From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from blyat.fensystems.co.uk (blyat.fensystems.co.uk [54.246.183.96]) by mx.groups.io with SMTP id smtpd.web10.8571.1625228498205430649 for ; Fri, 02 Jul 2021 05:21:39 -0700 Authentication-Results: mx.groups.io; dkim=missing; spf=pass (domain: ipxe.org, ip: 54.246.183.96, mailfrom: mcb30@ipxe.org) Received: from pudding.home (unknown [188.94.42.109]) by blyat.fensystems.co.uk (Postfix) with ESMTPSA id 3BC2244186; Fri, 2 Jul 2021 12:21:34 +0000 (UTC) Subject: Re: [edk2-devel] [PATCH v2 1/2] OvmfPkg/Bhyve: add USB support To: Peter Grehan , devel@edk2.groups.io, c.koehne@beckhoff.com Cc: =?UTF-8?Q?Patrick_Br=c3=bcnn?= , "lersek@redhat.com" , "ardb+tianocore@kernel.org" , "jordan.l.justen@intel.com" , "rebecca@bsdio.com" References: <20210624060516.211-1-c.koehne@beckhoff.com> <20210624060516.211-2-c.koehne@beckhoff.com> <8f3f6360-a43e-c83d-b7dd-82d5600a1e28@freebsd.org> <6bde32cf8a874824a1bbd78b75f06adb@beckhoff.com> <981fe2fe-5f69-bb57-dd32-4bafbb841989@freebsd.org> <8a8b3161-0349-76c3-9a50-f24dc5f0b67c@ipxe.org> <848fb5ee-6e52-eed1-0b0d-39e4dda5c5dc@freebsd.org> From: "Michael Brown" Message-ID: Date: Fri, 2 Jul 2021 13:21:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <848fb5ee-6e52-eed1-0b0d-39e4dda5c5dc@freebsd.org> X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on blyat.fensystems.co.uk Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 02/07/2021 00:31, Peter Grehan wrote: >>>>> =C2=A0 bhyve doesn't (and will likely never) support Uhci/Ehci=20 >>>>> controllers so those lines can be removed. >>>> >>>> Is it possible to pass such a controller by PCI-Passthrough to a VM? >>>> If it's possible, I would keep these lines. >>> >>> =C2=A0=C2=A0Uhci/Ehci only support legacy interrupts and that isn't s= upported=20 >>> by bhyve PCI passthru. >> >> Is that a detail of the current implementation, or a fundamental=20 >> limitation in the bhyve architecture? >=20 > =C2=A0Only two choices ? :) Maybe half way between those points. When there is no fundamental limitation, i.e. when a future version of=20 the hypervisor may be able to support the feature with no changes to the=20 firmware, then it would be good practice to leave the drivers enabled.=20 Doing so avoids creating an unnecessarily tight coupling between the=20 hypervisor and firmware versions. More importantly: does it even matter that the hypervisor doesn't=20 support passthrough of PCI legacy interrupts? UEFI operates on a=20 polling basis, with the only active interrupt being some kind of=20 periodic timer. Where do you see any requirement for legacy interrupts=20 in the UHCI/EHCI drivers? Thanks, Michael