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Subject[GIT pull] x86/pti updates for 4.18
Linus,

please pull the latest x86-pti-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-pti-for-linus

Three small commits updating the SSB mitigation to take the updated AMD
mitigation variants into account.

Thanks,

tglx

------------------>
Konrad Rzeszutek Wilk (3):
x86/bugs: Add AMD's variant of SSB_NO
x86/bugs: Add AMD's SPEC_CTRL MSR usage
x86/bugs: Switch the selection of mitigation from CPU vendor to CPU features


arch/x86/include/asm/cpufeatures.h | 2 ++
arch/x86/kernel/cpu/bugs.c | 13 +++++--------
arch/x86/kernel/cpu/common.c | 9 ++++++++-
arch/x86/kvm/cpuid.c | 10 ++++++++--
arch/x86/kvm/svm.c | 8 +++++---
5 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index fb00a2fca990..5701f5cecd31 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -282,7 +282,9 @@
#define X86_FEATURE_AMD_IBPB (13*32+12) /* "" Indirect Branch Prediction Barrier */
#define X86_FEATURE_AMD_IBRS (13*32+14) /* "" Indirect Branch Restricted Speculation */
#define X86_FEATURE_AMD_STIBP (13*32+15) /* "" Single Thread Indirect Branch Predictors */
+#define X86_FEATURE_AMD_SSBD (13*32+24) /* "" Speculative Store Bypass Disable */
#define X86_FEATURE_VIRT_SSBD (13*32+25) /* Virtualized Speculative Store Bypass Disable */
+#define X86_FEATURE_AMD_SSB_NO (13*32+26) /* "" Speculative Store Bypass is fixed in hardware. */

/* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */
#define X86_FEATURE_DTHERM (14*32+ 0) /* Digital Thermal Sensor */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 7416fc206b4a..cd0fda1fff6d 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -529,18 +529,15 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void)
if (mode == SPEC_STORE_BYPASS_DISABLE) {
setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE);
/*
- * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD uses
- * a completely different MSR and bit dependent on family.
+ * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may
+ * use a completely different MSR and bit dependent on family.
*/
- switch (boot_cpu_data.x86_vendor) {
- case X86_VENDOR_INTEL:
+ if (!static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
+ x86_amd_ssb_disable();
+ else {
x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
x86_spec_ctrl_mask |= SPEC_CTRL_SSBD;
wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
- break;
- case X86_VENDOR_AMD:
- x86_amd_ssb_disable();
- break;
}
}

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 95c8e507580d..910b47ee8078 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -803,6 +803,12 @@ static void init_speculation_control(struct cpuinfo_x86 *c)
set_cpu_cap(c, X86_FEATURE_STIBP);
set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL);
}
+
+ if (cpu_has(c, X86_FEATURE_AMD_SSBD)) {
+ set_cpu_cap(c, X86_FEATURE_SSBD);
+ set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL);
+ clear_cpu_cap(c, X86_FEATURE_VIRT_SSBD);
+ }
}

void get_cpu_cap(struct cpuinfo_x86 *c)
@@ -992,7 +998,8 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);

if (!x86_match_cpu(cpu_no_spec_store_bypass) &&
- !(ia32_cap & ARCH_CAP_SSB_NO))
+ !(ia32_cap & ARCH_CAP_SSB_NO) &&
+ !cpu_has(c, X86_FEATURE_AMD_SSB_NO))
setup_force_cpu_bug(X86_BUG_SPEC_STORE_BYPASS);

if (x86_match_cpu(cpu_no_meltdown))
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 92bf2f2e7cdd..f4f30d0c25c4 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -379,7 +379,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,

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

/* cpuid 0xC0000001.edx */
const u32 kvm_cpuid_C000_0001_edx_x86_features =
@@ -664,7 +665,12 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
entry->ebx |= F(VIRT_SSBD);
entry->ebx &= kvm_cpuid_8000_0008_ebx_x86_features;
cpuid_mask(&entry->ebx, CPUID_8000_0008_EBX);
- if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD))
+ /*
+ * The preference is to use SPEC CTRL MSR instead of the
+ * VIRT_SPEC MSR.
+ */
+ if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
+ !boot_cpu_has(X86_FEATURE_AMD_SSBD))
entry->ebx |= F(VIRT_SSBD);
break;
}
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 26110c202b19..950ec50f77c3 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4115,7 +4115,8 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
break;
case MSR_IA32_SPEC_CTRL:
if (!msr_info->host_initiated &&
- !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS))
+ !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
return 1;

msr_info->data = svm->spec_ctrl;
@@ -4217,11 +4218,12 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
break;
case MSR_IA32_SPEC_CTRL:
if (!msr->host_initiated &&
- !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS))
+ !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
return 1;

/* The STIBP bit doesn't fault even if it's not advertised */
- if (data & ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP))
+ if (data & ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP | SPEC_CTRL_SSBD))
return 1;

svm->spec_ctrl = data;
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