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Tue, 18 May 2021 06:27:36 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3EDE9AF0B; Tue, 18 May 2021 06:27:35 +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: 0f343995-a874-42e9-8273-d1fa9b7f3c7f 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=1621319255; 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=vH3Fcfj+/jcnPVnbRR9qiOn/UQ1RAcuNx8X60zLDJa8=; b=aGFP+S0i8Exn4fzP/ywQEp4O5zEpIbrXDP953dzfidosYZMrL5n+Npx3ND3SVHiLua6/8X ravvah4gD/1Jds1eRoAMOmiCXHz8X+KJNjufSgeOv6vUuycsMcVJQOAzqVt3nMZ4bolr01 9Psvt6iBZhrcYtGklafxObPkHiXZCvE= Subject: Re: [PATCH v3 2/5] xen/common: Guard iommu symbols with CONFIG_HAS_PASSTHROUGH To: Connor Davis Cc: Bobby Eshleman , Alistair Francis , Andrew Cooper , George Dunlap , Ian Jackson , Stefano Stabellini , Wei Liu , Paul Durrant , xen-devel@lists.xenproject.org, Julien Grall References: <1156cb116da19ef64323e472bb6b6e87c6c73d77.1621017334.git.connojdavis@gmail.com> <556d1933-3b11-0780-edec-b6dc1729bc56@suse.com> <98b429d0-2673-624e-1690-9c0e8373ed5b@xen.org> <7cf966f6-7ccf-ba63-2b67-129577a7ca53@gmail.com> From: Jan Beulich Message-ID: <8e415cac-a8b3-67a6-2f7b-489b964ceb50@suse.com> Date: Tue, 18 May 2021 08:27:34 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <7cf966f6-7ccf-ba63-2b67-129577a7ca53@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 18.05.2021 06:11, Connor Davis wrote: > > On 5/17/21 9:42 AM, Julien Grall wrote: >> Hi Jan, >> >> On 17/05/2021 12:16, Jan Beulich wrote: >>> On 14.05.2021 20:53, Connor Davis wrote: >>>> --- a/xen/common/memory.c >>>> +++ b/xen/common/memory.c >>>> @@ -294,7 +294,9 @@ int guest_remove_page(struct domain *d, unsigned >>>> long gmfn) >>>>       p2m_type_t p2mt; >>>>   #endif >>>>       mfn_t mfn; >>>> +#ifdef CONFIG_HAS_PASSTHROUGH >>>>       bool *dont_flush_p, dont_flush; >>>> +#endif >>>>       int rc; >>>>     #ifdef CONFIG_X86 >>>> @@ -385,13 +387,17 @@ int guest_remove_page(struct domain *d, >>>> unsigned long gmfn) >>>>        * Since we're likely to free the page below, we need to suspend >>>>        * xenmem_add_to_physmap()'s suppressing of IOMMU TLB flushes. >>>>        */ >>>> +#ifdef CONFIG_HAS_PASSTHROUGH >>>>       dont_flush_p = &this_cpu(iommu_dont_flush_iotlb); >>>>       dont_flush = *dont_flush_p; >>>>       *dont_flush_p = false; >>>> +#endif >>>>         rc = guest_physmap_remove_page(d, _gfn(gmfn), mfn, 0); >>>>   +#ifdef CONFIG_HAS_PASSTHROUGH >>>>       *dont_flush_p = dont_flush; >>>> +#endif >>>>         /* >>>>        * With the lack of an IOMMU on some platforms, domains with >>>> DMA-capable >>>> @@ -839,11 +845,13 @@ int xenmem_add_to_physmap(struct domain *d, >>>> struct xen_add_to_physmap *xatp, >>>>       xatp->gpfn += start; >>>>       xatp->size -= start; >>>>   +#ifdef CONFIG_HAS_PASSTHROUGH >>>>       if ( is_iommu_enabled(d) ) >>>>       { >>>>          this_cpu(iommu_dont_flush_iotlb) = 1; >>>>          extra.ppage = &pages[0]; >>>>       } >>>> +#endif >>>>         while ( xatp->size > done ) >>>>       { >>>> @@ -868,6 +876,7 @@ int xenmem_add_to_physmap(struct domain *d, >>>> struct xen_add_to_physmap *xatp, >>>>           } >>>>       } >>>>   +#ifdef CONFIG_HAS_PASSTHROUGH >>>>       if ( is_iommu_enabled(d) ) >>>>       { >>>>           int ret; >>>> @@ -894,6 +903,7 @@ int xenmem_add_to_physmap(struct domain *d, >>>> struct xen_add_to_physmap *xatp, >>>>           if ( unlikely(ret) && rc >= 0 ) >>>>               rc = ret; >>>>       } >>>> +#endif >>>>         return rc; >>>>   } >>> >>> I wonder whether all of these wouldn't better become CONFIG_X86: >>> ISTR Julien indicating that he doesn't see the override getting used >>> on Arm. (Julien, please correct me if I'm misremembering.) >> >> Right, so far, I haven't been in favor to introduce it because: >>    1) The P2M code may free some memory. So you can't always ignore >> the flush (I think this is wrong for the upper layer to know when this >> can happen). >>    2) It is unclear what happen if the IOMMU TLBs and the PT contains >> different mappings (I received conflicted advice). >> >> So it is better to always flush and as early as possible. > > So keep it as is or switch to CONFIG_X86? Please switch, unless anyone else voices a strong opinion towards keeping as is. Jan