linux-kernel - Re: [PATCH 00/15] kasan: x86: arm64: risc-v: KASAN tag-based mode for x86

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Message-ID: <cj2w476ui6g6bjtrnmhozgruhudjx7dbeifxtx4q26c4sqmobt@ill63v5yc3ke>
Date: Thu, 6 Feb 2025 11:40:24 +0100
From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
To: Andrey Konovalov <andreyknvl@...il.com>
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Subject: Re: [PATCH 00/15] kasan: x86: arm64: risc-v: KASAN tag-based mode
 for x86

Hello Andrey!

On 2025-02-06 at 00:40:59 +0100, Andrey Konovalov wrote:
>On Tue, Feb 4, 2025 at 6:34 PM Maciej Wieczor-Retman
><maciej.wieczor-retman@...el.com> wrote:
>>
>> ======= Introduction
>> The patchset aims to add a KASAN tag-based mode for the x86 architecture
>> with the help of the new CPU feature called Linear Address Masking
>> (LAM). Main improvement introduced by the series is 4x lower memory
>> usage compared to KASAN's generic mode, the only currently available
>> mode on x86.
>>
>> There are two logical parts to this series. The first one attempts to
>> add a new memory saving mechanism called "dense mode" to the generic
>> part of the tag-based KASAN code. The second one focuses on implementing
>> and enabling the tag-based mode for the x86 architecture by using LAM.
>
>Hi Maciej,
>
>Awesome work! Great to see SW_TAGS mode supported on x86!

Glad to hear that, it was a lot of fun to work on :)

>
>I started reviewing the patches, but this is somewhat complicated, as
>the dense mode changes are squashed together with the generic ones for
>x86 support. Could you please split this series into 2? Or at least
>reorder the patches so that everything needed for basic x86 support
>comes first and can be reviewed and tested separately.

I'll try reordering first and see if it looks nice. Since the dense mode would
make some parts arch specific I think it's better to have the two parts in one
series for easier reference. But if it turns out more convoluted I'll just split
it as you suggested.

>
>I will post the comments for things I noted so far, including for the
>dense mode changes, but I'll take a closer look after the split.
>
>Also feel free to drop the dependency on that risc-v series, as it
>doesn't get updated very often. But up to you.

Okay, I was mostly interested in the patch that redefines KASAN_SHADOW_END as
KASAN_SHADOW_OFFSET and then gets shadow addresses by using a signed offset. But
I suppose I can just take that patch and prepend my series with that? (after
applying your comments from that series)

>
>And please also update all affected parts of Documentation/dev-tools/kasan.rst.

Right, thanks for the reminder :)

>
>Thank you!

-- 
Kind regards
Maciej Wieczór-Retman