From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46962) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fT0gN-0002BU-PJ for qemu-devel@nongnu.org; Wed, 13 Jun 2018 03:59:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fT0gK-0001f6-Ms for qemu-devel@nongnu.org; Wed, 13 Jun 2018 03:59:07 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:37462 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fT0gK-0001ek-Hm for qemu-devel@nongnu.org; Wed, 13 Jun 2018 03:59:04 -0400 From: Markus Armbruster References: <20180524044454.11792-1-peterx@redhat.com> <20180524044454.11792-2-peterx@redhat.com> <20180530074400-mutt-send-email-mst@kernel.org> <20180530063955.GA27442@xz-mi> <20180530155347.167708cc.cohuck@redhat.com> Date: Wed, 13 Jun 2018 09:59:02 +0200 In-Reply-To: <20180530155347.167708cc.cohuck@redhat.com> (Cornelia Huck's message of "Wed, 30 May 2018 15:53:47 +0200") Message-ID: <87wov3kth5.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v4 1/2] qemu-error: introduce {error|warn}_report_once List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: Peter Xu , "Michael S. Tsirkin" , Markus Armbruster , Jason Wang , qemu-devel@nongnu.org, Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Halil Pasic Cornelia Huck writes: > On Wed, 30 May 2018 14:39:55 +0800 > Peter Xu wrote: > >> On Wed, May 30, 2018 at 07:47:32AM +0300, Michael S. Tsirkin wrote: >> > On Thu, May 24, 2018 at 12:44:53PM +0800, Peter Xu wrote: >> > > There are many error_report()s that can be used in frequently called >> > > functions, especially on IO paths. That can be unideal in that >> > > malicious guest can try to trigger the error tons of time which might >> > > use up the log space on the host (e.g., libvirt can capture the stderr >> > > of QEMU and put it persistently onto disk). >> > >> > I think the problem is real enough but I think the API >> > isn't great as it stresses the mechanism. Which fundamentally does >> > not matter - we can print once or 10 times, or whatever. >> > >> > What happens here is a guest bug as opposed to hypervisor >> > bug. So I think a better name would be guest_error. >> >> For me error_report_once() is okay since after all it's only a way to >> dump something for the hypervisor management software (or the person >> who manages the QEMU instance), and I don't have a strong opinion to >> introduce a new guest_error() API. > > If we go with that suggestion, guest_{error,warn} should also prefix > the message with "Guest:" or so. Otherwise, it does not offer that much > more benefit. > > [And I think it should be a wrapper around the report_once > infrastructure.] I agree. Keep error_report_once() as low-level function (okay to stress mechanism there), then wrap whatever higher level functions we find useful around them, in followup patches. [...]