYa ZNgU1Qw5/Sug37W0rZbq2wOTMLvOkbY5vi98CV+cbiSCs6+seywwaDeHoc64ZjvGOF /UW9GRmBJZbLY/0jUkj7lnrliWZCe/460qYO1tP2fMZ0rTMucpgED3PK5idBIjtyv4 JGhcG/GPH4HCg== From: guoren@kernel.org To: anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, conor.dooley@microchip.com, heiko@sntech.de, philipp.tomsich@vrull.eu, alex@ghiti.fr, hch@lst.de, ajones@ventanamicro.com, gary@garyguo.net, jszhang@kernel.org Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren , Guo Ren , Anup Patel , Palmer Dabbelt Subject: [PATCH V3] riscv: asid: Fixup stale TLB entry cause application crash Date: Fri, 11 Nov 2022 02:59:02 -0500 Message-Id: <20221111075902.798571-1-guoren@kernel.org> X-Mailer: git-send-email 2.36.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221110_235922_940978_DE2874B3 X-CRM114-Status: GOOD ( 20.91 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Guo Ren After use_asid_allocator is enabled, the userspace application will crash by stale TLB entries. Because only using cpumask_clear_cpu without local_flush_tlb_all couldn't guarantee CPU's TLB entries were fresh. Then set_mm_asid would cause the user space application to get a stale value by stale TLB entry, but set_mm_noasid is okay. Here is the symptom of the bug: unhandled signal 11 code 0x1 (coredump) 0x0000003fd6d22524 <+4>: auipc s0,0x70 0x0000003fd6d22528 <+8>: ld s0,-148(s0) # 0x3fd6d92490 => 0x0000003fd6d2252c <+12>: ld a5,0(s0) (gdb) i r s0 s0 0x8082ed1cc3198b21 0x8082ed1cc3198b21 (gdb) x /2x 0x3fd6d92490 0x3fd6d92490: 0xd80ac8a8 0x0000003f The core dump file shows that register s0 is wrong, but the value in memory is correct. Because 'ld s0, -148(s0)' used a stale mapping entry in TLB and got a wrong result from an incorrect physical address. When the task ran on CPU0, which loaded/speculative-loaded the value of address(0x3fd6d92490), then the first version of the mapping entry was PTWed into CPU0's TLB. When the task switched from CPU0 to CPU1 (No local_tlb_flush_all here by asid), it happened to write a value on the address (0x3fd6d92490). It caused do_page_fault -> wp_page_copy -> ptep_clear_flush -> ptep_get_and_clear & flush_tlb_page. The flush_tlb_page used mm_cpumask(mm) to determine which CPUs need TLB flush, but CPU0 had cleared the CPU0's mm_cpumask in the previous switch_mm. So we only flushed the CPU1 TLB and set the second version mapping of the PTE. When the task switched from CPU1 to CPU0 again, CPU0 still used a stale TLB mapping entry which contained a wrong target physical address. It raised a bug when the task happened to read that value. CPU0 CPU1 - switch 'task' in - read addr (Fill stale mapping entry into TLB) - switch 'task' out (no tlb_flush) - switch 'task' in (no tlb_flush) - write addr cause pagefault do_page_fault() (change to new addr mapping) wp_page_copy() ptep_clear_flush() ptep_get_and_clear() & flush_tlb_page() write new value into addr - switch 'task' out (no tlb_flush) - switch 'task' in (no tlb_flush) - read addr again (Use stale mapping entry in TLB) get wrong value from old phyical addr, BUG! The solution is to keep all CPUs' footmarks of cpumask(mm) in switch_mm, which could guarantee to invalidate all stale TLB entries during TLB flush. Fixes: 65d4b9c53017 ("RISC-V: Implement ASID allocator") Signed-off-by: Guo Ren Signed-off-by: Guo Ren Cc: Anup Patel Cc: Palmer Dabbelt Reviewed-by: Andrew Jones Tested-by: Sergey Matyukevich Tested-by: Lad Prabhakar Tested-by: Zong Li --- Changes in v3: - Move set/clear cpumask(mm) into set_mm (Make code more pretty with Andrew's advice) - Optimize comment description Changes in v2: - Fixup nommu compile problem (Thx Conor, Also Reported-by: kernel test robot ) - Keep cpumask_clear_cpu for noasid --- arch/riscv/mm/context.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c index 7acbfbd14557..0f784e3d307b 100644 --- a/arch/riscv/mm/context.c +++ b/arch/riscv/mm/context.c @@ -205,12 +205,24 @@ static void set_mm_noasid(struct mm_struct *mm) local_flush_tlb_all(); } -static inline void set_mm(struct mm_struct *mm, unsigned int cpu) +static inline void set_mm(struct mm_struct *prev, + struct mm_struct *next, unsigned int cpu) { - if (static_branch_unlikely(&use_asid_allocator)) - set_mm_asid(mm, cpu); - else - set_mm_noasid(mm); + /* + * The mm_cpumask indicates which harts' TLBs contain the virtual + * address mapping of the mm. Compared to noasid, using asid + * can't guarantee that stale TLB entries are invalidated because + * the asid mechanism wouldn't flush TLB for every switch_mm for + * performance. So when using asid, keep all CPUs footmarks in + * cpumask() until mm reset. + */ + cpumask_set_cpu(cpu, mm_cpumask(next)); + if (static_branch_unlikely(&use_asid_allocator)) { + set_mm_asid(next, cpu); + } else { + cpumask_clear_cpu(cpu, mm_cpumask(prev)); + set_mm_noasid(next); + } } static int __init asids_init(void) @@ -264,7 +276,8 @@ static int __init asids_init(void) } early_initcall(asids_init); #else -static inline void set_mm(struct mm_struct *mm, unsigned int cpu) +static inline void set_mm(struct mm_struct *prev, + struct mm_struct *next, unsigned int cpu) { /* Nothing to do here when there is no MMU */ } @@ -317,10 +330,7 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next, */ cpu = smp_processor_id(); - cpumask_clear_cpu(cpu, mm_cpumask(prev)); - cpumask_set_cpu(cpu, mm_cpumask(next)); - - set_mm(next, cpu); + set_mm(prev, next, cpu); flush_icache_deferred(next, cpu); }