linux-kernel - Re: [PATCH v7 053/102] KVM: TDX: don't request KVM_REQ_APIC_PAGE

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Message-ID: <20220712061439.GA28707@gao-cwp>
Date:   Tue, 12 Jul 2022 14:14:45 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     Yuan Yao <yuan.yao@...ux.intel.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v7 053/102] KVM: TDX: don't request
 KVM_REQ_APIC_PAGE_RELOAD

On Tue, Jul 12, 2022 at 11:47:43AM +0800, Yuan Yao wrote:
>On Mon, Jun 27, 2022 at 02:53:45PM -0700, isaku.yamahata@...el.com wrote:
>> From: Isaku Yamahata <isaku.yamahata@...el.com>
>>
>> TDX doesn't need APIC page depending on vapic and its callback is
>> WARN_ON_ONCE(is_tdx).  To avoid unnecessary overhead and WARN_ON_ONCE(),
>> skip requesting KVM_REQ_APIC_PAGE_RELOAD when TD.

!kvm_gfn_shared_mask() doesn't ensure the VM is a TD. Right?

>>
>>
>> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
>> ---
>>  arch/x86/kvm/x86.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 8f57dfb2a8c9..c90ec611de2f 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -10042,7 +10042,8 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
>>  	 * Update it when it becomes invalid.
>>  	 */
>>  	apic_address = gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
>> -	if (start <= apic_address && apic_address < end)
>> +	if (start <= apic_address && apic_address < end &&
>> +	    !kvm_gfn_shared_mask(kvm))
>
>Minor: please condier to check kvm_gfn_shared_mask(kvm) before range,
>means firstly check is or not, then suitable or not.
>
>>  		kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
>>  }
>>
>> --
>> 2.25.1
>>