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Tue, 18 May 2021 14:06:32 +0000 Received: from [54.239.6.188] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1lj0Mi-0002FN-DI; Tue, 18 May 2021 14:06:32 +0000 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" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=fmCN197QOAwfYxZ0Bl55KFhJHHuAFHlw1wnxSXS7vJ0=; b=xzbfKm+oZEvvIE0WDoXQfpTdBb Pq2I6uFcGKner7CBdCwS4SKEKTFVmdfaKq5AloErR36hHmFrDEpd2mtIH0wCTRI9vEaUlxEpLiXKV W31jkiF22JtDSy6d35B2JOqhxFXk6XZmVyeZGNXVyypzUxFRd+ga0e3sZhWpfK+ZHs/M=; Subject: Re: [PATCH v3 2/5] xen/common: Guard iommu symbols with CONFIG_HAS_PASSTHROUGH To: Jan Beulich , 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: Julien Grall Message-ID: Date: Tue, 18 May 2021 15:06:29 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <8e415cac-a8b3-67a6-2f7b-489b964ceb50@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit 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? Cheers, -- Julien Grall