linux-kernel - Re: [PATCH v2 2/2] x86/tsx: Disable TSX development mode at boot

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Date:   Tue, 29 Mar 2022 22:27:30 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
        antonio.gomez.iglesias@...ux.intel.com, neelima.krishnan@...el.com,
        stable@...r.kernel.org, Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v2 2/2] x86/tsx: Disable TSX development mode at boot

On Tue, Mar 29, 2022 at 06:24:03PM +0200, Borislav Petkov wrote:
>On Thu, Mar 10, 2022 at 02:02:09PM -0800, Pawan Gupta wrote:
>> A microcode update on some Intel processors causes all TSX transactions
>> to always abort by default [*]. Microcode also added functionality to
>> re-enable TSX for development purpose. With this microcode loaded, if
>> tsx=on was passed on the cmdline, and TSX development mode was already
>> enabled before the kernel boot, it may make the system vulnerable to TSX
>> Asynchronous Abort (TAA).
>>
>> To be on safer side, unconditionally disable TSX development mode at
>> boot. If needed, a user can enable it using msr-tools.
>>
>> [*] Intel Transactional Synchronization Extension (Intel TSX) Disable Update for Selected Processors
>>     https://cdrdv2.intel.com/v1/dl/getContent/643557
>>
>> Suggested-by: Andrew Cooper <andrew.cooper3@...rix.com>
>> Suggested-by: Borislav Petkov <bp@...en8.de>
>> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
>> Cc: <stable@...r.kernel.org>
>> ---
>>  arch/x86/include/asm/msr-index.h       |  4 +--
>>  arch/x86/kernel/cpu/cpu.h              |  1 +
>>  arch/x86/kernel/cpu/intel.c            |  4 +++
>>  arch/x86/kernel/cpu/tsx.c              | 34 ++++++++++++++++++++++++++
>>  tools/arch/x86/include/asm/msr-index.h |  4 +--
>>  5 files changed, 43 insertions(+), 4 deletions(-)
>
>Does this a lot more encapsulated version work too?

Neelima is testing this patch, she will share the results tomorrow.

Thanks,
Pawan