[PATCH 4.4 60/88] x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP

Greg Kroah-Hartman
2018-12-14T12:18:18Z

From: Borislav Petkov <bp@suse.de>

commit e7c587da125291db39ddf1f49b18e5970adbac17 upstream.

Intel and AMD have different CPUID bits hence for those use synthetic bits
which get set on the respective vendor's in init_speculation_control(). So
that debacles like what the commit message of

c65732e4f721 ("x86/cpu: Restore CPUID_8000_0008_EBX reload")

talks about don't happen anymore.

Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Jörg Otte <jrg.otte@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20180504161815.GG9257@pd.tnic
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 4.4: This was partly applied before; apply just the
missing bits]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/cpuid.c | 10 +++++-----
arch/x86/kvm/cpuid.h | 4 ++--
2 files changed, 7 insertions(+), 7 deletions(-)

--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -343,7 +343,7 @@ static inline int __do_cpuid_ent(struct

/* cpuid 0x80000008.ebx */
const u32 kvm_cpuid_8000_0008_ebx_x86_features =
- F(IBPB) | F(IBRS);
+ F(AMD_IBPB) | F(AMD_IBRS);

/* cpuid 0xC0000001.edx */
const u32 kvm_supported_word5_x86_features =
@@ -596,10 +596,10 @@ static inline int __do_cpuid_ent(struct
entry->eax = g_phys_as | (virt_as << 8);
entry->edx = 0;
/* IBRS and IBPB aren't necessarily present in hardware cpuid */
- if (boot_cpu_has(X86_FEATURE_IBPB))
- entry->ebx |= F(IBPB);
- if (boot_cpu_has(X86_FEATURE_IBRS))
- entry->ebx |= F(IBRS);
+ if (boot_cpu_has(X86_FEATURE_AMD_IBPB))
+ entry->ebx |= F(AMD_IBPB);
+ if (boot_cpu_has(X86_FEATURE_AMD_IBRS))
+ entry->ebx |= F(AMD_IBRS);
entry->ebx &= kvm_cpuid_8000_0008_ebx_x86_features;
cpuid_mask(&entry->ebx, CPUID_8000_0008_EBX);
break;
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -164,7 +164,7 @@ static inline bool guest_cpuid_has_ibpb(
struct kvm_cpuid_entry2 *best;

best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
- if (best && (best->ebx & bit(X86_FEATURE_IBPB)))
+ if (best && (best->ebx & bit(X86_FEATURE_AMD_IBPB)))
return true;
best = kvm_find_cpuid_entry(vcpu, 7, 0);
return best && (best->edx & bit(X86_FEATURE_SPEC_CTRL));
@@ -175,7 +175,7 @@ static inline bool guest_cpuid_has_spec_
struct kvm_cpuid_entry2 *best;

best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
- if (best && (best->ebx & bit(X86_FEATURE_IBRS)))
+ if (best && (best->ebx & bit(X86_FEATURE_AMD_IBRS)))
return true;
best = kvm_find_cpuid_entry(vcpu, 7, 0);
return best && (best->edx & (bit(X86_FEATURE_SPEC_CTRL) | bit(X86_FEATURE_SPEC_CTRL_SSBD)));