FAILED: patch "[PATCH] kvm: x86: Use KVM CPU capabilities to determine CR4 reserved" failed to apply to 5.4-stable tree

PATCH [email protected] 1 participant 1 message May 12, 2020

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Stable branch x86 KVM x86

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2020-05-12 12:47 UTC #0 lore raw

The patch below does not apply to the 5.4-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 139f7425fdf54f054463e7524b9f54c41af8407f Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <[email protected]>
Date: Tue, 5 May 2020 09:40:46 -0400
Subject: [PATCH] kvm: x86: Use KVM CPU capabilities to determine CR4 reserved
bits

Using CPUID data can be useful for the processor compatibility check, but that's it. Using it to compute guest-reserved bits can have both false positives (such as LA57 and UMIP which we are already handling) and false negatives: in particular, with this patch we don't allow anymore a KVM guest to set CR4.PKE when CR4.PKE is clear on the host.

Fixes b9dd21e104bc ("KVM: x86: simplify handling of PKRU")

Reported-by Jim Mattson <[email protected]>

Tested-by Jim Mattson <[email protected]>

Signed-off-by Paolo Bonzini <[email protected]>

arch/x86/kvm/x86.c +5 ~~-15~~

index c5835f9cb9ad..8d296e3d0d56 100644
@@ -926,19 +926,6 @@ EXPORT_SYMBOL_GPL(kvm_set_xcr);
 	__reserved_bits;				\
 })
 
-static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c)
-{
-	u64 reserved_bits = __cr4_reserved_bits(cpu_has, c);
-
-	if (kvm_cpu_cap_has(X86_FEATURE_LA57))
-		reserved_bits &= ~X86_CR4_LA57;
-
-	if (kvm_cpu_cap_has(X86_FEATURE_UMIP))
-		reserved_bits &= ~X86_CR4_UMIP;
-
-	return reserved_bits;
-}
-
 static int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 {
 	if (cr4 & cr4_reserved_bits)

@@ -9675,7 +9662,9 @@ int kvm_arch_hardware_setup(void *opaque)
 	if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
 		supported_xss = 0;
 
-	cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data);
+#define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
+	cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
+#undef __kvm_cpu_cap_has
 
 	if (kvm_has_tsc_control) {
 		/*

@@ -9707,7 +9696,8 @@ int kvm_arch_check_processor_compat(void *opaque)
 
 	WARN_ON(!irqs_disabled());
 
-	if (kvm_host_cr4_reserved_bits(c) != cr4_reserved_bits)
+	if (__cr4_reserved_bits(cpu_has, c) !=
+	    __cr4_reserved_bits(cpu_has, &boot_cpu_data))
 		return -EIO;
 
 	return ops->check_processor_compatibility();