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Tue, 18 May 2021 15:13:24 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C69FCADAA; Tue, 18 May 2021 15:13:23 +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: bb3f3790-f0a2-4af4-87de-3164b64ab22b 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=1621350803; 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=nzFvHABDtDjkJraAdgukYDaFZGMeiKGGlNuVgZ5vXjQ=; b=PZTg05gsZF4j+7eQ+uXdhXFGFGnlHjtz5z/Kxz320SSZMTRnsb90Ht+QRj6hcyh5L6AA1v mQBNFlNrJXD+TvypwD5Ce+dpJrn+L7eLJzCbBC8/AMVXG6gewnfhxbcvj7+7Cmy1MzC/Em 8aOvewi6UmaEcN4g5DrtMsQHMxGo5RM= Subject: Re: [PATCH v3 2/5] xen/common: Guard iommu symbols with CONFIG_HAS_PASSTHROUGH To: Julien Grall , Connor Davis Cc: Bobby Eshleman , Alistair Francis , Andrew Cooper , George Dunlap , Ian Jackson , Stefano Stabellini , Wei Liu , Paul Durrant , xen-devel@lists.xenproject.org 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> <8e415cac-a8b3-67a6-2f7b-489b964ceb50@suse.com> From: Jan Beulich Message-ID: <922c6304-9299-a697-2405-1b7f6d069842@suse.com> Date: Tue, 18 May 2021 17:13:22 +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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 18.05.2021 16:06, Julien Grall wrote: > > > On 18/05/2021 07:27, Jan Beulich wrote: >> 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. > > I would like to avoid adding more #ifdef CONFIG_X86 in the common code. > Can we instead provide a wrapper for them? Doable, sure, but I don't know whether Connor is up to going this more extensive route. Jan