linux-kernel - Re: [PATCH] x86/mm/tlb: ignore f->new_tlb

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Date:   Fri, 8 Jul 2022 18:03:53 +0000
From:   Nadav Amit <namit@...are.com>
To:     Dave Hansen <dave.hansen@...el.com>
CC:     David Hildenbrand <david@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        X86 ML <x86@...nel.org>, Linux MM <linux-mm@...ck.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] x86/mm/tlb: ignore f->new_tlb_gen when zero

On Jul 8, 2022, at 10:09 AM, Nadav Amit <namit@...are.com> wrote:

> On Jul 8, 2022, at 10:01 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
>> ⚠ External Email
>> 
>> On 7/8/22 09:54, Nadav Amit wrote:
>>> Since the bug was not during MADV_DONTNEED there is no reason for the
>>> results to be any different.
>>> 
>>> Famous last words?
>> 
>> Considering that your patch broke the kernel a way that surprised us
>> all, I think caution is warranted.  Re-running a microbenchmark that
>> takes five minutes and stresses things a bit is the least you can do, I
>> think.
> 
> I will send it later today. I was just pointing that the failing code-path
> is different than the one I measured.

It will take some more time, since 5.19 does not want to boot on my machine,
and results from VMs are meaningless for this patch. I would look into this
unrelated failure, unless you want results from 5.18.

[    6.303945] ------------[ cut here ]------------
[    6.309209] kernel BUG at arch/x86/kernel/apic/apic.c:1598!
[    6.315537] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[    6.321275] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc4TLB+ #5
[    6.328760] Hardware name: Dell Inc. PowerEdge R630/0CNCJW, BIOS 2.9.1 12/04/2018
[    6.337236] RIP: 0010:setup_local_APIC+0x31e/0x330
[    6.342686] Code: 01 0f 85 05 ff ff ff 85 d2 7f 2b 48 8b 05 aa 37 4f 01 be 00 07 01 00 bf 50 03 00 00 48 8b 40 10 e8 37 99 fb 00 e9 04 ff ff ff <0f> 0b e8 5b 2d be 00 e9 ba 64 b8 0
[    6.363818] RSP: 0000:ffffffff82603e88 EFLAGS: 00010246
[    6.369752] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[    6.377820] RDX: 0000000000000000 RSI: 00000000fffffeff RDI: 0000000000000020
[    6.385888] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff82603da8
[    6.393956] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000031
[    6.402024] R13: 0000000000000000 R14: ffffffff82613118 R15: 0000000000000000
[    6.410091] FS:  0000000000000000(0000) GS:ffff889fff600000(0000) knlGS:0000000000000000
[    6.419250] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    6.425765] CR2: ffff88c07ffff000 CR3: 000000000260c001 CR4: 00000000000606f0
[    6.433826] Call Trace:
[    6.436646]  <TASK>
[    6.439077]  ? _printk+0x53/0x6a
[    6.442777]  apic_intr_mode_init+0xd2/0xf1
[    6.447448]  x86_late_time_init+0x1b/0x2b
[    6.452019]  start_kernel+0x5d8/0x694
[    6.456194]  secondary_startup_64_no_verify+0xce/0xdb
[    6.461933]  </TASK>
[    6.464463] Modules linked in:
[    6.467979] ---[ end trace 0000000000000000 ]---
[    6.473243] RIP: 0010:setup_local_APIC+0x31e/0x330
[    6.478704] Code: 01 0f 85 05 ff ff ff 85 d2 7f 2b 48 8b 05 aa 37 4f 01 be 00 07 01 00 bf 50 03 00 00 48 8b 40 10 e8 37 99 fb 00 e9 04 ff ff ff <0f> 0b e8 5b 2d be 00 e9 ba 64 b8 0
[    6.499865] RSP: 0000:ffffffff82603e88 EFLAGS: 00010246
[    6.505803] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[    6.513887] RDX: 0000000000000000 RSI: 00000000fffffeff RDI: 0000000000000020
[    6.521969] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff82603da8
[    6.530053] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000031
[    6.538136] R13: 0000000000000000 R14: ffffffff82613118 R15: 0000000000000000
[    6.546218] FS:  0000000000000000(0000) GS:ffff889fff600000(0000) knlGS:0000000000000000
[    6.555391] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    6.561919] CR2: ffff88c07ffff000 CR3: 000000000260c001 CR4: 00000000000606f0
[    6.570003] Kernel panic - not syncing: Attempted to kill the idle task!
[    6.577591] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---