From: Thomas Gleixner <tglx@linutronix.de>
To: gregkh@linuxfoundation.org, seanjc@google.com
Cc: stable@vger.kernel.org
Subject: [PATCH] x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is supported
Date: Wed, 12 May 2021 12:08:00 +0200 [thread overview]
Message-ID: <875yzofenz.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1620632578184221@kroah.com>
From: Sean Christopherson <seanjc@google.com>
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.
[ tglx: Backport for 4.14/4.19 ]
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
---
arch/x86/entry/vdso/vma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
---
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -342,7 +342,7 @@ 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);
/*
next prev parent reply other threads:[~2021-05-12 10:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-10 7:42 FAILED: patch "[PATCH] x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is" failed to apply to 4.4-stable tree gregkh
2021-05-12 10:08 ` Thomas Gleixner [this message]
2021-05-12 10:10 ` [PATCH] x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is supported Greg KH
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