From: David Gibson <david@gibson.dropbear.id.au> To: Christoph Hellwig <hch@lst.de> Cc: Ram Pai <linuxram@us.ibm.com>, "Michael S. Tsirkin" <mst@redhat.com>, Thiago Jung Bauermann <bauerman@linux.ibm.com>, virtualization@lists.linux-foundation.org, linuxppc-devel@lists.ozlabs.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jason Wang <jasowang@redhat.com>, Alexey Kardashevskiy <aik@linux.ibm.com>, Paul Mackerras <paulus@ozlabs.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org> Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Date: Mon, 12 Aug 2019 19:51:56 +1000 [thread overview] Message-ID: <20190812095156.GD3947@umbus.fritz.box> (raw) In-Reply-To: <20190811055607.GA12488@lst.de> [-- Attachment #1: Type: text/plain, Size: 2064 bytes --] On Sun, Aug 11, 2019 at 07:56:07AM +0200, Christoph Hellwig wrote: > sev_active() is gone now in linux-next, at least as a global API. > > And once again this is entirely going in the wrong direction. The only > way using the DMA API is going to work at all is if the device is ready > for it. So we need a flag on the virtio device, exposed by the > hypervisor (or hardware for hw virtio devices) that says: hey, I'm real, > don't take a shortcut. There still seems to be a failure to understand each other here. The limitation here simply *is not* a property of the device. In fact, it's effectively a property of the memory the virtio device would be trying to access (because it's in secure mode it can't be directly accessed via the hypervisor). There absolutely are cases where this is a device property (a physical virtio device being the obvious one), but this isn't one of them. Unfortunately, we're kind of stymied by the feature negotiation model of virtio. AIUI the hypervisor / device presents a bunch of feature bits of which the guest / driver selects a subset. AFAICT we already kind of abuse this for the VIRTIO_F_IOMMU_PLATFORM, because to handle for cases where it *is* a device limitation, we assume that if the hypervisor presents VIRTIO_F_IOMMU_PLATFORM then the guest *must* select it. What we actually need here is for the hypervisor to present VIRTIO_F_IOMMU_PLATFORM as available, but not required. Then we need a way for the platform core code to communicate to the virtio driver that *it* requires the IOMMU to be used, so that the driver can select or not the feature bit on that basis. > And that means on power and s390 qemu will always have to set thos if > you want to be ready for the ultravisor and co games. It's not like we > haven't been through this a few times before, have we? -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 833 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: David Gibson <david@gibson.dropbear.id.au> To: Christoph Hellwig <hch@lst.de> Cc: "Michael S. Tsirkin" <mst@redhat.