From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Will Deacon <will@kernel.org>, Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Sami Tolvanen <samitolvanen@google.com>,
Masahiro Yamada <masahiroy@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH v4 3/4] arm64: alternatives: Remove READ_ONCE() usage during patch operation
Date: Tue, 3 Nov 2020 12:17:20 +0000 [thread overview]
Message-ID: <20201103121721.5166-4-will@kernel.org> (raw)
In-Reply-To: <20201103121721.5166-1-will@kernel.org>
In preparation for patching the internals of READ_ONCE() itself, replace
its usage on the alternatives patching patch with a volatile variable
instead.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/alternative.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index 73039949b5ce..a57cffb752e8 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -21,7 +21,8 @@
#define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset)
#define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset)
-static int all_alternatives_applied;
+/* Volatile, as we may be patching the guts of READ_ONCE() */
+static volatile int all_alternatives_applied;
static DECLARE_BITMAP(applied_alternatives, ARM64_NCAPS);
@@ -205,7 +206,7 @@ static int __apply_alternatives_multi_stop(void *unused)
/* We always have a CPU 0 at this point (__init) */
if (smp_processor_id()) {
- while (!READ_ONCE(all_alternatives_applied))
+ while (!all_alternatives_applied)
cpu_relax();
isb();
} else {
@@ -217,7 +218,7 @@ static int __apply_alternatives_multi_stop(void *unused)
BUG_ON(all_alternatives_applied);
__apply_alternatives(®ion, false, remaining_capabilities);
/* Barriers provided by the cache flushing */
- WRITE_ONCE(all_alternatives_applied, 1);
+ all_alternatives_applied = 1;
}
return 0;
--
2.29.1.341.ge80a0c044ae-goog
next prev parent reply other threads:[~2020-11-03 12:17 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-03 12:17 [PATCH v4 0/4] Upgrade READ_ONCE() to RCpc acquire on arm64 with LTO Will Deacon
2020-11-03 12:17 ` [PATCH v4 1/4] arm64: alternatives: Split up alternative.h Will Deacon
2020-11-03 12:40 ` Mark Rutland
2020-11-03 12:42 ` Will Deacon
2020-11-03 12:17 ` [PATCH v4 2/4] arm64: cpufeatures: Add capability for LDAPR instruction Will Deacon
2020-11-03 12:44 ` Mark Rutland
2020-11-03 12:17 ` Will Deacon [this message]
2020-11-03 12:46 ` [PATCH v4 3/4] arm64: alternatives: Remove READ_ONCE() usage during patch operation Mark Rutland
2020-11-03 12:17 ` [PATCH v4 4/4] arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y Will Deacon
2020-11-03 12:58 ` Mark Rutland
2020-11-03 13:13 ` Will Deacon
2020-11-09 23:25 ` [PATCH v4 0/4] Upgrade READ_ONCE() to RCpc acquire on arm64 with LTO Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201103121721.5166-4-will@kernel.org \
--to=will@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=keescook@chromium.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=masahiroy@kernel.org \
--cc=peterz@infradead.org \
--cc=samitolvanen@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).