| Message ID | 20200213005837.131791-1-david@gibson.dropbear.id.au (mailing list archive) |
|---|---|
| Headers | show |
| Series | spapr: Use vIOMMU translation for virtio by default | expand |
On Thu, 13 Feb 2020 11:58:35 +1100 David Gibson <david@gibson.dropbear.id.au> wrote: > Upcoming Secure VM support for pSeries machines introduces some > complications for virtio, since the transfer buffers need to be > explicitly shared so that the hypervisor can access them. > > While it's not strictly speaking dependent on it, the fact that virtio > devices bypass normal platform IOMMU translation complicates the issue > on the guest side. Since there are some significan downsides to > bypassing the vIOMMU anyway, let's just disable that. > > There's already a flag to do this in virtio, just turn it on by > default for forthcoming pseries machine types. > > Any opinions on whether dropping support for the older guest kernels > is acceptable at this point? > As expected, this breaks compatibility with existing RHEL 6.10 guests. Each patch in this series requires an extra -global option to be specified on the command line in order to boot successfully. Patch 1: -global virtio-pci.disable-legacy=auto Patch 2: -global virtio-pci.iommu_platform=off As seen on the RH site [1], RHEL6 will reach "End of Maintenance Support or Maintenance Support 2 (Product retirement)" on November 30, 2020 and "End of Extended Life-cycle Support" on June 30, 2024. Not sure if it's okay to drop support for RHEL6 this soon. RHEL 7.7 guests seem to be unaffected. [1] https://access.redhat.com/support/policy/updates/errata/#Life_Cycle_Dates > Changes since v1: > * Added information on which guest kernel versions will no longer > work with these changes > * Use Michael Tsirkin's suggested better way of handling the machine > type change > > David Gibson (2): > spapr: Disable legacy virtio devices for pseries-5.0 and later > spapr: Enable virtio iommu_platform=on by default > > hw/ppc/spapr.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) >
On Thu, Feb 13, 2020 at 12:46:43PM +0100, Greg Kurz wrote: > On Thu, 13 Feb 2020 11:58:35 +1100 > David Gibson <david@gibson.dropbear.id.au> wrote: > > > Upcoming Secure VM support for pSeries machines introduces some > > complications for virtio, since the transfer buffers need to be > > explicitly shared so that the hypervisor can access them. > > > > While it's not strictly speaking dependent on it, the fact that virtio > > devices bypass normal platform IOMMU translation complicates the issue > > on the guest side. Since there are some significan downsides to > > bypassing the vIOMMU anyway, let's just disable that. > > > > There's already a flag to do this in virtio, just turn it on by > > default for forthcoming pseries machine types. > > > > Any opinions on whether dropping support for the older guest kernels > > is acceptable at this point? > > > > As expected, this breaks compatibility with existing RHEL 6.10 guests. Each > patch in this series requires an extra -global option to be specified on > the command line in order to boot successfully. > > Patch 1: -global virtio-pci.disable-legacy=auto > Patch 2: -global virtio-pci.iommu_platform=off Right, or setting an older machine type. > As seen on the RH site [1], RHEL6 will reach "End of Maintenance Support > or Maintenance Support 2 (Product retirement)" on November 30, 2020 and > "End of Extended Life-cycle Support" on June 30, 2024. > > Not sure if it's okay to drop support for RHEL6 this soon. Hm, yeah. I'm happy enough to do this upstream, downstream will require some discussion. > RHEL 7.7 guests seem to be unaffected. Yeah, I already checked and RHEL7 has backported support for modern virtio and the iommu platform flag. > > [1] https://access.redhat.com/support/policy/updates/errata/#Life_Cycle_Dates > > > Changes since v1: > > * Added information on which guest kernel versions will no longer > > work with these changes > > * Use Michael Tsirkin's suggested better way of handling the machine > > type change > > > > David Gibson (2): > > spapr: Disable legacy virtio devices for pseries-5.0 and later > > spapr: Enable virtio iommu_platform=on by default > > > > hw/ppc/spapr.c | 16 +++++++++++++++- > > 1 file changed, 15 insertions(+), 1 deletion(-) > > >