linux-kernel - Re: [PATCH v2 08/23] x86/fpu: Provide fpu_update_guest_perm

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Message-ID: <87wnk3awwf.ffs@tglx>
Date:   Fri, 17 Dec 2021 19:50:24 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jing Liu <jing2.liu@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        pbonzini@...hat.com
Cc:     seanjc@...gle.com, jun.nakajima@...el.com, kevin.tian@...el.com,
        jing2.liu@...ux.intel.com, jing2.liu@...el.com,
        guang.zeng@...el.com, wei.w.wang@...el.com, yang.zhong@...el.com
Subject: Re: [PATCH v2 08/23] x86/fpu: Provide
 fpu_update_guest_perm_features() for guest

eviewed-by: Thomas Gleixner <tglx@...utronix.de>
On Fri, Dec 17 2021 at 07:29, Jing Liu wrote:
> +/*
> + * fpu_update_guest_perm_features - Enable xfeatures according to guest perm
> + * @guest_fpu:		Pointer to the guest FPU container
> + *
> + * Enable all dynamic xfeatures according to guest perm. Invoked if the
> + * caller wants to conservatively expand fpstate buffer instead of waiting
> + * until XCR0 or XFD MSR is written.
> + *
> + * Return: 0 on success, error code otherwise
> + */
> +int fpu_update_guest_perm_features(struct fpu_guest *guest_fpu)
> +{
> +	u64 expand;
> +
> +	lockdep_assert_preemption_enabled();
> +
> +	if (!IS_ENABLED(CONFIG_X86_64))
> +		return 0;
> +
> +	expand = guest_fpu->perm & ~guest_fpu->xfeatures;
> +	if (!expand)
> +		return 0;
> +
> +	return __xfd_enable_feature(expand, guest_fpu);
> +}
> +EXPORT_SYMBOL_GPL(fpu_update_guest_perm_features);

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>