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

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Date:   Mon, 5 Jun 2023 13:53:13 +0200
From:   Michal Luczaj <mhal@...x.co>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     dmatlack@...gle.com, mizhang@...gle.com, isaku.yamahata@...il.com,
        pbonzini@...hat.com, Wei Wang <wei.w.wang@...el.com>,
        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 18:56, Sean Christopherson wrote:
> On Fri, Jun 02, 2023, Michal Luczaj wrote:
>> 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)...
> 
> Ya, I saw that, which in addition to Wei's ping, is what reminded me that the
> KVM_BUG_ON() fix hadn't been merged.
> 
>> Is it worth a patch (perhaps along with chopping off !! in
>> kvm_msr_allowed() and few other places)?
> 
> Yes, I think so.

OK, so xa_store() aside[*], I see some bool-to-bools:

arch/x86/kvm/x86.c:
	kvm_msr_allowed():allowed = !!test_bit(index - start, bitmap);
arch/x86/kvm/hyperv.c:
	kvm_hv_hypercall():hc.rep = !!(hc.rep_cnt || hc.rep_idx);
arch/x86/kvm/mmu/mmu.c:
	update_pkru_bitmask():
		pkey_bits = !!check_pkey;
		pkey_bits |= (!!check_write) << 1;
arch/x86/kvm/svm/svm.c:
	msr_write_intercepted():return !!test_bit(bit_write,  &tmp);
	svm_vcpu_after_set_cpuid():
		2x set_msr_interception...
tools/testing/selftests/kvm/x86_64/vmx_exception_with_invalid_guest_state.c:
	set_or_clear_invalid_guest_state():sregs.tr.unusable = !!set;

But perhaps this is a matter of style and those were meant to be this kind-of
explicit?

[*] https://lore.kernel.org/kvm/20230605114852.288964-1-mhal@rbox.co/