Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jim Mattson <jmattson@google.com>,
        Jacob Xu <jacobhxu@google.com>,
        Peter Shier <pshier@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Eric Biggers <ebiggers@kernel.org>
Subject: [PATCH 5.4 417/434] kvm: x86: Host feature SSBD doesnt imply guest feature AMD_SSBD
Date:   Sun, 29 Dec 2019 18:27:50 +0100
Message-Id: <20191229172730.635509330@linuxfoundation.org>
In-Reply-To: <20191229172702.393141737@linuxfoundation.org>
References: <20191229172702.393141737@linuxfoundation.org>
User-Agent: quilt/0.66
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Jim Mattson <jmattson@google.com>

commit 8715f05269bfbc6453e25e80825d781a82902f8e upstream.

The host reports support for the synthetic feature X86_FEATURE_SSBD
when any of the three following hardware features are set:
  CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31]
  CPUID.80000008H:EBX.AMD_SSBD[bit 24]
  CPUID.80000008H:EBX.VIRT_SSBD[bit 25]

Either of the first two hardware features implies the existence of the
IA32_SPEC_CTRL MSR, but CPUID.80000008H:EBX.VIRT_SSBD[bit 25] does
not. Therefore, CPUID.80000008H:EBX.AMD_SSBD[bit 24] should only be
set in the guest if CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31] or
CPUID.80000008H:EBX.AMD_SSBD[bit 24] is set on the host.

Fixes: 4c6903a0f9d76 ("KVM: x86: fix reporting of AMD speculation bug CPUID leaf")
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Jacob Xu <jacobhxu@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Reported-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/cpuid.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -760,7 +760,8 @@ static inline int __do_cpuid_func(struct
 			entry->ebx |= F(AMD_IBRS);
 		if (boot_cpu_has(X86_FEATURE_STIBP))
 			entry->ebx |= F(AMD_STIBP);
-		if (boot_cpu_has(X86_FEATURE_SSBD))
+		if (boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
+		    boot_cpu_has(X86_FEATURE_AMD_SSBD))
 			entry->ebx |= F(AMD_SSBD);
 		if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
 			entry->ebx |= F(AMD_SSB_NO);