* [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF
@ 2019-08-26 19:30 Waiman Long
2019-09-26 17:29 ` Waiman Long
2019-09-27 16:02 ` Paolo Bonzini
0 siblings, 2 replies; 5+ messages in thread
From: Waiman Long @ 2019-08-26 19:30 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov
Cc: x86, kvm, linux-kernel, Waiman Long
The l1tf_vmx_mitigation is only set to VMENTER_L1D_FLUSH_NOT_REQUIRED
when the ARCH_CAPABILITIES MSR indicates that L1D flush is not required.
However, if the CPU is not affected by L1TF, l1tf_vmx_mitigation will
still be set to VMENTER_L1D_FLUSH_AUTO. This is certainly not the best
option for a !X86_BUG_L1TF CPU.
So force l1tf_vmx_mitigation to VMENTER_L1D_FLUSH_NOT_REQUIRED to make it
more explicit in case users are checking the vmentry_l1d_flush parameter.
Signed-off-by: Waiman Long <longman@redhat.com>
---
arch/x86/kvm/vmx/vmx.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 42ed3faa6af8..a00ce3d6bbfd 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7896,6 +7896,8 @@ static int __init vmx_init(void)
vmx_exit();
return r;
}
+ } else {
+ l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
}
#ifdef CONFIG_KEXEC_CORE
--
2.18.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF
2019-08-26 19:30 [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF Waiman Long
@ 2019-09-26 17:29 ` Waiman Long
2019-09-27 15:55 ` Borislav Petkov
2019-09-27 16:02 ` Paolo Bonzini
1 sibling, 1 reply; 5+ messages in thread
From: Waiman Long @ 2019-09-26 17:29 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov
Cc: x86, kvm, linux-kernel
On 8/26/19 3:30 PM, Waiman Long wrote:
> The l1tf_vmx_mitigation is only set to VMENTER_L1D_FLUSH_NOT_REQUIRED
> when the ARCH_CAPABILITIES MSR indicates that L1D flush is not required.
> However, if the CPU is not affected by L1TF, l1tf_vmx_mitigation will
> still be set to VMENTER_L1D_FLUSH_AUTO. This is certainly not the best
> option for a !X86_BUG_L1TF CPU.
>
> So force l1tf_vmx_mitigation to VMENTER_L1D_FLUSH_NOT_REQUIRED to make it
> more explicit in case users are checking the vmentry_l1d_flush parameter.
>
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 42ed3faa6af8..a00ce3d6bbfd 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7896,6 +7896,8 @@ static int __init vmx_init(void)
> vmx_exit();
> return r;
> }
> + } else {
> + l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
> }
>
> #ifdef CONFIG_KEXEC_CORE
Ping. Any comment on that one?
Cheers,
Longman
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF
2019-09-26 17:29 ` Waiman Long
@ 2019-09-27 15:55 ` Borislav Petkov
2019-09-27 16:04 ` Paolo Bonzini
0 siblings, 1 reply; 5+ messages in thread
From: Borislav Petkov @ 2019-09-27 15:55 UTC (permalink / raw)
To: Waiman Long
Cc: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, x86, kvm, linux-kernel
On Thu, Sep 26, 2019 at 01:29:28PM -0400, Waiman Long wrote:
> On 8/26/19 3:30 PM, Waiman Long wrote:
> > The l1tf_vmx_mitigation is only set to VMENTER_L1D_FLUSH_NOT_REQUIRED
> > when the ARCH_CAPABILITIES MSR indicates that L1D flush is not required.
> > However, if the CPU is not affected by L1TF, l1tf_vmx_mitigation will
> > still be set to VMENTER_L1D_FLUSH_AUTO. This is certainly not the best
> > option for a !X86_BUG_L1TF CPU.
> >
> > So force l1tf_vmx_mitigation to VMENTER_L1D_FLUSH_NOT_REQUIRED to make it
> > more explicit in case users are checking the vmentry_l1d_flush parameter.
