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Groups > linux.kernel > #1671521
| From | Thomas Gleixner <tglx@linutronix.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking |
| Date | 2017-06-21 11:10 +0200 |
| Message-ID | <tUJOa-4bl-13@gated-at.bofh.it> (permalink) |
| References | <tUGnf-1Tn-3@gated-at.bofh.it> <tUGng-1Tn-35@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, 20 Jun 2017, Andy Lutomirski wrote:
> -/*
> - * The flush IPI assumes that a thread switch happens in this order:
> - * [cpu0: the cpu that switches]
> - * 1) switch_mm() either 1a) or 1b)
> - * 1a) thread switch to a different mm
> - * 1a1) set cpu_tlbstate to TLBSTATE_OK
> - * Now the tlb flush NMI handler flush_tlb_func won't call leave_mm
> - * if cpu0 was in lazy tlb mode.
> - * 1a2) update cpu active_mm
> - * Now cpu0 accepts tlb flushes for the new mm.
> - * 1a3) cpu_set(cpu, new_mm->cpu_vm_mask);
> - * Now the other cpus will send tlb flush ipis.
> - * 1a4) change cr3.
> - * 1a5) cpu_clear(cpu, old_mm->cpu_vm_mask);
> - * Stop ipi delivery for the old mm. This is not synchronized with
> - * the other cpus, but flush_tlb_func ignore flush ipis for the wrong
> - * mm, and in the worst case we perform a superfluous tlb flush.
> - * 1b) thread switch without mm change
> - * cpu active_mm is correct, cpu0 already handles flush ipis.
> - * 1b1) set cpu_tlbstate to TLBSTATE_OK
> - * 1b2) test_and_set the cpu bit in cpu_vm_mask.
> - * Atomically set the bit [other cpus will start sending flush ipis],
> - * and test the bit.
> - * 1b3) if the bit was 0: leave_mm was called, flush the tlb.
> - * 2) switch %%esp, ie current
> - *
> - * The interrupt must handle 2 special cases:
> - * - cr3 is changed before %%esp, ie. it cannot use current->{active_,}mm.
> - * - the cpu performs speculative tlb reads, i.e. even if the cpu only
> - * runs in kernel space, the cpu could load tlb entries for user space
> - * pages.
> - *
> - * The good news is that cpu_tlbstate is local to each cpu, no
> - * write/read ordering problems.
While the new code is really well commented, it would be a good thing to
have a single place where all of this including the ordering constraints
are documented.
> @@ -215,12 +200,13 @@ static void flush_tlb_func_common(const struct flush_tlb_info *f,
> VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[0].ctx_id) !=
> loaded_mm->context.ctx_id);
>
> - if (this_cpu_read(cpu_tlbstate.state) != TLBSTATE_OK) {
> + if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(loaded_mm))) {
> /*
> - * leave_mm() is adequate to handle any type of flush, and
> - * we would prefer not to receive further IPIs.
> + * We're in lazy mode -- don't flush. We can get here on
> + * remote flushes due to races and on local flushes if a
> + * kernel thread coincidentally flushes the mm it's lazily
> + * still using.
