From: Dave Hansen <dave.hansen@intel.com>
To: Joel Fernandes <joelagnelf@nvidia.com>,
Valentin Schneider <vschneid@redhat.com>
Cc: Jann Horn <jannh@google.com>,
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Subject: Re: [PATCH v4 29/30] x86/mm, mm/vmalloc: Defer flush_tlb_kernel_range() targeting NOHZ_FULL CPUs
Date: Wed, 19 Feb 2025 12:32:30 -0800 [thread overview]
Message-ID: <e03a8e82-af4c-40fb-bd91-f268206f1d93@intel.com> (raw)
In-Reply-To: <adcf012e-57ef-4b54-8b19-2273aca41ec6@nvidia.com>
On 2/19/25 09:08, Joel Fernandes wrote:
>> Pretty much so yeah. That is, *if* there such a vmalloc'd address access in
>> early entry code - testing says it's not the case, but I haven't found a
>> way to instrumentally verify this.
> Ok, thanks for confirming. Maybe there is an address sanitizer way of verifying,
> but yeah it is subtle and there could be more than one way of solving it. Too
> much 'fun' 😉
For debugging, you could just make a copy of part or all of the page
tables and run the NOHZ_FULL tasks from those while they're in
userspace. Then, instead of flushing the TLB in the deferred work, you
switch over to the "real" page tables.
That would _behave_ like a CPU with a big TLB and really old, crusty TLB
entries from the last time the kernel ran.
BTW, the other option for all of this is just to say that if you want
IPI-free TLB flushing that you need to go buy some hardware with it as
opposed to all of this complexity.
next prev parent reply other threads:[~2025-02-19 20:32 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-14 17:51 [PATCH v4 00/30] context_tracking,x86: Defer some IPIs until a user->kernel transition Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 01/30] objtool: Make validate_call() recognize indirect calls to pv_ops[] Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 02/30] objtool: Flesh out warning related to pv_ops[] calls Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 03/30] rcu: Add a small-width RCU watching counter debug option Valentin Schneider
2025-01-21 13:56 ` Frederic Weisbecker
2025-01-14 17:51 ` [PATCH v4 04/30] rcutorture: Make TREE04 use CONFIG_RCU_DYNTICKS_TORTURE Valentin Schneider
2025-01-21 14:00 ` Frederic Weisbecker
2025-01-14 17:51 ` [PATCH v4 05/30] jump_label: Add annotations for validating noinstr usage Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 06/30] static_call: Add read-only-after-init static calls Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 07/30] x86/paravirt: Mark pv_sched_clock static call as __ro_after_init Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 08/30] x86/idle: Mark x86_idle " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 09/30] x86/paravirt: Mark pv_steal_clock " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 10/30] riscv/paravirt: " Valentin Schneider
2025-01-14 18:29 ` Andrew Jones
2025-01-14 17:51 ` [PATCH v4 11/30] loongarch/paravirt: " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 12/30] arm64/paravirt: " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 13/30] arm/paravirt: " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 14/30] perf/x86/amd: Mark perf_lopwr_cb " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 15/30] sched/clock: Mark sched_clock_running key " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 16/30] x86/speculation/mds: Mark mds_idle_clear key as allowed in .noinstr Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 17/30] sched/clock, x86: Mark __sched_clock_stable " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 18/30] x86/kvm/vmx: Mark vmx_l1d_should flush and vmx_l1d_flush_cond keys " Valentin Schneider
2025-01-14 21:19 ` Sean Christopherson
2025-01-17 9:50 ` Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 19/30] stackleack: Mark stack_erasing_bypass key " Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 20/30] objtool: Add noinstr validation for static branches/calls Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 21/30] context_tracking: Explicitely use CT_STATE_KERNEL where it is missing Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 22/30] context_tracking: Exit CT_STATE_IDLE upon irq/nmi entry Valentin Schneider
2025-01-22 0:22 ` Frederic Weisbecker
2025-01-22 1:04 ` Sean Christopherson
2025-01-27 11:17 ` Valentin Schneider
2025-02-07 17:06 ` Valentin Schneider
2025-02-07 18:37 ` Frederic Weisbecker
2025-02-10 17:36 ` Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 23/30] context_tracking: Turn CT_STATE_* into bits Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 24/30] context-tracking: Introduce work deferral infrastructure Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 25/30] context_tracking,x86: Defer kernel text patching IPIs Valentin Schneider
2025-01-14 21:13 ` Sean Christopherson
2025-01-14 21:48 ` Sean Christopherson
2025-01-17 9:54 ` Valentin Schneider
2025-01-17 9:47 ` Valentin Schneider
2025-01-17 17:15 ` Sean Christopherson
2025-01-20 13:53 ` Valentin Schneider
2025-01-14 21:26 ` Sean Christopherson
2025-01-24 10:48 ` K Prateek Nayak
2025-01-14 17:51 ` [PATCH v4 26/30] x86,tlb: Make __flush_tlb_global() noinstr-compliant Valentin Schneider
2025-01-14 21:45 ` Dave Hansen
2025-01-17 13:44 ` Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 27/30] x86/tlb: Make __flush_tlb_local() noinstr-compliant Valentin Schneider
2025-01-14 21:24 ` Sean Christopherson
2025-01-14 17:51 ` [PATCH v4 28/30] x86/tlb: Make __flush_tlb_all() noinstr Valentin Schneider
2025-01-14 17:51 ` [PATCH v4 29/30] x86/mm, mm/vmalloc: Defer flush_tlb_kernel_range() targeting NOHZ_FULL CPUs Valentin Schneider
2025-01-14 18:16 ` Jann Horn
2025-01-17 15:25 ` Valentin Schneider
2025-01-17 15:52 ` Jann Horn
2025-01-17 16:53 ` Valentin Schneider
2025-02-19 15:05 ` Joel Fernandes
2025-02-19 16:18 ` Valentin Schneider
2025-02-19 17:08 ` Joel Fernandes
2025-02-19 20:32 ` Dave Hansen [this message]
2025-01-27 15:51 ` Will Deacon
2025-02-10 18:36 ` Valentin Schneider
2025-02-10 22:08 ` Jann Horn
2025-02-11 13:33 ` Valentin Schneider
2025-02-11 14:03 ` Mark Rutland
2025-02-11 16:09 ` Valentin Schneider
2025-02-11 14:22 ` Dave Hansen
2025-02-11 16:10 ` Valentin Schneider
2025-02-18 22:40 ` Valentin Schneider
2025-02-19 0:39 ` Dave Hansen
2025-02-19 15:13 ` Valentin Schneider
2025-02-19 20:25 ` Dave Hansen
2025-02-20 17:10 ` Valentin Schneider
2025-02-20 17:38 ` Dave Hansen
2025-02-26 16:52 ` Valentin Schneider
2025-03-25 17:52 ` Valentin Schneider
2025-03-25 18:41 ` Jann Horn
2025-03-26 8:56 ` Valentin Schneider
2025-01-17 16:11 ` Uladzislau Rezki
2025-01-17 17:00 ` Valentin Schneider
2025-01-20 11:15 ` Uladzislau Rezki
2025-01-20 16:09 ` Valentin Schneider
2025-01-21 17:00 ` Uladzislau Rezki
2025-01-24 15:22 ` Valentin Schneider
2025-01-27 10:36 ` Uladzislau Rezki
2025-01-14 17:51 ` [PATCH v4 30/30] context-tracking: Add a Kconfig to enable IPI deferral for NO_HZ_IDLE Valentin Schneider
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