linux-kernel - Re: [PATCH v2] KVM: allow KVM_BUG/KVM_BUG

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Message-ID: <8f319a1e-a869-b666-b606-c0b4764ef7b1@rbox.co>
Date:   Fri, 2 Jun 2023 18:47:42 +0200
From:   Michal Luczaj <mhal@...x.co>
To:     Sean Christopherson <seanjc@...gle.com>, dmatlack@...gle.com,
        mizhang@...gle.com, isaku.yamahata@...il.com, pbonzini@...hat.com,
        Wei Wang <wei.w.wang@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: allow KVM_BUG/KVM_BUG_ON to handle 64-bit cond

On 6/2/23 03:20, Sean Christopherson wrote:
> On Tue, 07 Mar 2023 21:52:33 +0800, Wei Wang wrote:
>> Current KVM_BUG and KVM_BUG_ON assume that 'cond' passed from callers is
>> 32-bit as it casts 'cond' to the type of int. This will be wrong if 'cond'
>> provided by a caller is 64-bit, e.g. an error code of 0xc0000d0300000000
>> will be converted to 0, which is not expected.
>>
>> Improves the implementation by using bool in KVM_BUG and KVM_BUG_ON.
>> 'bool' is preferred to 'int' as __ret is essentially used as a boolean
>> and coding-stytle.rst documents that use of bool is encouraged to improve
>> readability and is often a better option than 'int' for storing boolean
>> values.
>>
>> [...]
> 
> Applied to kvm-x86 generic, thanks!
> 
> [1/1] KVM: allow KVM_BUG/KVM_BUG_ON to handle 64-bit cond
>       https://github.com/kvm-x86/linux/commit/c9d601548603

I guess this makes the !! in kvm_vm_ioctl_create_vcpu() unnecessary:

KVM_BUG_ON(!!xa_store(&kvm->vcpu_array, vcpu->vcpu_idx, vcpu, 0)...

Is it worth a patch (perhaps along with chopping off !! in
kvm_msr_allowed() and few other places)?