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Date:   Wed, 19 Sep 2018 18:57:20 +0200
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Rik van Riel <riel@surriel.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: Re: [RFC PATCH 04/10 v2 ] x86/fpu: eager switch PKRU state
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On 2018-09-19 07:55:51 [+0200], Paolo Bonzini wrote:
> A kthread can do use_mm/unuse_mm.

indeed. The FPU struct for the kernel thread isn't valid / does not
contain the expected PKRU value. So loading the pkru value from the
struct FPU does not work as expected. We could set it to 0 for a kernel
thread so we don't end up with a random value.
If we want to get this usecase working then we would have to move pkru
value from FPU to mm_struct and consider it in use_mm(). Do we want
this?

> Paolo

Sebastian