linux-kernel - [PATCH 12/61] KVM: x86: Drop redundant boot cpu checks on SSBD feature bits

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Message-Id: <20200201185218.24473-13-sean.j.christopherson@intel.com>
Date:   Sat,  1 Feb 2020 10:51:29 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 12/61] KVM: x86: Drop redundant boot cpu checks on SSBD feature bits

Drop redundnant 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.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/cpuid.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index fd04f17d1836..52f0af4e10d5 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -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);
-- 
2.24.1