From dfb4f495856bf7875a60446b200f3f2e73ff0efd Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Wed, 30 Jun 2021 21:02:59 +0800
Subject: [PATCH] x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is
supported
stable inclusion
from linux-4.19.191
commit bd1b3b2bd4dae57e5a2e06c340531137af633368
--------------------------------
commit b6b4fbd90b155a0025223df2c137af8a701d53b3 upstream.
Initialize MSR_TSC_AUX with CPU node information if RDTSCP or RDPID is
supported. This fixes a bug where vdso_read_cpunode() will read garbage
via RDPID if RDPID is supported but RDTSCP is not. While no known CPU
supports RDPID but not RDTSCP, both Intel's SDM and AMD's APM allow for
RDPID to exist without RDTSCP, e.g. it's technically a legal CPU model
for a virtual machine.
Note, technically MSR_TSC_AUX could be initialized if and only if RDPID
is supported since RDTSCP is currently not used to retrieve the CPU node.
But, the cost of the superfluous WRMSR is negigible, whereas leaving
MSR_TSC_AUX uninitialized is just asking for future breakage if someone
decides to utilize RDTSCP.
Fixes: a582c540ac1b ("x86/vdso: Use RDPID in preference to LSL when available")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210504225632.1532621-2-seanjc@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
arch/x86/entry/vdso/vma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 5b8b556dbb12..46caca4d9141 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -343,7 +343,7 @@ static void vgetcpu_cpu_init(void *arg)
#ifdef CONFIG_NUMA
node = cpu_to_node(cpu);
#endif
- if (static_cpu_has(X86_FEATURE_RDTSCP))
+ if (boot_cpu_has(X86_FEATURE_RDTSCP) || boot_cpu_has(X86_FEATURE_RDPID))
write_rdtscp_aux((node << 12) | cpu);
/*
--
GitLab