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Jason Wang <jasowang@redhat.com>, Alexey Kardashevskiy <aik@linux.ibm.com>, Ram Pai <linuxram@us.ibm.com>, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Paul Mackerras <paulus@ozlabs.org>, iommu@lists.linux-foundation.org, linuxppc-devel@lists.ozlabs.org Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Date: Mon, 12 Aug 2019 19:51:56 +1000 [thread overview] Message-ID: <20190812095156.GD3947@umbus.fritz.box> (raw) In-Reply-To: <20190811055607.GA12488@lst.de> [-- Attachment #1.1: Type: text/plain, Size: 2064 bytes --] On Sun, Aug 11, 2019 at 07:56:07AM +0200, Christoph Hellwig wrote: > sev_active() is gone now in linux-next, at least as a global API. > > And once again this is entirely going in the wrong direction. The only > way using the DMA API is going to work at all is if the device is ready > for it. So we need a flag on the virtio device, exposed by the > hypervisor (or hardware for hw virtio devices) that says: hey, I'm real, > don't take a shortcut. There still seems to be a failure to understand each other here. The limitation here simply *is not* a property of the device. In fact, it's effectively a property of the memory the virtio device would be trying to access (because it's in secure mode it can't be directly accessed via the hypervisor). There absolutely are cases where this is a device property (a physical virtio device being the obvious one), but this isn't one of them. Unfortunately, we're kind of stymied by the feature negotiation model of virtio. AIUI the hypervisor / device presents a bunch of feature bits of which the guest / driver selects a subset. AFAICT we already kind of abuse this for the VIRTIO_F_IOMMU_PLATFORM, because to handle for cases where it *is* a device limitation, we assume that if the hypervisor presents VIRTIO_F_IOMMU_PLATFORM then the guest *must* select it. What we actually need here is for the hypervisor to present VIRTIO_F_IOMMU_PLATFORM as available, but not required. Then we need a way for the platform core code to communicate to the virtio driver that *it* requires the IOMMU to be used, so that the driver can select or not the feature bit on that basis. > And that means on power and s390 qemu will always have to set thos if > you want to be ready for the ultravisor and co games. It's not like we > haven't been through this a few times before, have we? -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 833 bytes --] [-- Attachment #2: Type: text/plain, Size: 156 bytes --] _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2019-08-12 13:54 UTC|newest] Thread overview: 198+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-01-29 17:08 [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Thiago Jung Bauermann 2019-01-29 17:08 ` Thiago Jung Bauermann 2019-01-29 17:42 ` Thiago Jung Bauermann 2019-01-29 17:42 ` Thiago Jung Bauermann 2019-01-29 19:02 ` Michael S. Tsirkin 2019-01-29 19:02 ` Michael S. Tsirkin 2019-01-30 2:24 ` Jason Wang 2019-01-30 2:24 ` Jason Wang 2019-01-30 2:36 ` Michael S. Tsirkin 2019-01-30 2:36 ` Michael S. Tsirkin 2019-01-30 2:36 ` Michael S. Tsirkin 2019-01-30 3:05 ` Jason Wang 2019-01-30 3:05 ` Jason Wang 2019-01-30 3:05 ` Jason Wang 2019-01-30 3:26 ` Michael S. Tsirkin 2019-01-30 3:26 ` Michael S. Tsirkin 2019-01-30 3:26 ` Michael S. Tsirkin 2019-01-30 7:44 ` Christoph Hellwig 2019-01-30 7:44 ` Christoph Hellwig 2019-01-30 7:44 ` Christoph Hellwig 2019-02-04 18:15 ` Thiago Jung Bauermann 2019-02-04 18:15 ` Thiago Jung Bauermann 2019-02-04 18:15 ` Thiago Jung Bauermann 