nested_vmx_setup_ctls_msrs() initializes the vmcs_conf.nested,
which stores the global VMX MSR configurations when nested is
supported, regardless of any particular CPUID settings for one
VM.
Commit 6defc591846d ("KVM: nVMX: include conditional controls
in /dev/kvm KVM_GET_MSRS") added the some feature flags for
secondary proc-based controls, so that those features can be
available in KVM_GET_MSRS. Yet this commit did not remove the
obsolete comments in nested_vmx_setup_ctls_msrs().
Just fix the comments, and no functional change intended.
Fixes: 6defc591846d ("KVM: nVMX: include conditional controls in /dev/kvm KVM_GET_MSRS")
Reported-by: Sean Christopherson <[email protected]>
Signed-off-by: Yu Zhang <[email protected]>
---
arch/x86/kvm/vmx/nested.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index b6f4411b613e..76cca5d5aa6b 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6854,11 +6854,7 @@ void nested_vmx_setup_ctls_msrs(struct vmcs_config *vmcs_conf, u32 ept_caps)
msrs->procbased_ctls_low &=
~(CPU_BASED_CR3_LOAD_EXITING | CPU_BASED_CR3_STORE_EXITING);
- /*
- * secondary cpu-based controls. Do not include those that
- * depend on CPUID bits, they are added later by
- * vmx_vcpu_after_set_cpuid.
- */
+ /* secondary cpu-based controls */
msrs->secondary_ctls_low = 0;
msrs->secondary_ctls_high = vmcs_conf->cpu_based_2nd_exec_ctrl;
--
2.17.1
On Thu, Dec 15, 2022, Yu Zhang wrote:
> nested_vmx_setup_ctls_msrs() initializes the vmcs_conf.nested,
> which stores the global VMX MSR configurations when nested is
> supported, regardless of any particular CPUID settings for one
> VM.
>
> Commit 6defc591846d ("KVM: nVMX: include conditional controls
> in /dev/kvm KVM_GET_MSRS") added the some feature flags for
> secondary proc-based controls, so that those features can be
> available in KVM_GET_MSRS. Yet this commit did not remove the
> obsolete comments in nested_vmx_setup_ctls_msrs().
>
> Just fix the comments, and no functional change intended.
>
> Fixes: 6defc591846d ("KVM: nVMX: include conditional controls in /dev/kvm KVM_GET_MSRS")
> Reported-by: Sean Christopherson <[email protected]>
I appreciate the nod, but you found this, not me :-)
> Signed-off-by: Yu Zhang <[email protected]>
> ---
> arch/x86/kvm/vmx/nested.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index b6f4411b613e..76cca5d5aa6b 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -6854,11 +6854,7 @@ void nested_vmx_setup_ctls_msrs(struct vmcs_config *vmcs_conf, u32 ept_caps)
> msrs->procbased_ctls_low &=
> ~(CPU_BASED_CR3_LOAD_EXITING | CPU_BASED_CR3_STORE_EXITING);
>
> - /*
> - * secondary cpu-based controls. Do not include those that
> - * depend on CPUID bits, they are added later by
> - * vmx_vcpu_after_set_cpuid.
> - */
> + /* secondary cpu-based controls */
Eh, just drop the comment. Pretty obvious this is for secondary execution controls.
> msrs->secondary_ctls_low = 0;
>
> msrs->secondary_ctls_high = vmcs_conf->cpu_based_2nd_exec_ctrl;
> --
> 2.17.1
>
>
> Eh, just drop the comment. Pretty obvious this is for secondary execution controls.
Thanks Sean. Well, I agree it is obvious.
This line was kept because there are comments for other groups of
control fields(e.g., exit/entry/pin-based/cpu-based controls etc.)
in nested_vmx_setup_ctls_msrs(). If we do not keep the one for secondary
cpu-based controls, we may just delete other comments as well. But
is that really necessary?
