Re: [Xen-devel] [PATCH SpectreV1+L1TF v7 4/9] nospec: introduce evaluate_nospec

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.02.19 at 09:16, <nmanthey@xxxxxxxxx> wrote:
> --- /dev/null
> +++ b/xen/include/asm-x86/nospec.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved. */
> +
> +#ifndef _ASM_X86_NOSPEC_H
> +#define _ASM_X86_NOSPEC_H
> +
> +#include <asm/alternative.h>
> +
> +/* Allow to insert a read memory barrier into conditionals */
> +static always_inline bool barrier_nospec_true(void)
> +{
> +#ifdef CONFIG_HVM
> +    alternative("", "lfence", X86_FEATURE_SC_L1TF_VULN);
> +#endif
> +    return true;
> +}
> +
> +/* Allow to protect evaluation of conditionasl with respect to speculation */
> +#ifdef CONFIG_HVM
> +#define evaluate_nospec(condition)                                         \
> +    ((condition) ? barrier_nospec_true() : !barrier_nospec_true())
> +#else
> +#define evaluate_nospec(condition) (condition)
> +#endif
> +
> +/* Allow to block speculative execution in generic code */
> +#define block_speculation() ((void)barrier_nospec_true())

Seeing Julien's request for switching to inline functions on the Arm side,
is there anything preventing these two to become inline functions too?

Jan



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