linux-kernel - Re: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver lowest-priority interrupts

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Message-ID: <56A649FA.7010209@redhat.com>
Date:	Mon, 25 Jan 2016 17:14:50 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Radim Krcmár <rkrcmar@...hat.com>
Cc:	"Wu, Feng" <feng.wu@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] KVM: x86: Use vector-hashing to deliver
 lowest-priority interrupts



On 25/01/2016 16:20, Radim Krcmár wrote:
> 2016-01-25 13:25+0100, Paolo Bonzini:
>> On 22/01/2016 15:01, Radim Krcmár wrote:
>>>>         for (i = 0; i <= mod; i++) {
>>>>                 idx = find_next_bit(bitmap, bitmap_size, idx + 1);
>>>>                 BUG_ON(idx == bitmap_size);
>>>>         }
>>
>> WARN_ON, not BUG_ON.
> 
> Callers don't check the return value for an error, because every error
> is a BUG now.  I think that we should check if we return bitmap_size.
> (Current paths could dereference NULL or throw unrelated warnings.)

You can probably just return a random number (e.g. zero or
find_first_bit) if the bug is hit.  But really, the bug is easy enough
to verify that BUG_ON might even be okay...

Paolo