linux-kernel - Re: [PATCH 1/2] KVM: VMX: Sanitize VM-Entry/VM-Exit control pairs at kvm

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Date:   Thu, 26 May 2022 09:04:26 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chenyi Qiang <chenyi.qiang@...el.com>,
        Lei Wang <lei4.wang@...el.com>
Subject: Re: [PATCH 1/2] KVM: VMX: Sanitize VM-Entry/VM-Exit control pairs at
 kvm_intel load time

On Thu, May 26, 2022 at 12:42:31AM +0000, Sean Christopherson wrote:
> On Thu, May 26, 2022, Yuan Yao wrote:
> > On Wed, May 25, 2022 at 09:04:46PM +0000, Sean Christopherson wrote:
> > > @@ -2614,6 +2635,20 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> > >  				&_vmentry_control) < 0)
> > >  		return -EIO;
> > >
> > > +	for (i = 0; i < ARRAY_SIZE(vmcs_entry_exit_pairs); i++) {
> > > +		u32 n_ctrl = vmcs_entry_exit_pairs[i].entry_control;
> > > +		u32 x_ctrl = vmcs_entry_exit_pairs[i].exit_control;
> > > +
> > > +		if (!(_vmentry_control & n_ctrl) == !(_vmexit_control & x_ctrl))
> > > +			continue;
> > > +
> > > +		pr_warn_once("Inconsistent VM-Entry/VM-Exit pair, entry = %x, exit = %x\n",
> > > +			     _vmentry_control & n_ctrl, _vmexit_control & x_ctrl);
> >
> > How about "n_ctrl, x_ctrl);" ? In 0/1 or 1/0 case this
> > outputs all information of real inconsistent bits but not 0.
>
> I thought about adding the stringified control name to the output (yay macros),
> but opted for the simplest approach because this should be a very, very rare
> event.  All the necessary info is there, it just takes a bit of leg work to get
> from a single control bit to the related control name and finally to its pair.
>
> I'm not totally against printing more info, but if we're going to bother doing so,
> my vote is to print names instead of numbers.

Agree for simplest approach because this should be rare event, thanks.