FAILED: patch "[PATCH] x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b6b4fbd90b155a0025223df2c137af8a701d53b3 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <[email protected]>
Date: Tue, 4 May 2021 15:56:31 -0700
Subject: [PATCH] x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is
supported

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.

index 6bdb69a9a7dc..490bed07fe35 100644
@@ -1851,7 +1851,7 @@ 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. */

From: Sean Christopherson <[email protected]>

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 ]

---
 arch/x86/entry/vdso/vma.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

---

@@ -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);
 
 	/*

Now queued up, thanks!

greg k-h