This is a note to let you know that I've just added the patch titled
KVM/x86: Remove indirect MSR op calls from SPEC_CTRL
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: kvm-x86-remove-indirect-msr-op-calls-from-spec_ctrl.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From ecb586bd29c99fb4de599dec388658e74388daad Mon Sep 17 00:00:00 2001
From: Paolo Bonzini pbonzini@redhat.com Date: Thu, 22 Feb 2018 16:43:17 +0100 Subject: KVM/x86: Remove indirect MSR op calls from SPEC_CTRL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
From: Paolo Bonzini pbonzini@redhat.com
commit ecb586bd29c99fb4de599dec388658e74388daad upstream.
Having a paravirt indirect call in the IBRS restore path is not a good idea, since we are trying to protect from speculative execution of bogus indirect branch targets. It is also slower, so use native_wrmsrl() on the vmentry path too.
Signed-off-by: Paolo Bonzini pbonzini@redhat.com Reviewed-by: Jim Mattson jmattson@google.com Cc: David Woodhouse dwmw@amazon.co.uk Cc: KarimAllah Ahmed karahmed@amazon.de Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Radim Krčmář rkrcmar@redhat.com Cc: Thomas Gleixner tglx@linutronix.de Cc: kvm@vger.kernel.org Cc: stable@vger.kernel.org Fixes: d28b387fb74da95d69d2615732f50cceb38e9a4d Link: http://lkml.kernel.org/r/20180222154318.20361-2-pbonzini@redhat.com Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/svm.c | 7 ++++--- arch/x86/kvm/vmx.c | 7 ++++--- 2 files changed, 8 insertions(+), 6 deletions(-)
--- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -44,6 +44,7 @@ #include <asm/debugreg.h> #include <asm/kvm_para.h> #include <asm/irq_remapping.h> +#include <asm/microcode.h> #include <asm/nospec-branch.h>
#include <asm/virtext.h> @@ -4919,7 +4920,7 @@ static void svm_vcpu_run(struct kvm_vcpu * being speculatively taken. */ if (svm->spec_ctrl) - wrmsrl(MSR_IA32_SPEC_CTRL, svm->spec_ctrl); + native_wrmsrl(MSR_IA32_SPEC_CTRL, svm->spec_ctrl);
asm volatile ( "push %%" _ASM_BP "; \n\t" @@ -5029,10 +5030,10 @@ static void svm_vcpu_run(struct kvm_vcpu * save it. */ if (!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL)) - rdmsrl(MSR_IA32_SPEC_CTRL, svm->spec_ctrl); + svm->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL);
if (svm->spec_ctrl) - wrmsrl(MSR_IA32_SPEC_CTRL, 0); + native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
/* Eliminate branch target predictions from guest mode */ vmexit_fill_RSB(); --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -49,6 +49,7 @@ #include <asm/kexec.h> #include <asm/apic.h> #include <asm/irq_remapping.h> +#include <asm/microcode.h> #include <asm/nospec-branch.h>
#include "trace.h" @@ -8906,7 +8907,7 @@ static void __noclone vmx_vcpu_run(struc * being speculatively taken. */ if (vmx->spec_ctrl) - wrmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl); + native_wrmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl);
vmx->__launched = vmx->loaded_vmcs->launched; asm( @@ -9042,10 +9043,10 @@ static void __noclone vmx_vcpu_run(struc * save it. */ if (!msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL)) - rdmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl); + vmx->spec_ctrl = native_read_msr(MSR_IA32_SPEC_CTRL);
if (vmx->spec_ctrl) - wrmsrl(MSR_IA32_SPEC_CTRL, 0); + native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
/* Eliminate branch target predictions from guest mode */ vmexit_fill_RSB();
Patches currently in stable-queue which might be from pbonzini@redhat.com are
queue-4.9/kvm-x86-fix-smram-accessing-even-if-vm-is-shutdown.patch queue-4.9/kvm-x86-remove-indirect-msr-op-calls-from-spec_ctrl.patch queue-4.9/kvm-mmu-fix-overlap-between-public-and-private-memslots.patch queue-4.9/kvm-vmx-optimize-vmx_vcpu_run-and-svm_vcpu_run-by-marking-the-rdmsr-path-as-unlikely.patch