Commit acfad336 authored Mar 02, 2020 by Sean Christopherson Committed by Paolo Bonzini Mar 16, 2020

KVM: x86: Drop redundant boot cpu checks on SSBD feature bits



Drop redundant checks when "emulating" SSBD feature across vendors,
i.e. advertising the AMD variant when running on an Intel CPU and vice
versa.  Both SPEC_CTRL_SSBD and AMD_SSBD are already defined in the
leaf-specific feature masks and are *not* forcefully set by the kernel,
i.e. will already be set in the entry when supported by the host.

Functionally, this changes nothing, but the redundant check is
confusing, especially when considering future patches that will further
differentiate between "real" and "emulated" feature bits.

No functional change intended.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent aceac6e5

arch/x86/kvm/cpuid.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -405,8 +405,7 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry)
		entry->edx \|= F(SPEC_CTRL);
		if (boot_cpu_has(X86_FEATURE_STIBP))
		entry->edx \|= F(INTEL_STIBP);
		if (boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) \|\|
		boot_cpu_has(X86_FEATURE_AMD_SSBD))
		if (boot_cpu_has(X86_FEATURE_AMD_SSBD))
		entry->edx \|= F(SPEC_CTRL_SSBD);
		/*
		* We emulate ARCH_CAPABILITIES in software even
		@@ -780,8 +779,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
		entry->ebx \|= F(AMD_IBRS);
		if (boot_cpu_has(X86_FEATURE_STIBP))
		entry->ebx \|= F(AMD_STIBP);
		if (boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) \|\|
		boot_cpu_has(X86_FEATURE_AMD_SSBD))
		if (boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD))
		entry->ebx \|= F(AMD_SSBD);
		if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
		entry->ebx \|= F(AMD_SSB_NO);

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