B.R.
Yu
On Fri, Dec 16, 2022, Yu Zhang wrote:
> >
> > Eh, just drop the comment. Pretty obvious this is for secondary execution controls.
> Thanks Sean. Well, I agree it is obvious.
>
> This line was kept because there are comments for other groups of
> control fields(e.g., exit/entry/pin-based/cpu-based controls etc.)
> in nested_vmx_setup_ctls_msrs(). If we do not keep the one for secondary
> cpu-based controls, we may just delete other comments as well. But
> is that really necessary?
Adding a patch to delete the various one-line comments is probably unnecessary
churn. The comments are kinda sorta helpful, but only because the function is a
giant and thus a bit hard to follow. A better solution than comments would be to
add helpers for each collection ("secondary_ctls" is a bit of a lie because it
handle VPID, EPT, VMFUNC, etc..., but whatever), e.g.
nested_vmx_setup_pinbased_ctls(msrs);
nested_vmx_setup_exit_ctls(msrs);
nested_vmx_setup_entry_ctls(msrs);
nested_vmx_setup_cpubased_ctls(msrs);
nested_vmx_setup_secondary_ctls(msrs);
nested_vmx_setup_misc_data(msrs);
On Fri, Dec 16, 2022 at 04:49:55PM +0000, Sean Christopherson wrote:
> On Fri, Dec 16, 2022, Yu Zhang wrote:
> > >
> > > Eh, just drop the comment. Pretty obvious this is for secondary execution controls.
> > Thanks Sean. Well, I agree it is obvious.
> >
> > This line was kept because there are comments for other groups of
> > control fields(e.g., exit/entry/pin-based/cpu-based controls etc.)
> > in nested_vmx_setup_ctls_msrs(). If we do not keep the one for secondary
> > cpu-based controls, we may just delete other comments as well. But
> > is that really necessary?
>
> Adding a patch to delete the various one-line comments is probably unnecessary
> churn. The comments are kinda sorta helpful, but only because the function is a
> giant and thus a bit hard to follow. A better solution than comments would be to
> add helpers for each collection ("secondary_ctls" is a bit of a lie because it
> handle VPID, EPT, VMFUNC, etc..., but whatever), e.g.
Good point. The "secondary_ctls" may be inaccurate, but I do not
have a better name in mind either...
>
> nested_vmx_setup_pinbased_ctls(msrs);
> nested_vmx_setup_exit_ctls(msrs);
> nested_vmx_setup_entry_ctls(msrs);
> nested_vmx_setup_cpubased_ctls(msrs);
> nested_vmx_setup_secondary_ctls(msrs);
Adding nested_vmx_setup_secondary_ctls() will impact
1> your previous patch to expose ENABLE_USR_WAIT_PAUSE control
https://lore.kernel.org/lkml/[email protected]/
2> my previous patch to simplify the setting of secondary proc-
based control:
https://www.spinics.net/lists/kernel/msg4582141.html
How about we combine our previous patches and the new ones together
in next version?
One more questionable comment for nested_vmx_setup_ctls_msrs() is:
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index b6f4411b613e..58b491f13ed7 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6744,8 +6744,6 @@ static u64 nested_vmx_calc_vmcs_enum_msr(void)
/*
* nested_vmx_setup_ctls_msrs() sets up variables containing the values to be
* returned for the various VMX controls MSRs when nested VMX is enabled.
- * The same values should also be used to verify that vmcs12 control fields are
- * valid during nested entry from L1 to L2.
* Each of these control msrs has a low and high 32-bit half: A low bit is on
* if the corresponding bit in the (32-bit) control field *must* be on, and a
* bit in the high half is on if the corresponding bit in the control field
> nested_vmx_setup_misc_data(msrs);
As to the misc data msr, do we really need a seperate function for it?
If yes, then what about the vmx basic msr, the ones for fixed bits in
CR0/4?
B.R.
Yu