From: Fenghua Yu <fenghua.yu@intel.com>
To: "Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Peter Zijlstra" <peterz@infradead.org>,
"Tony Luck" <tony.luck@intel.com>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Xiaoyao Li " <xiaoyao.li@intel.com>,
"Ravi V Shankar" <ravi.v.shankar@intel.com>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>,
"x86" <x86@kernel.org>, Fenghua Yu <fenghua.yu@intel.com>
Subject: [PATCH v6 1/3] x86/cpufeatures: Enumerate #DB for bus lock detection
Date: Mon, 22 Mar 2021 13:53:23 +0000 [thread overview]
Message-ID: <20210322135325.682257-2-fenghua.yu@intel.com> (raw)
In-Reply-To: <20210322135325.682257-1-fenghua.yu@intel.com>
A bus lock is acquired through either a split locked access to
writeback (WB) memory or any locked access to non-WB memory. This is
typically >1000 cycles slower than an atomic operation within a cache
line. It also disrupts performance on other cores.
Some CPUs have the ability to notify the kernel by an #DB trap after a user
instruction acquires a bus lock and is executed. This allows the kernel
to enforce user application throttling or mitigation. Both breakpoint
and bus lock can trigger the #DB trap in the same instruction and the
ordering of handling them is the kernel #DB handler's choice.
The CPU feature flag to be shown in /proc/cpuinfo will be "bus_lock_detect".
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
Change Log:
v6:
- Fix wording issues in the commit message (Thomas).
v5:
- Add "Both breakpoint and bus lock can trigger an #DB trap..." in the
commit message (Thomas).
arch/x86/include/asm/cpufeatures.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index cc96e26d69f7..faec3d92d09b 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -354,6 +354,7 @@
#define X86_FEATURE_AVX512_VPOPCNTDQ (16*32+14) /* POPCNT for vectors of DW/QW */
#define X86_FEATURE_LA57 (16*32+16) /* 5-level page tables */
#define X86_FEATURE_RDPID (16*32+22) /* RDPID instruction */
+#define X86_FEATURE_BUS_LOCK_DETECT (16*32+24) /* Bus Lock detect */
#define X86_FEATURE_CLDEMOTE (16*32+25) /* CLDEMOTE instruction */
#define X86_FEATURE_MOVDIRI (16*32+27) /* MOVDIRI instruction */
#define X86_FEATURE_MOVDIR64B (16*32+28) /* MOVDIR64B instruction */
--
2.31.0
next prev parent reply other threads:[~2021-03-22 13:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 13:53 [PATCH v6 0/3] x86/bus_lock: Enable bus lock detection Fenghua Yu
2021-03-22 13:53 ` Fenghua Yu [this message]
2021-03-28 21:32 ` [tip: x86/splitlock] x86/cpufeatures: Enumerate #DB for " tip-bot2 for Fenghua Yu
2021-03-22 13:53 ` [PATCH v6 2/3] x86/bus_lock: Handle #DB for bus lock Fenghua Yu
2021-03-28 21:32 ` [tip: x86/splitlock] x86/traps: " tip-bot2 for Fenghua Yu
2021-03-22 13:53 ` [PATCH v6 3/3] Documentation/admin-guide: Change doc for split_lock_detect parameter Fenghua Yu
2021-03-28 21:32 ` [tip: x86/splitlock] " tip-bot2 for Fenghua Yu
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