2019-02-04 21:38 ` Michael S. Tsirkin 2019-02-04 21:38 ` Michael S. Tsirkin 2019-02-05 7:24 ` Christoph Hellwig 2019-02-05 7:24 ` Christoph Hellwig 2019-02-05 16:13 ` Michael S. Tsirkin 2019-02-05 16:13 ` Michael S. Tsirkin 2019-02-05 16:13 ` Michael S. Tsirkin 2019-02-05 16:13 ` Michael S. Tsirkin 2019-02-05 7:24 ` Christoph Hellwig 2019-02-04 21:38 ` Michael S. Tsirkin 2019-03-26 16:53 ` Michael S. Tsirkin 2019-03-26 16:53 ` Michael S. Tsirkin 2019-03-26 16:53 ` Michael S. Tsirkin 2019-01-30 2:24 ` Jason Wang 2019-02-04 18:14 ` Thiago Jung Bauermann 2019-02-04 18:14 ` Thiago Jung Bauermann 2019-02-04 18:14 ` Thiago Jung Bauermann 2019-02-04 20:23 ` Michael S. Tsirkin 2019-02-04 20:23 ` Michael S. Tsirkin 2019-03-20 16:13 ` Thiago Jung Bauermann 2019-03-20 16:13 ` Thiago Jung Bauermann 2019-03-20 16:13 ` Thiago Jung Bauermann 2019-03-20 21:17 ` Michael S. Tsirkin 2019-03-20 21:17 ` Michael S. Tsirkin 2019-03-20 21:17 ` Michael S. Tsirkin 2019-03-22 0:05 ` Thiago Jung Bauermann 2019-03-22 0:05 ` Thiago Jung Bauermann 2019-03-22 0:05 ` Thiago Jung Bauermann 2019-03-23 21:01 ` Michael S. Tsirkin 2019-03-23 21:01 ` Michael S. Tsirkin 2019-03-23 21:01 ` Michael S. Tsirkin 2019-03-25 0:57 ` David Gibson 2019-03-25 0:57 ` David Gibson 2019-03-25 0:57 ` David Gibson 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-17 21:42 ` Thiago Jung Bauermann 2019-04-19 23:09 ` Michael S. Tsirkin 2019-04-19 23:09 ` Michael S. Tsirkin 2019-04-19 23:09 ` Michael S. Tsirkin 2019-04-19 23:09 ` Michael S. Tsirkin 2019-04-25 1:01 ` Thiago Jung Bauermann 2019-04-25 1:01 ` Thiago Jung Bauermann 2019-04-25 1:01 ` Thiago Jung Bauermann 2019-04-25 1:18 ` Michael S. Tsirkin 2019-04-25 1:18 ` Michael S. Tsirkin 2019-04-25 1:18 ` Michael S. Tsirkin 2019-04-25 1:18 ` Michael S. Tsirkin 2019-04-25 1:18 ` Michael S. Tsirkin 2019-04-26 23:56 ` Thiago Jung Bauermann 2019-04-26 23:56 ` Thiago Jung Bauermann 2019-04-26 23:56 ` Thiago Jung Bauermann 2019-04-26 23:56 ` Thiago Jung Bauermann 2019-05-20 13:08 ` Michael S. Tsirkin 2019-05-20 13:08 ` Michael S. Tsirkin 2019-05-20 13:08 ` Michael S. Tsirkin 2019-05-20 13:08 ` Michael S. Tsirkin 2019-04-25 1:01 ` Thiago Jung Bauermann 2019-05-20 13:16 ` Michael S. Tsirkin 2019-05-20 13:16 ` Michael S. Tsirkin 2019-05-20 13:16 ` Michael S. Tsirkin 2019-05-20 13:16 ` Michael S. Tsirkin 2019-06-04 1:13 ` Thiago Jung Bauermann 2019-06-04 1:13 ` Thiago Jung Bauermann 2019-06-04 1:13 ` Thiago Jung Bauermann 2019-06-04 1:42 ` Michael S. Tsirkin 2019-06-04 1:42 ` Michael S. Tsirkin 2019-06-04 1:42 ` Michael S. Tsirkin 2019-06-04 1:42 ` Michael S. Tsirkin 2019-06-28 1:58 ` Thiago Jung Bauermann 2019-06-28 1:58 ` Thiago Jung Bauermann 2019-06-28 1:58 ` Thiago Jung Bauermann 2019-06-28 1:58 ` Thiago Jung Bauermann 2019-07-01 14:17 ` Michael S. Tsirkin 2019-07-01 14:17 ` Michael S. Tsirkin 2019-07-01 14:17 ` Michael S. Tsirkin 2019-07-01 14:17 ` Michael S. Tsirkin 2019-07-14 5:51 ` Thiago Jung Bauermann 2019-07-14 5:51 ` Thiago Jung Bauermann 2019-07-14 5:51 ` Thiago Jung Bauermann 2019-07-14 5:51 ` Thiago Jung Bauermann 2019-07-15 14:35 ` Michael S. Tsirkin 2019-07-15 14:35 ` Michael S. Tsirkin 2019-07-15 14:35 ` Michael S. Tsirkin 