linux-kernel - Re: [PATCH v3 2/3] arm64: mm: HVO: support BBM of vmemmap pgtable safely

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Date: Mon, 15 Jan 2024 10:38:07 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Nanyong Sun <sunnanyong@...wei.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
 Will Deacon <will@...nel.org>,
 Mike Kravetz <mike.kravetz@...cle.com>,
 akpm@...ux-foundation.org,
 anshuman.khandual@....com,
 willy@...radead.org,
 wangkefeng.wang@...wei.com,
 linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH v3 2/3] arm64: mm: HVO: support BBM of vmemmap pgtable
 safely



> On Jan 13, 2024, at 17:44, Nanyong Sun <sunnanyong@...wei.com> wrote:
> 
> Implement vmemmap_update_pmd and vmemmap_update_pte on arm64 to do
> BBM(break-before-make) logic when change the page table of vmemmap
> address, they will under the init_mm.page_table_lock.
> If a translation fault of vmemmap address concurrently happened after
> pte/pmd cleared, vmemmap page fault handler will acquire the
> init_mm.page_table_lock to wait for vmemmap update to complete,
> by then the virtual address is valid again, so PF can return and
> access can continue.
> In other case, do the traditional kernel fault.
> 
> Implement vmemmap_flush_tlb_all/range on arm64 with nothing
> to do because tlb already flushed in every single BBM.
> 
> Signed-off-by: Nanyong Sun <sunnanyong@...wei.com>

Reviewed-by: Muchun Song <songmuchun@...edance.com>

Thanks.