On Fri, Oct 02, 2020 at 04:38:11PM +0100, Steven Price wrote: > On 02/10/2020 15:36, Andrew Jones wrote: > > On Fri, Sep 25, 2020 at 10:36:05AM +0100, Steven Price wrote: > > > Version 3 of adding MTE support for KVM guests. See the previous (v2) > > > posting for background: > > > > > > https://lore.kernel.org/r/20200904160018.29481-1-steven.price%40arm.com > > > > > > These patches add support to KVM to enable MTE within a guest. They are > > > based on Catalin's v9 MTE user-space support series[1] (currently in > > > next). > > > > > > Changes since v2: > > > > > > * MTE is no longer a VCPU feature, instead it is a VM cap. > > > > > > * Being a VM cap means easier probing (check for KVM_CAP_ARM_MTE). > > > > > > * The cap must be set before any VCPUs are created, preventing any > > > shenanigans where MTE is enabled for the guest after memory accesses > > > have been performed. > > > > > > [1] https://lore.kernel.org/r/20200904103029.32083-1-catalin.marinas@xxxxxxx > > > > > > Steven Price (2): > > > arm64: kvm: Save/restore MTE registers > > > arm64: kvm: Introduce MTE VCPU feature > > > > > > arch/arm64/include/asm/kvm_emulate.h | 3 +++ > > > arch/arm64/include/asm/kvm_host.h | 7 +++++++ > > > arch/arm64/include/asm/sysreg.h | 3 ++- > > > arch/arm64/kvm/arm.c | 9 +++++++++ > > > arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 14 ++++++++++++++ > > > arch/arm64/kvm/mmu.c | 15 +++++++++++++++ > > > arch/arm64/kvm/sys_regs.c | 20 +++++++++++++++----- > > > include/uapi/linux/kvm.h | 1 + > > > 8 files changed, 66 insertions(+), 6 deletions(-) > > > > > > -- > > > 2.20.1 > > > > > > > > > > Hi Steven, > > > > These patches look fine to me, but I'd prefer we have a working > > implementation in QEMU before we get too excited about the KVM > > bits. kvmtool isn't sufficient since it doesn't support migration > > (at least afaik). In the past we've implemented features in KVM > > that look fine, but then issues have been discovered when trying > > to enable them from QEMU, where we also support migration. This > > feature looks like there's risk of issues with the userspace side. > > Although these two patches would probably stay the same, even if > > userspace requires more support. > > I agree kvmtool isn't a great test because it doesn't support migration. The > support in this series is just the basic support for MTE in a guest and we'd > need to wait for the QEMU implementation before deciding whether we need any > extra support (e.g. kernel interfaces for reading/writing tags as discussed > before). > > However, I don't think there's much danger of the support in this series > changing - so extra support can be added when/if it's needed, but I don't > think we need to block these series on that - QEMU can just probe for > whatever additional support it needs before enabling MTE in a guest. I plan > to rebase/repost after -rc1 when the user space support has been merged. > Fair enough, but it feels like we'll be merging half a feature, leaving the other half for somebody else to pick up later. Thanks, drew _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
