Skip to contentSkip to conversation

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

PATCH [email protected] 2 participants 2 messages Dec 29, 2019 – Jan 2, 2020

Subsystems (3)
Stable branch x86 KVM x86
lore
Share & tools
lore

[email protected]

author maintainer
#0 lore raw

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 <[email protected]>.

thanks,

greg k-h

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

From 396d2e878f92ec108e4293f1c77ea3bc90b414ff Mon Sep 17 00:00:00 2001
From: Jim Mattson <[email protected]>
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 <[email protected]>
Reviewed-by Jacob Xu <[email protected]>
Reviewed-by Peter Shier <[email protected]>
Cc Paolo Bonzini <[email protected]>
Cc [email protected]
Reported-by Eric Biggers <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>
arch/x86/kvm/cpuid.c +2 -1
index c0aa07487eb8..dd18aa6fa317 100644
@@ -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
maintainer
#1 lore raw
Quoted 30 lines · On Sun, Dec 29, 2019 at 04:51:06PM +0100, [email protected] 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 <[email protected]>.

thanks,

greg k-h

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

From 396d2e878f92ec108e4293f1c77ea3bc90b414ff Mon Sep 17 00:00:00 2001
From: Jim Mattson <[email protected]>
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.

Quoted 8 lines
Fixes 0c54914d0c52a ("KVM: x86: use Intel speculation bugs and features as derived in generic x86 code")
Signed-off-by Jim Mattson <[email protected]>
Reviewed-by Jacob Xu <[email protected]>
Reviewed-by Peter Shier <[email protected]>
Cc Paolo Bonzini <[email protected]>
Cc [email protected]
Reported-by Eric Biggers <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>

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

Signature · 2 lines
Thanks,
Sasha