From: Fenghua Yu <fenghua.yu@intel.com>
To: "Thomas Gleixner" <tglx@linutronix.de>,
"Borislav Petkov" <bp@alien8.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Tony Luck" <tony.luck@intel.com>,
"Christopherson Sean J" <sean.j.christopherson@intel.com>,
"Ashok Raj" <ashok.raj@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 RFC v3 1/4] x86/cpufeatures: Enumerate #DB for bus lock detection
Date: Sat, 31 Oct 2020 00:27:11 +0000 [thread overview]
Message-ID: <20201031002714.3649728-2-fenghua.yu@intel.com> (raw)
In-Reply-To: <20201031002714.3649728-1-fenghua.yu@intel.com>
A bus lock is acquired either through split locked access to
writeback (WB) memory or by using locks to uncacheable (UC) memory
(e.g. direct device assignment). This is typically >1000 cycles slower
than an atomic operation within a cache line. It also disrupts performance
on other cores.
Some CPUs have 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 mitigations.
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>
---
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 dad350d42ecf..f375d9cb8123 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -352,6 +352,7 @@
#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 */
--
2.29.1
next prev parent reply other threads:[~2020-10-31 0:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-31 0:27 [PATCH RFC v3 0/4] x86/bus_lock: Enable bus lock detection Fenghua Yu
2020-10-31 0:27 ` Fenghua Yu [this message]
2020-10-31 0:27 ` [PATCH RFC v3 2/4] x86/bus_lock: Handle warn and fatal in #DB for bus lock Fenghua Yu
2020-11-03 12:15 ` Xiaoyao Li
2020-11-06 20:31 ` Fenghua Yu
2020-10-31 0:27 ` [PATCH RFC v3 3/4] x86/bus_lock: Set rate limit " Fenghua Yu
2020-10-31 0:27 ` [PATCH RFC v3 4/4] Documentation/admin-guide: Change doc for split_lock_detect parameter Fenghua Yu
2020-10-31 3:14 ` Randy Dunlap
2020-11-02 17:03 ` Fenghua Yu
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