hw/ppc/spapr.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
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? 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(-) -- 2.24.1
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(-) > > > -- 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
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