linux-kernel - Re: [PATCH v4 19/32] KVM: x86: Explicitly track all possibilities for APIC map's logical modes

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Date:   Tue, 27 Dec 2022 12:30:18 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alejandro Jimenez <alejandro.j.jimenez@...cle.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Li RongQing <lirongqing@...du.com>
Subject: Re: [PATCH v4 19/32] KVM: x86: Explicitly track all possibilities for
 APIC map's logical modes

On 12/17/22 00:34, Sean Christopherson wrote:
> On Fri, Dec 16, 2022, Sean Christopherson wrote:
>> On Thu, Dec 08, 2022, Maxim Levitsky wrote:
> 
> ...
> 
>>>> @@ -282,7 +291,8 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
>>>>   		if (!apic_x2apic_mode(apic) && !new->phys_map[xapic_id])
>>>>   			new->phys_map[xapic_id] = apic;
>>>>   
>>>> -		if (!kvm_apic_sw_enabled(apic))
>>>> +		if (new->logical_mode == KVM_APIC_MODE_MAP_DISABLED ||
>>>> +		    !kvm_apic_sw_enabled(apic))
>>>>   			continue;
>>> Very minor nitpick: it feels to me that code that updates the logical mode of the
>>> map, might be better to be in a function, or in 'if', like
>>
>> An if-statement would be rough due to the indentation.  A function works well
>> though, especially if both the physical and logical chunks are put into helpers.
>> E.g. the patch at the bottom (with other fixup for this patch) yields:
>>
>> 	new->max_apic_id = max_id;
>> 	new->logical_mode = KVM_APIC_MODE_SW_DISABLED;
>>
>> 	kvm_for_each_vcpu(i, vcpu, kvm) {
>> 		if (!kvm_apic_present(vcpu))
>> 			continue;
>>
>> 		if (kvm_recalculate_phys_map(new, vcpu, &xapic_id_mismatch)) {
>> 			kvfree(new);
>> 			new = NULL;
>> 			goto out;
>> 		}
>>
>> 		kvm_recalculate_logical_map(new, vcpu);
>> 	}
>>
>> I'll tack that patch on at the end of the series if it looks ok.

Yes, please send as a follow up.

Paolo