linux-kernel - Re: [PATCH v3 10/21] x86/fpu/xstate: Update xstate save function to support dynamic xstate

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Date:   Mon, 8 Feb 2021 13:33:59 +0100
From:   Borislav Petkov <bp@...e.de>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>
Cc:     luto@...nel.org, tglx@...utronix.de, mingo@...nel.org,
        x86@...nel.org, len.brown@...el.com, dave.hansen@...el.com,
        jing2.liu@...el.com, ravi.v.shankar@...el.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v3 10/21] x86/fpu/xstate: Update xstate save function to
 support dynamic xstate

On Wed, Dec 23, 2020 at 07:57:06AM -0800, Chang S. Bae wrote:
> copy_xregs_to_kernel() used to save all user states in a kernel buffer.
> When the dynamic user state is enabled, it becomes conditional which state
> to be saved.
> 
> fpu->state_mask can indicate which state components are reserved to be
> saved in XSAVE buffer. Use it as XSAVE's instruction mask to select states.
> 
> KVM used to save all xstate via copy_xregs_to_kernel(). Update KVM to set a
> valid fpu->state_mask, which will be necessary to correctly handle dynamic
> state buffers.

All this commit message should say is something along the lines of
"extend copy_xregs_to_kernel() to receive a mask argument of which
states to save, in preparation of dynamic states handling."

> No functional change until the kernel supports dynamic user states.

Same comment as before.

-- 
Regards/Gruss,
    Boris.

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