linux-kernel - Re: [PATCH v2 8/8] KVM: x86: Fold decache_cr3() into cache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87y2y53itd.fsf@vitty.brq.redhat.com>
Date:   Mon, 30 Sep 2019 17:27:58 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Reto Buerki <reet@...elabs.ch>,
        Liran Alon <liran.alon@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH v2 8/8] KVM: x86: Fold decache_cr3() into cache_reg()

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> On Mon, Sep 30, 2019 at 12:58:53PM +0200, Vitaly Kuznetsov wrote:
>> Sean Christopherson <sean.j.christopherson@...el.com> writes:
>> 
>> > Handle caching CR3 (from VMX's VMCS) into struct kvm_vcpu via the common
>> > cache_reg() callback and drop the dedicated decache_cr3().  The name
>> > decache_cr3() is somewhat confusing as the caching behavior of CR3
>> > follows that of GPRs, RFLAGS and PDPTRs, (handled via cache_reg()), and
>> > has nothing in common with the caching behavior of CR0/CR4 (whose
>> > decache_cr{0,4}_guest_bits() likely provided the 'decache' verbiage).
>> >
>> > Note, this effectively adds a BUG() if KVM attempts to cache CR3 on SVM.
>> > Opportunistically add a WARN_ON_ONCE() in VMX to provide an equivalent
>> > check.
>> 
>> Just to justify my idea of replacing such occasions with
>> KVM_INTERNAL_ERROR by setting a special 'kill ASAP' bit somewhere:
>> 
>> This WARN_ON_ONCE() falls in the same category (IMO).
>
> Maybe something like KVM_BUG_ON?  E.g.:
>
> #define KVM_BUG_ON(kvm, cond)		\
> ({					\
> 	int r;				\
> 					\
> 	if (r = WARN_ON_ONCE(cond))	\
> 		kvm->vm_bugged = true;	\
> 	r;				\
> )}
> 	

Yes, that's more or less what I meant! (to me 'vm_bugged' sounds like
there was a bug in the VM but the bug is actually in KVM so maybe
something like 'kvm_internal_bug' to make it explicit?)

-- 
Vitaly