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.
Steve
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
