linux-kernel - Re: [PATCH 15/22] x86/entry: Add TIF_NEED_FPU

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Message-ID: <20190214152814.dptm4edcpfn7vrff@linutronix.de>
Date:   Thu, 14 Feb 2019 16:28:14 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 15/22] x86/entry: Add TIF_NEED_FPU_LOAD

On 2019-02-13 10:35:53 [+0100], Borislav Petkov wrote:
…
> > + *
> > + * If TIF_NEED_FPU_LOAD is cleared then CPU's FPU registers are holding the
> > + * current content of current()'s FPU register state.
> 
> "current content of current" - that's a lot of c...
> 
> Make that
> 
> "... then the CPU's FPU registers are mirrored in the current thread's
> FPU registers state."

Replaced `mirrored' with saved:

+ * If TIF_NEED_FPU_LOAD is cleared then the CPU's FPU registers are saved in
+ * the current thread's FPU registers state.
+ * If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not hold current()'s
+ * FPU registers. It is required to load the registers before returning to
+ * userland or using the content otherwise.

Sebastian