linux-kernel - Re: [PATCH 10/22] kvm: mmu: Add TDP MMU PF handler

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Message-ID: <4ee2a2cf-625b-3c10-a7da-75677ea37aa3@redhat.com>
Date:   Wed, 30 Sep 2020 18:55:18 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Cannon Matthews <cannonmatthews@...gle.com>,
        Peter Xu <peterx@...hat.com>, Peter Shier <pshier@...gle.com>,
        Peter Feiner <pfeiner@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>
Subject: Re: [PATCH 10/22] kvm: mmu: Add TDP MMU PF handler

On 30/09/20 18:37, Sean Christopherson wrote:
>> +
>> +	if (WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root_hpa)))
>> +		return RET_PF_RETRY;
> I feel like we should kill off these silly WARNs in the existing code instead
> of adding more.  If they actually fired, I'm pretty sure that they would
> continue firing and spamming the kernel log until the VM is killed as I don't
> see how restarting the guest will magically fix anything.

This is true, but I think it's better to be defensive.  They're
certainly all candidates for KVM_BUG_ON.

Paolo