2019-07-15 14:35 ` Michael S. Tsirkin 2019-07-15 20:29 ` Thiago Jung Bauermann 2019-07-15 20:29 ` Thiago Jung Bauermann 2019-07-15 20:29 ` Thiago Jung Bauermann 2019-07-15 20:36 ` Michael S. Tsirkin 2019-07-15 20:36 ` Michael S. Tsirkin 2019-07-15 20:36 ` Michael S. Tsirkin 2019-07-15 20:36 ` Michael S. Tsirkin 2019-07-15 22:03 ` Thiago Jung Bauermann 2019-07-15 22:03 ` Thiago Jung Bauermann 2019-07-15 22:03 ` Thiago Jung Bauermann 2019-07-15 22:03 ` Thiago Jung Bauermann 2019-07-15 22:16 ` Michael S. Tsirkin 2019-07-15 22:16 ` Michael S. Tsirkin 2019-07-15 22:16 ` Michael S. Tsirkin 2019-07-15 22:16 ` Michael S. Tsirkin 2019-07-15 23:05 ` Thiago Jung Bauermann 2019-07-15 23:05 ` Thiago Jung Bauermann 2019-07-15 23:05 ` Thiago Jung Bauermann 2019-07-15 23:05 ` Thiago Jung Bauermann 2019-07-15 23:24 ` Benjamin Herrenschmidt 2019-07-15 23:24 ` Benjamin Herrenschmidt 2019-07-15 23:24 ` Benjamin Herrenschmidt 2019-07-15 23:24 ` Benjamin Herrenschmidt 2019-07-15 20:29 ` Thiago Jung Bauermann 2019-07-18 3:39 ` Thiago Jung Bauermann 2019-07-18 3:39 ` Thiago Jung Bauermann 2019-07-18 3:39 ` Thiago Jung Bauermann 2019-06-04 1:13 ` Thiago Jung Bauermann 2019-03-20 16:13 ` Thiago Jung Bauermann 2019-02-04 20:23 ` Michael S. Tsirkin 2019-01-29 19:02 ` Michael S. Tsirkin 2019-01-29 17:42 ` Thiago Jung Bauermann 2019-08-10 18:57 ` Michael S. Tsirkin 2019-08-10 18:57 ` Michael S. Tsirkin 2019-08-10 18:57 ` Michael S. Tsirkin 2019-08-10 22:07 ` Ram Pai 2019-08-10 22:07 ` Ram Pai 2019-08-10 22:07 ` Ram Pai 2019-08-11 5:56 ` Christoph Hellwig 2019-08-11 5:56 ` Christoph Hellwig 2019-08-11 5:56 ` Christoph Hellwig 2019-08-11 6:46 ` Ram Pai 2019-08-11 6:46 ` Ram Pai 2019-08-11 6:46 ` Ram Pai 2019-08-11 8:44 ` Michael S. Tsirkin 2019-08-11 8:44 ` Michael S. Tsirkin 2019-08-11 8:44 ` Michael S. Tsirkin 2019-08-12 12:13 ` Christoph Hellwig 2019-08-12 12:13 ` Christoph Hellwig 2019-08-12 12:13 ` Christoph Hellwig 2019-08-12 20:29 ` Ram Pai 2019-08-12 20:29 ` Ram Pai 2019-08-12 20:29 ` Ram Pai 2019-08-11 8:42 ` Michael S. Tsirkin 2019-08-11 8:42 ` Michael S. Tsirkin 2019-08-11 8:42 ` Michael S. Tsirkin 2019-08-11 8:55 ` Michael S. Tsirkin 2019-08-11 8:55 ` Michael S. Tsirkin 2019-08-11 8:55 ` Michael S. Tsirkin 2019-08-12 12:15 ` Christoph Hellwig 2019-08-12 12:15 ` Christoph Hellwig 2019-08-12 12:15 ` Christoph Hellwig 2019-09-06 5:07 ` Michael S. Tsirkin 2019-09-06 5:07 ` Michael S. Tsirkin 2019-09-06 5:07 ` Michael S. Tsirkin 2019-08-12 9:51 ` David Gibson 2019-08-12 9:51 ` David Gibson [this message] 2019-08-12 9:51 ` David Gibson 2019-08-13 13:26 ` Christoph Hellwig 2019-08-13 13:26 ` Christoph Hellwig 2019-08-13 14:24 ` David Gibson 2019-08-13 14:24 ` David Gibson 2019-08-13 15:45 ` Ram Pai 2019-08-13 15:45 ` Ram Pai 2019-08-13 15:45 ` Ram Pai 2019-08-26 17:48 ` Ram Pai 2019-08-26 17:48 ` Ram Pai 2019-08-26 17:48 ` Ram Pai 2019-08-13 14:24 ` David Gibson 2019-08-13 13:26 ` Christoph Hellwig 2019-08-11 8:12 ` Michael S. Tsirkin 2019-08-11 8:12 ` Michael S. Tsirkin 2019-08-11 8:12 ` Michael S. Tsirkin -- strict thread matches above, loose matches on Subject: below -- 2019-01-29 17:08 Thiago Jung Bauermann
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