linux-kernel - [RFC PATCH 1/2] nospec: Add a generic barrier

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Message-Id: <a29745ae921ed03084b7d4bdec38c7b01d764fb9.1666651511.git.pawan.kumar.gupta@linux.intel.com>
Date:   Mon, 24 Oct 2022 15:57:46 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     scott.d.constable@...el.com, daniel.sneddon@...ux.intel.com,
        Jakub Kicinski <kuba@...nel.org>, dave.hansen@...el.com,
        Johannes Berg <johannes@...solutions.net>,
        Paolo Abeni <pabeni@...hat.com>,
        antonio.gomez.iglesias@...ux.intel.com,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, gregkh@...uxfoundation.org, netdev@...r.kernel.org
Subject: [RFC PATCH 1/2] nospec: Add a generic barrier_nospec()

barrier_nospec() is a speculation barrier with an arch dependent
implementation. Architectures that don't need a speculation barrier
shouldn't have to define an arch specific version.

To be able to use barrier_nospec() in non-architecture code add a
generic version that does nothing. Architectures needing speculation
barrier can override the generic version in their asm/barrier.h.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
---
 include/linux/nospec.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/nospec.h b/include/linux/nospec.h
index c1e79f72cd89..60e040a5df27 100644
--- a/include/linux/nospec.h
+++ b/include/linux/nospec.h
@@ -60,6 +60,10 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
 	(typeof(_i)) (_i & _mask);					\
 })
 
+#ifndef barrier_nospec
+#define barrier_nospec()	do { } while (0)
+#endif
+
 /* Speculation control prctl */
 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which);
 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
-- 
2.37.3