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

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Message-ID: <80f7f3dc-285f-39c3-655e-fd4a499f81a1@rbox.co>
Date:   Mon, 5 Jun 2023 22:42:59 +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 6/5/23 17:19, Sean Christopherson wrote:
> On Mon, Jun 05, 2023, Michal Luczaj wrote:
>> 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?
> 
> I doubt it, I'm guessing most cases are due to the author being overzealous for
> one reason or another, e.g. I suspect the test_bit() ones are due to the original
> author incorrectly assuming test_bit() returned an unsigned long, i.e. the bit,
> as opposed to the bool.
> 
> If you want to clean these up, I'd say "fix" the test_bit() cases, but leave the
> others alone.  The test_bit() ones are clearly redundant, and IMO can be actively
> due to implying test_bit() returns something other than a bool.

Done: https://lore.kernel.org/kvm/20230605200158.118109-1-mhal@rbox.co/