linux-kernel - Re: [PATCHv16 05/17] mm: Introduce untagged_addr

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Date:   Tue, 14 Mar 2023 23:35:33 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "Torvalds, Linus" <torvalds@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kcc@...gle.com" <kcc@...gle.com>,
        "andreyknvl@...il.com" <andreyknvl@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "tarasmadan@...gle.com" <tarasmadan@...gle.com>,
        "bharata@....com" <bharata@....com>,
        "ryabinin.a.a@...il.com" <ryabinin.a.a@...il.com>,
        "glider@...gle.com" <glider@...gle.com>
Subject: Re: [PATCHv16 05/17] mm: Introduce untagged_addr_remote()

On Sun, 2023-03-12 at 14:26 +0300, Kirill A. Shutemov wrote:
> untagged_addr() removes tags/metadata from the address and brings it
> to
> the canonical form. The helper is implemented on arm64 and sparc.
> Both of
> them do untagging based on global rules.
> 
> However, Linear Address Masking (LAM) on x86 introduces per-process
> settings for untagging. As a result, untagged_addr() is now only
> suitable for untagging addresses for the current proccess.
> 
> The new helper untagged_addr_remote() has to be used when the address
> targets remote process. It requires the mmap lock for target mm to be
> taken.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Tested-by: Alexander Potapenko <glider@...gle.com>

Seems to cover all the untagged_addr() cases that were operating on a
non-current MM.

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>