Ok. That's more informative.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
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[PATCH v3 00/11] PCID and improved laziness Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
[PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 15:40 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 15:50 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski <luto@kernel.org> - 2017-06-22 05:00 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Thomas Gleixner <tglx@linutronix.de> - 2017-06-22 14:30 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski <luto@kernel.org> - 2017-06-22 20:20 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Thomas Gleixner <tglx@linutronix.de> - 2017-06-22 23:30 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski <luto@kernel.org> - 2017-06-23 05:10 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Thomas Gleixner <tglx@linutronix.de> - 2017-06-23 09:30 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Nadav Amit <nadav.amit@gmail.com> - 2017-06-22 18:20 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski <luto@kernel.org> - 2017-06-22 20:20 +0200
Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Borislav Petkov <bp@alien8.de> - 2017-06-26 18:10 +0200
[PATCH v3 08/11] x86/mm: Disable PCID on 32-bit kernels Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 08/11] x86/mm: Disable PCID on 32-bit kernels Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 11:30 +0200
Re: [PATCH v3 08/11] x86/mm: Disable PCID on 32-bit kernels Borislav Petkov <bp@alien8.de> - 2017-06-23 11:30 +0200
[PATCH v3 02/11] x86/ldt: Simplify LDT switching logic Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 02/11] x86/ldt: Simplify LDT switching logic Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 10:10 +0200
Re: [PATCH v3 02/11] x86/ldt: Simplify LDT switching logic Borislav Petkov <bp@alien8.de> - 2017-06-21 11:50 +0200
[tip:x86/mm] x86/ldt: Simplify the LDT switching logic tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2017-06-22 13:20 +0200
[PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 10:10 +0200
Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Borislav Petkov <bp@alien8.de> - 2017-06-21 10:50 +0200
Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Andy Lutomirski <luto@kernel.org> - 2017-06-21 17:20 +0200
Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Nadav Amit <nadav.amit@gmail.com> - 2017-06-22 01:30 +0200
Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Andy Lutomirski <luto@kernel.org> - 2017-06-22 04:30 +0200
Re: [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Ingo Molnar <mingo@kernel.org> - 2017-06-22 09:40 +0200
[PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 11:10 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Andy Lutomirski <luto@kernel.org> - 2017-06-21 18:30 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Borislav Petkov <bp@alien8.de> - 2017-06-21 19:30 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Borislav Petkov <bp@alien8.de> - 2017-06-22 17:00 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Andy Lutomirski <luto@kernel.org> - 2017-06-22 19:50 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Borislav Petkov <bp@alien8.de> - 2017-06-22 21:10 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-06-23 15:40 +0200
Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Andy Lutomirski <luto@kernel.org> - 2017-06-23 17:30 +0200
[PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 10:10 +0200
Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Borislav Petkov <bp@alien8.de> - 2017-06-21 12:40 +0200
Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Andy Lutomirski <luto@kernel.org> - 2017-06-21 18:40 +0200
Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Borislav Petkov <bp@alien8.de> - 2017-06-21 19:10 +0200
Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Borislav Petkov <bp@alien8.de> - 2017-06-21 19:50 +0200
Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Andy Lutomirski <luto@kernel.org> - 2017-06-22 04:40 +0200
[PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 11:40 +0200
Re: [PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 15:50 +0200
Re: [PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Andy Lutomirski <luto@kernel.org> - 2017-06-21 22:40 +0200
Re: [PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Borislav Petkov <bp@alien8.de> - 2017-06-23 14:00 +0200
Re: [PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Andy Lutomirski <luto@kernel.org> - 2017-06-23 17:30 +0200
Re: [PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-06-23 15:40 +0200
[PATCH v3 07/11] x86/mm: Stop calling leave_mm() in idle code Andy Lutomirski <luto@kernel.org> - 2017-06-21 07:30 +0200
Re: [PATCH v3 07/11] x86/mm: Stop calling leave_mm() in idle code Thomas Gleixner <tglx@linutronix.de> - 2017-06-21 11:30 +0200
Re: [PATCH v3 07/11] x86/mm: Stop calling leave_mm() in idle code Andy Lutomirski <luto@kernel.org> - 2017-06-21 18:30 +0200
Re: [PATCH v3 07/11] x86/mm: Stop calling leave_mm() in idle code Borislav Petkov <bp@alien8.de> - 2017-06-23 11:10 +0200
Re: [PATCH v3 00/11] PCID and improved laziness Linus Torvalds <torvalds@linux-foundation.org> - 2017-06-21 20:30 +0200
Re: [PATCH v3 00/11] PCID and improved laziness Andy Lutomirski <luto@kernel.org> - 2017-06-22 07:30 +0200
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