linux-kernel - RE: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write

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Message-ID: <973e772012ce4f0f9a689fe33608236a@AcuMS.aculab.com>
Date:   Tue, 11 Feb 2020 14:34:11 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Xiaoyao Li' <xiaoyao.li@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        "Borislav Petkov" <bp@...en8.de>,
        Andy Lutomirski <luto@...capital.net>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write

From: Xiaoyao Li
> Sent: 11 February 2020 14:03
...
> Alright, I don't know the history of TEST_CTRL, there is a bit 31 in it
> which means "Disable LOCK# assertion for split locked access" when set.
> Bit 31 exists for a long period, but linux seems not use it so I guess
> it may be a testing purpose bit.

My brain remembers something about some system just ignoring
locked accesses for misaligned transfers.
Trouble is it was probably nearly 30 years ago and there are
no details coming out of 'long term storage'.

It might be that some systems I had either set this bit
or acted as if it was set.

	David

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