linux-kernel - [PATCH RFC rebase 1/9] powerpc: Add barrier

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Message-Id: <8cb7d41beef9bdd351120d0512f73ac3bfada168.1521141122.git.msuchanek@suse.de>
Date:   Thu, 15 Mar 2018 20:15:50 +0100
From:   Michal Suchanek <msuchanek@...e.de>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     Kate Stewart <kstewart@...uxfoundation.org>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Neuling <mikey@...ling.org>,
        "Bryant G. Ly" <bryantly@...ux.vnet.ibm.com>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Daniel Axtens <dja@...ens.net>,
        Nicholas Piggin <npiggin@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Gibson <david@...son.dropbear.id.au>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Cédric Le Goater <clg@...d.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Joe Perches <joe@...ches.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Tobin C. Harding" <me@...in.cc>,
        Michal Suchanek <msuchanek@...e.de>
Subject: [PATCH RFC rebase 1/9] powerpc: Add barrier_nospec

When the firmware supports it an otherwise useless combination of ORI
instruction arguments is interpreted as speculation barrier. Implement
barrier_nospec using this instruction.

Based on the out-of-tree gmb() implementation.

Signed-off-by: Michal Suchanek <msuchanek@...e.de>
---
 arch/powerpc/include/asm/barrier.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h
index 10daa1d56e0a..8e47b3abe405 100644
--- a/arch/powerpc/include/asm/barrier.h
+++ b/arch/powerpc/include/asm/barrier.h
@@ -75,6 +75,15 @@ do {									\
 	___p1;								\
 })
 
+/* TODO: add patching so this can be disabled */
+/* Prevent speculative execution past this barrier. */
+#define barrier_nospec_asm ori 31,31,0
+#ifdef __ASSEMBLY__
+#define barrier_nospec barrier_nospec_asm
+#else
+#define barrier_nospec() __asm__ __volatile__ (stringify_in_c(barrier_nospec_asm) : : :)
+#endif
+
 #include <asm-generic/barrier.h>
 
 #endif /* _ASM_POWERPC_BARRIER_H */
-- 
2.13.6