> >
> > Signed-off-by: Waiman Long <longman@redhat.com>
> > ---
> > arch/x86/kvm/vmx/vmx.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 42ed3faa6af8..a00ce3d6bbfd 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -7896,6 +7896,8 @@ static int __init vmx_init(void)
> > vmx_exit();
> > return r;
> > }
> > + } else {
> > + l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
> > }
> >
> > #ifdef CONFIG_KEXEC_CORE
>
> Ping. Any comment on that one?
I'd move that logic with the if (boot_cpu_has(X86_BUG_L1TF)) check inside
vmx_setup_l1d_flush() so that I have this:
if (!boot_cpu_has_bug(X86_BUG_L1TF)) {
l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
return 0;
}
if (!enable_ept) {
...
}
inside the function and outside am left with:
r = vmx_setup_l1d_flush(vmentry_l1d_flush_param);
if (r) {
vmx_exit();
return r;
}
only. This way I'm concentrating the whole l1tf_vmx_mitigation picking
apart in one place.
Also, note that X86_BUG flags are checked with boot_cpu_has_bug() even
if it boils down to the same thing now.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF
2019-08-26 19:30 [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF Waiman Long
2019-09-26 17:29 ` Waiman Long
@ 2019-09-27 16:02 ` Paolo Bonzini
1 sibling, 0 replies; 5+ messages in thread
From: Paolo Bonzini @ 2019-09-27 16:02 UTC (permalink / raw)
To: Waiman Long, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov
Cc: x86, kvm, linux-kernel
On 26/08/19 21:30, Waiman Long wrote:
> The l1tf_vmx_mitigation is only set to VMENTER_L1D_FLUSH_NOT_REQUIRED
> when the ARCH_CAPABILITIES MSR indicates that L1D flush is not required.
> However, if the CPU is not affected by L1TF, l1tf_vmx_mitigation will
> still be set to VMENTER_L1D_FLUSH_AUTO. This is certainly not the best
> option for a !X86_BUG_L1TF CPU.
>
> So force l1tf_vmx_mitigation to VMENTER_L1D_FLUSH_NOT_REQUIRED to make it
> more explicit in case users are checking the vmentry_l1d_flush parameter.
>
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 42ed3faa6af8..a00ce3d6bbfd 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7896,6 +7896,8 @@ static int __init vmx_init(void)
> vmx_exit();
> return r;
> }
> + } else {
> + l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
> }
>
> #ifdef CONFIG_KEXEC_CORE
>
Queued (for -rc2), thanks.
Paolo
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF
2019-09-27 15:55 ` Borislav Petkov
@ 2019-09-27 16:04 ` Paolo Bonzini
0 siblings, 0 replies; 5+ messages in thread
From: Paolo Bonzini @ 2019-09-27 16:04 UTC (permalink / raw)
To: Borislav Petkov, Waiman Long
Cc: Radim Krčmář,
Thomas Gleixner, Ingo Molnar, x86, kvm, linux-kernel
On 27/09/19 17:55, Borislav Petkov wrote:
> I'd move that logic with the if (boot_cpu_has(X86_BUG_L1TF)) check inside
> vmx_setup_l1d_flush() so that I have this:
>
> if (!boot_cpu_has_bug(X86_BUG_L1TF)) {
> l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
> return 0;
> }
>
> if (!enable_ept) {
> ...
>
> }
>
> inside the function and outside am left with:
>
> r = vmx_setup_l1d_flush(vmentry_l1d_flush_param);
> if (r) {
> vmx_exit();
> return r;
> }
>
> only. This way I'm concentrating the whole l1tf_vmx_mitigation picking
> apart in one place.
Right you are, I'm sending v2.
Paolo
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-09-27 16:04 UTC | newest]
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2019-08-26 19:30 [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF Waiman Long
2019-09-26 17:29 ` Waiman Long
2019-09-27 15:55 ` Borislav Petkov
2019-09-27 16:04 ` Paolo Bonzini
2019-09-27 16:02 ` Paolo Bonzini
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