Re: [PATCH v3 03/27] KVM: VMX: Add support for the secondary VM exit controls

[Xin Li <xin@xxxxxxxxx>]

On 10/21/2024 1:28 AM, Chao Gao wrote:
> > +	for (i = 0; i < ARRAY_SIZE(vmcs_entry_exit_triplets); i++) {
> > +		u32 n_ctrl = vmcs_entry_exit_triplets[i].entry_control;
> > +		u32 x_ctrl = vmcs_entry_exit_triplets[i].exit_control;
> > +		u64 x_ctrl_2 = vmcs_entry_exit_triplets[i].exit_2nd_control;
> > +		bool has_n = n_ctrl && ((_vmentry_control & n_ctrl) == n_ctrl);
> > +		bool has_x = x_ctrl && ((_vmexit_control & x_ctrl) == x_ctrl);
> > +		bool has_x_2 = x_ctrl_2 && ((_secondary_vmexit_control & x_ctrl_2) == x_ctrl_2);
> > +
> > +		if (x_ctrl_2) {
> > +			/* Only activate secondary VM exit control bit should be set */
> > +			if ((_vmexit_control & x_ctrl) == VM_EXIT_ACTIVATE_SECONDARY_CONTROLS) {
> > +				if (has_n == has_x_2)
> > +					continue;
> > +			} else {
> > +				/* The feature should not be supported in any control */
> > +				if (!has_n && !has_x && !has_x_2)
> > +					continue;
> > +			}
> > +		} else if (has_n == has_x) {
> > 			continue;
> > +		}
> >
> > -		pr_warn_once("Inconsistent VM-Entry/VM-Exit pair, entry = %x, exit = %x\n",
> > -			     _vmentry_control & n_ctrl, _vmexit_control & x_ctrl);
> > +		pr_warn_once("Inconsistent VM-Entry/VM-Exit triplet, entry = %x, exit = %x, secondary_exit = %llx\n",
> > +			     _vmentry_control & n_ctrl, _vmexit_control & x_ctrl,
> > +			     _secondary_vmexit_control & x_ctrl_2);
> >
> > 		if (error_on_inconsistent_vmcs_config)
> > 			return -EIO;
> >
> > 		_vmentry_control &= ~n_ctrl;
> > 		_vmexit_control &= ~x_ctrl;
>
> w/ patch 4, VM_EXIT_ACTIVATE_SECONDARY_CONTROLS is cleared if FRED fails in the
> consistent check. this means, all features in the secondary vm-exit controls
> are removed. it is overkill.

Good catch!

> I prefer to maintain a separate table for the secondary VM-exit controls:
>
>   	struct {
>   		u32 entry_control;
>   		u64 exit2_control;
> 	} const vmcs_entry_exit2_pairs[] = {
> 		{ VM_ENTRY_LOAD_IA32_FRED, SECONDARY_VM_EXIT_SAVE_IA32_FRED |
> 					   SECONDARY_VM_EXIT_LOAD_IA32_FRED},
> 	};
>
> 	for (i = 0; i < ARRAY_SIZE(vmcs_entry_exit2_pairs); i++) {
> 	...
> 	}

Hmm, I prefer one table, as it's more straight forward.

> > +		_secondary_vmexit_control &= ~x_ctrl_2;
> > 	}
> >
> > 	rdmsrl(MSR_IA32_VMX_BASIC, basic_msr);