Re: [PATCH 4/4] arm64: support batched/deferred tlb shootdown during page reclamation

From: Peter Zijlstra <peterz@infradead.org>
To: Barry Song <21cnbao@gmail.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org, x86@kernel.org,
	catalin.marinas@arm.com, will@kernel.org,
	linux-doc@vger.kernel.org, corbet@lwn.net, arnd@arndb.de,
	linux-kernel@vger.kernel.org, darren@os.amperecomputing.com,
	yangyicong@hisilicon.com, huzhanyuan@oppo.com,
	lipeifeng@oppo.com, zhangshiming@oppo.com, guojian@oppo.com,
	realmz6@gmail.com, Barry Song <v-songbaohua@oppo.com>,
	Nadav Amit <namit@vmware.com>, Mel Gorman <mgorman@suse.de>
Subject: Re: [PATCH 4/4] arm64: support batched/deferred tlb shootdown during page reclamation
Date: Thu, 7 Jul 2022 15:49:34 +0200	[thread overview]
Message-ID: <Ysbkbt7cvUWSShtc@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20220707125242.425242-5-21cnbao@gmail.com>

On Fri, Jul 08, 2022 at 12:52:42AM +1200, Barry Song wrote:

> diff --git a/arch/arm64/include/asm/tlbbatch.h b/arch/arm64/include/asm/tlbbatch.h
> new file mode 100644
> index 000000000000..fedb0b87b8db
> --- /dev/null
> +++ b/arch/arm64/include/asm/tlbbatch.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ARCH_ARM64_TLBBATCH_H
> +#define _ARCH_ARM64_TLBBATCH_H
> +
> +struct arch_tlbflush_unmap_batch {
> +	/*
> +	 * For arm64, HW can do tlb shootdown, so we don't
> +	 * need to record cpumask for sending IPI
> +	 */
> +};
> +
> +#endif /* _ARCH_ARM64_TLBBATCH_H */
> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> index 412a3b9a3c25..b3ed163267ca 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -272,6 +272,19 @@ static inline void flush_tlb_page(struct vm_area_struct *vma,
>  	dsb(ish);
>  }
>  
> +static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
> +					struct mm_struct *mm,
> +					struct vm_area_struct *vma,
> +					unsigned long uaddr)
> +{
> +	flush_tlb_page_nosync(vma, uaddr);
> +}

You're passing that vma along just to get the mm, that's quite silly and
trivially fixed.

diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index 412a3b9a3c25..87505ecce1f0 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -254,17 +254,23 @@ static inline void flush_tlb_mm(struct mm_struct *mm)
 	dsb(ish);
 }
 
-static inline void flush_tlb_page_nosync(struct vm_area_struct *vma,
-					 unsigned long uaddr)
+static inline void __flush_tlb_page_nosync(struct mm_struct *mm,
+					   unsigned long uaddr)
 {
 	unsigned long addr;
 
 	dsb(ishst);
-	addr = __TLBI_VADDR(uaddr, ASID(vma->vm_mm));
+	addr = __TLBI_VADDR(uaddr, ASID(mm));
 	__tlbi(vale1is, addr);
 	__tlbi_user(vale1is, addr);
 }
 
+static inline void flush_tlb_page_nosync(struct vm_area_struct *vma,
+					 unsigned long uaddr)
+{
+	return __flush_tlb_page_nosync(vma->vm_mm, uaddr);
+}
+
 static inline void flush_tlb_page(struct vm_area_struct *vma,
 				  unsigned long uaddr)
 {
