This is a note to let you know that I've just added the patch titled x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is supported to the 5.12-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-cpu-initialize-msr_tsc_aux-if-rdtscp-or-rdpid-is-supported.patch and it can be found in the queue-5.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From b6b4fbd90b155a0025223df2c137af8a701d53b3 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc@xxxxxxxxxx> Date: Tue, 4 May 2021 15:56:31 -0700 Subject: x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is supported From: Sean Christopherson <seanjc@xxxxxxxxxx> 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@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/20210504225632.1532621-2-seanjc@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/cpu/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1850,7 +1850,7 @@ static inline void setup_getcpu(int cpu) unsigned long cpudata = vdso_encode_cpunode(cpu, early_cpu_to_node(cpu)); struct desc_struct d = { }; - if (boot_cpu_has(X86_FEATURE_RDTSCP)) + if (boot_cpu_has(X86_FEATURE_RDTSCP) || boot_cpu_has(X86_FEATURE_RDPID)) write_rdtscp_aux(cpudata); /* Store CPU and node number in limit. */ Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are queue-5.12/x86-cpu-initialize-msr_tsc_aux-if-rdtscp-or-rdpid-is-supported.patch