linux-kernel - Re: [PART1 RFC v2 07/10] svm: Add VMEXIT handlers for AVIC

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Date:	Tue, 8 Mar 2016 23:05:41 +0100
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	joro@...tes.org, bp@...en8.de, gleb@...nel.org,
	alex.williamson@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, wei@...hat.com,
	sherry.hurwitz@....com
Subject: Re: [PART1 RFC v2 07/10] svm: Add VMEXIT handlers for AVIC

2016-03-07 16:58+0100, Paolo Bonzini:
>> +	case AVIC_INCMP_IPI_ERR_INV_TARGET:
>> +		pr_err("%s: Invalid IPI target (icr=%#08x:%08x, idx=%u)\n",
>> +		       __func__, icrh, icrl, index);
>> +		BUG();
>> +		break;
>> +	case AVIC_INCMP_IPI_ERR_INV_BK_PAGE:
>> +		pr_err("%s: Invalid bk page (icr=%#08x:%08x, idx=%u)\n",
>> +		       __func__, icrh, icrl, index);
>> +		BUG();
>> +		break;
> 
> Please use WARN(1, "%s: Invalid bk page (icr=%#08x:%08x, idx=%u)\n",
> __func__, icrh, icrl, index) (and likewise for invalid target) instead
> of BUG().

I think that if we hit one of these, then WARNs would just flood the
log.  I'd prefer WARN_ONCE on AVIC_INCMP_IPI_ERR_INV_BK_PAGE.
(Btw. aren't icr and idx are pointless on this error?  and the function
 name should be printed by WARN.)

Invalid target is triggerable by the guest (by sending IPI to a
non-existent LAPIC), so warning log level seems too severe.
pr_info_ratelimited() or nothing would be better.