FAILED: patch "[PATCH] kvm: x86: Host feature SSBD doesn't imply guest feature" failed to apply to 4.19-stable tree

FAILED: patch "[PATCH] kvm: x86: Host feature SSBD doesn't imply guest feature" failed to apply to 4.19-stable tree

[gregkh]

The patch below does not apply to the 4.19-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 <stable@vger.kernel.org>.

thanks,

greg k-h

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

From 396d2e878f92ec108e4293f1c77ea3bc90b414ff Mon Sep 17 00:00:00 2001
From: Jim Mattson <jmattson@google.com>
Date: Fri, 13 Dec 2019 16:15:15 -0800
Subject: [PATCH] kvm: x86: Host feature SSBD doesn't imply guest feature
 SPEC_CTRL_SSBD

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.(EAX=7,ECX=0):EDX.SSBD[bit 31] 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: 0c54914d0c52a ("KVM: x86: use Intel speculation bugs and features as derived in generic x86 code")
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>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index c0aa07487eb8..dd18aa6fa317 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -402,7 +402,8 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
 			entry->edx |= F(SPEC_CTRL);
 		if (boot_cpu_has(X86_FEATURE_STIBP))
 			entry->edx |= F(INTEL_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->edx |= F(SPEC_CTRL_SSBD);
 		/*
 		 * We emulate ARCH_CAPABILITIES in software even

Re: FAILED: patch "[PATCH] kvm: x86: Host feature SSBD doesn't imply guest feature" failed to apply to 4.19-stable tree

[Sasha Levin]

On Sun, Dec 29, 2019 at 04:51:06PM +0100, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 4.19-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 <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From 396d2e878f92ec108e4293f1c77ea3bc90b414ff Mon Sep 17 00:00:00 2001
>From: Jim Mattson <jmattson@google.com>
>Date: Fri, 13 Dec 2019 16:15:15 -0800
>Subject: [PATCH] kvm: x86: Host feature SSBD doesn't imply guest feature
> SPEC_CTRL_SSBD
>
>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.(EAX=7,ECX=0):EDX.SSBD[bit 31] 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: 0c54914d0c52a ("KVM: x86: use Intel speculation bugs and features as derived in generic x86 code")
>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>

I don't think that this is needed on 4.19 and older, but it would be
nice if someone would ack.

-- 
Thanks,
Sasha