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From: Paolo Bonzini <pbonzini@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Vihas Mak <makvihas@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>
Cc: seanjc@google.com, wanpengli@tencent.com, jmattson@google.com,
	joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com,
	bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
	hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: fix cocci warnings
Date: Tue, 16 Nov 2021 10:50:32 +0100	[thread overview]
Message-ID: <04b7e240-8e1d-1402-3cef-e65469bd9317@redhat.com> (raw)
In-Reply-To: <87o86leo34.fsf@redhat.com>

On 11/15/21 10:59, Vitaly Kuznetsov wrote:
> One minor remark: 'kvm_set_pte_rmapp()' handler is passed to
> 'kvm_handle_gfn_range()' which does
> 
>          bool ret = false;
> 
>          for_each_slot_rmap_range(...)
>                  ret |= handler(...);
> 
> and I find '|=' to not be very natural with booleans. I'm not sure it's
> worth changing though.

Changing that would be "harder" than it seems because "ret = ret || 
handler(...)" is wrong, and "|" is even more unnatural than "|=" (so 
much that clang warns about it).

In fact I wonder if "|=" with a bool might end up warning with clang, 
which we should check before applying this patch.  It doesn't seem to be 
in the original commit[1], but better safe than sorry: Nick, does clang 
intend to warn also about "ret |= fn()" and "ret &= fn()"?  Technically, 
it is a bitwise operation with side-effects in the RHS.

Paolo

[1] https://github.com/llvm/llvm-project/commit/f59cc9542bfb461


  parent reply	other threads:[~2021-11-16  9:51 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-14 16:43 [PATCH] KVM: x86: fix cocci warnings Vihas Mak
2021-11-15  9:59 ` Vitaly Kuznetsov
2021-11-15 11:33   ` Vihas Mak
2021-11-16  9:50   ` Paolo Bonzini [this message]
2021-11-16 18:16     ` Nick Desaulniers
2021-11-15 11:43 ` Peter Zijlstra
2021-11-15 17:06   ` Paolo Bonzini
2021-11-15 20:49     ` Peter Zijlstra
2021-11-16  7:38       ` Paolo Bonzini

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