lkml.org 
[lkml]   [2020]   [Oct]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v3 0/2] MTE support for KVM guest
From
Date
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@arm.com
>>
>> 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

\
 
 \ /
  Last update: 2020-10-02 17:39    [W:0.073 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site