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Wed, 21 Apr 2021 09:23:14 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id DD9A4B2D5; Wed, 21 Apr 2021 09:23:13 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 10f6d7e8-ef6b-4423-ba49-429761ac6365 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1618996994; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=J9hzIB0ECvpA9dn/t63pp56N2ttbwTbJRvNY1u3nCfQ=; b=GUAFFxMuRwOlpXmdZyeXS209o0CAesfPXtfPa6RfDxfShjRzht+3SDeB0KOrr1FilSgOVT Q5nu4A+P41cKd0GmgwquCyzSK2MHzSxAcTFkOvjhrmrpIlrpJI9XefnG7PjE8mu80LNxX+ 10/5WrvLWSoC5bLzhT8uqDz4+fs3+MQ= Subject: Re: [PATCH v2] VT-d: Don't assume register-based invalidation is always supported To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Chao Gao Cc: xen-devel@lists.xenproject.org, Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini , Wei Liu , Kevin Tian References: <20200401200606.48752-1-chao.gao@intel.com> <3afbdba8-b25c-985c-6c5f-20077cb37d3f@suse.com> From: Jan Beulich Message-ID: <9276b757-a340-b0f3-3427-13b7bc5dcb9e@suse.com> Date: Wed, 21 Apr 2021 11:23:13 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 20.04.2021 18:17, Roger Pau Monné wrote: > On Tue, Apr 20, 2021 at 05:38:51PM +0200, Jan Beulich wrote: >> On 20.04.2021 17:08, Roger Pau Monné wrote: >>> On Thu, Apr 02, 2020 at 04:06:06AM +0800, Chao Gao wrote: >>>> --- a/xen/drivers/passthrough/vtd/qinval.c >>>> +++ b/xen/drivers/passthrough/vtd/qinval.c >>>> @@ -442,6 +442,23 @@ int enable_qinval(struct vtd_iommu *iommu) >>>> return 0; >>>> } >>>> >>>> +static int vtd_flush_context_noop(struct vtd_iommu *iommu, uint16_t did, >>>> + uint16_t source_id, uint8_t function_mask, >>>> + uint64_t type, bool flush_non_present_entry) >>>> +{ >>>> + dprintk(XENLOG_ERR VTDPREFIX, "IOMMU: Cannot flush CONTEXT.\n"); >>>> + return -EIO; >>>> +} >>>> + >>>> +static int vtd_flush_iotlb_noop(struct vtd_iommu *iommu, uint16_t did, >>>> + uint64_t addr, unsigned int size_order, >>>> + uint64_t type, bool flush_non_present_entry, >>>> + bool flush_dev_iotlb) >>>> +{ >>>> + dprintk(XENLOG_ERR VTDPREFIX, "IOMMU: Cannot flush IOTLB.\n"); >>>> + return -EIO; >>>> +} >>> >>> I think I would add an ASSERT_UNREACHABLE() to both noop handlers >>> above, as I would expect trying to use them without the proper mode >>> being configured would point to an error elsewhere? >> >> If such an assertion triggered e.g. during S3 suspend/resume, it may >> lead to the box simply not doing anything useful, without there being >> any way to know what went wrong. If instead the system at least >> managed to resume, the log message could be observed. > > Oh, OK then. I'm simply worried that people might ignore such one line > messages, maybe add a WARN? Hmm, yes, perhaps - would allow seeing right away where the call came from. Chao, I'd again be fine to flip the dprintk()-s to WARN()-s while committing. But of course only provided you and Kevin (as the maintainer) agree. > Would it make sense to mark as tainted which could help identify the > issue on production builds? Maybe that's too much. Yeah, for something we expect shouldn't ever happen ... Jan