From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1891DC433FE for ; Mon, 21 Nov 2022 19:59:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231728AbiKUT75 (ORCPT ); Mon, 21 Nov 2022 14:59:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50766 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229840AbiKUT74 (ORCPT ); Mon, 21 Nov 2022 14:59:56 -0500 Received: from mail-lf1-x133.google.com (mail-lf1-x133.google.com [IPv6:2a00:1450:4864:20::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8D6A4385A for ; Mon, 21 Nov 2022 11:59:54 -0800 (PST) Received: by mail-lf1-x133.google.com with SMTP id a29so20383953lfj.9 for ; Mon, 21 Nov 2022 11:59:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=GSLg3lnlnQB1hP6JwVcBXUauPug+4FyuOo+oBexYadI=; b=Kk3GxXmPIvdzM6UsD2FitntVNHVBbwxpLrNVpPWxak/p00HCqWN+Lt4/xZ3Ztihhei UyO1MG2KuzYDgBBi/lBG8VjFOQW88dQbKu+QF/7mBmXvuovQk+dROY1mc2X9Oh12/JD9 XU/gqQWmZXdsFf9UbZP3Yt5TmD99KyaDJRg178vIebxQAnAxLpd5tXIyrUTcV5qODl8o ndjpcGChExJKvne+P9T0Sx5p75qw+QJyvYWEXkRRZTR4MjcgmgCAw0GogABcKJ5bo+B0 GnVozVDbWeph/Xvh5SIHFJxji2+prAXDUmPsMvHKpzx8H02rRriNAvIAiKLpnjxocyuR yWKQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=GSLg3lnlnQB1hP6JwVcBXUauPug+4FyuOo+oBexYadI=; b=lWB9SjkoJrZGFqWxY1QgmL9F9cAcFWAXe/uMpNAca5J0VWV0UGwEyh9WzKOiRRcIuH zAt/HfM2Oq32DFEyppGeTfPqLEtoacI0NL2YCghvPmcAiEzo0Ty8PFc/yhlop1rX2L2w zTY2DW1b0HK/RGcolXIM9HO/EUFn86BPmThZAV0bO2Qg8aOeNbrkfNRZ+OhNvL7MPkW4 2ZhgFFdbTYJuuUtuLnfhbVBg8B5lHjt8GoyJfIJm4aoDHur2a/7/E81HRKl1UIOviKFM Zqw46sPI+MNT5BC51S3VMwk3P4stIiSCOP/angTKZ06x8lLchpZwRNKiftiTaa5tdej4 1Pdw== X-Gm-Message-State: ANoB5pm6LcuvRyQpd5OVOpWB5/+zTeNZG2l7ms5UdF2mYWo1dwn68oE5 g5jNhuoo1HGot6j27yMrF98= X-Google-Smtp-Source: AA0mqf614JoCXiwhlXfpZPATW4kb+3f4M4d4pYgxugmAgR7pbvKpon7OmkDr+g3KCOiv15Z1E2ZrEw== X-Received: by 2002:ac2:52b6:0:b0:4a8:df88:f4d2 with SMTP id r22-20020ac252b6000000b004a8df88f4d2mr6282701lfm.463.1669060792940; Mon, 21 Nov 2022 11:59:52 -0800 (PST) Received: from curiosity ([5.188.167.245]) by smtp.gmail.com with ESMTPSA id be40-20020a056512252800b00497a61453a9sm2162437lfb.243.2022.11.21.11.59.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Nov 2022 11:59:51 -0800 (PST) Date: Mon, 21 Nov 2022 22:59:50 +0300 From: Sergey Matyukevich To: guoren@kernel.org Cc: 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, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren , Anup Patel , Palmer Dabbelt Subject: Re: [PATCH V3] riscv: asid: Fixup stale TLB entry cause application crash Message-ID: References: <20221111075902.798571-1-guoren@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221111075902.798571-1-guoren@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > 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 > --- > 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); > } Tested-by: Sergey Matyukevich Thanks, Sergey