diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0026-x86-bugs-KVM-Support-the-combination-of-guest-and-ho.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0026-x86-bugs-KVM-Support-the-combination-of-guest-and-ho.patch | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0026-x86-bugs-KVM-Support-the-combination-of-guest-and-ho.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0026-x86-bugs-KVM-Support-the-combination-of-guest-and-ho.patch new file mode 100644 index 00000000..d0e8ddcb --- /dev/null +++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0026-x86-bugs-KVM-Support-the-combination-of-guest-and-ho.patch @@ -0,0 +1,137 @@ +From d9dc73cbf12047f0d0e171366bfb962b3a592e6f Mon Sep 17 00:00:00 2001 +From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> +Date: Wed, 25 Apr 2018 22:04:19 -0400 +Subject: [PATCH 26/93] x86/bugs, KVM: Support the combination of guest and + host IBRS + +commit 5cf687548705412da47c9cec342fd952d71ed3d5 upstream + +A guest may modify the SPEC_CTRL MSR from the value used by the +kernel. Since the kernel doesn't use IBRS, this means a value of zero is +what is needed in the host. + +But the 336996-Speculative-Execution-Side-Channel-Mitigations.pdf refers to +the other bits as reserved so the kernel should respect the boot time +SPEC_CTRL value and use that. + +This allows to deal with future extensions to the SPEC_CTRL interface if +any at all. + +Note: This uses wrmsrl() instead of native_wrmsl(). I does not make any +difference as paravirt will over-write the callq *0xfff.. with the wrmsrl +assembler code. + +Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Reviewed-by: Borislav Petkov <bp@suse.de> +Reviewed-by: Ingo Molnar <mingo@kernel.org> +Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + arch/x86/include/asm/nospec-branch.h | 10 ++++++++++ + arch/x86/kernel/cpu/bugs.c | 18 ++++++++++++++++++ + arch/x86/kvm/svm.c | 6 ++---- + arch/x86/kvm/vmx.c | 6 ++---- + 4 files changed, 32 insertions(+), 8 deletions(-) + +diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h +index 9ec3d4d..d1c2630 100644 +--- a/arch/x86/include/asm/nospec-branch.h ++++ b/arch/x86/include/asm/nospec-branch.h +@@ -228,6 +228,16 @@ enum spectre_v2_mitigation { + extern void x86_spec_ctrl_set(u64); + extern u64 x86_spec_ctrl_get_default(void); + ++/* ++ * On VMENTER we must preserve whatever view of the SPEC_CTRL MSR ++ * the guest has, while on VMEXIT we restore the host view. This ++ * would be easier if SPEC_CTRL were architecturally maskable or ++ * shadowable for guests but this is not (currently) the case. ++ * Takes the guest view of SPEC_CTRL MSR as a parameter. ++ */ ++extern void x86_spec_ctrl_set_guest(u64); ++extern void x86_spec_ctrl_restore_host(u64); ++ + extern char __indirect_thunk_start[]; + extern char __indirect_thunk_end[]; + +diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c +index 6ff972a..f5cad2f 100644 +--- a/arch/x86/kernel/cpu/bugs.c ++++ b/arch/x86/kernel/cpu/bugs.c +@@ -122,6 +122,24 @@ u64 x86_spec_ctrl_get_default(void) + } + EXPORT_SYMBOL_GPL(x86_spec_ctrl_get_default); + ++void x86_spec_ctrl_set_guest(u64 guest_spec_ctrl) ++{ ++ if (!boot_cpu_has(X86_FEATURE_IBRS)) ++ return; ++ if (x86_spec_ctrl_base != guest_spec_ctrl) ++ wrmsrl(MSR_IA32_SPEC_CTRL, guest_spec_ctrl); ++} ++EXPORT_SYMBOL_GPL(x86_spec_ctrl_set_guest); ++ ++void x86_spec_ctrl_restore_host(u64 guest_spec_ctrl) ++{ ++ if (!boot_cpu_has(X86_FEATURE_IBRS)) ++ return; ++ if (x86_spec_ctrl_base != guest_spec_ctrl) ++ wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); ++} ++EXPORT_SYMBOL_GPL(x86_spec_ctrl_restore_host); ++ + #ifdef RETPOLINE + static bool spectre_v2_bad_module; + +diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c +index 8551a54..a07579f 100644 +--- a/arch/x86/kvm/svm.c ++++ b/arch/x86/kvm/svm.c +@@ -4905,8 +4905,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) + * is no need to worry about the conditional branch over the wrmsr + * being speculatively taken. + */ +- if (svm->spec_ctrl) +- native_wrmsrl(MSR_IA32_SPEC_CTRL, svm->spec_ctrl); ++ x86_spec_ctrl_set_guest(svm->spec_ctrl); + + asm volatile ( + "push %%" _ASM_BP "; \n\t" +@@ -5018,8 +5017,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) + if (unlikely(!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL))) + svm->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL); + +- if (svm->spec_ctrl) +- native_wrmsrl(MSR_IA32_SPEC_CTRL, 0); ++ x86_spec_ctrl_restore_host(svm->spec_ctrl); + + /* Eliminate branch target predictions from guest mode */ + vmexit_fill_RSB(); +diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c +index 273313f..c386d13 100644 +--- a/arch/x86/kvm/vmx.c ++++ b/arch/x86/kvm/vmx.c +@@ -8898,8 +8898,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) + * is no need to worry about the conditional branch over the wrmsr + * being speculatively taken. + */ +- if (vmx->spec_ctrl) +- native_wrmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl); ++ x86_spec_ctrl_set_guest(vmx->spec_ctrl); + + vmx->__launched = vmx->loaded_vmcs->launched; + asm( +@@ -9037,8 +9036,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) + if (unlikely(!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL))) + vmx->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL); + +- if (vmx->spec_ctrl) +- native_wrmsrl(MSR_IA32_SPEC_CTRL, 0); ++ x86_spec_ctrl_restore_host(vmx->spec_ctrl); + + /* Eliminate branch target predictions from guest mode */ + vmexit_fill_RSB(); +-- +2.7.4 + |