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[0/4] KVM: arm64: writable MIDR/REVIDR

Message ID 20250210154953.27002-1-sebott@redhat.com (mailing list archive)
Headers show
Series KVM: arm64: writable MIDR/REVIDR | expand

Message

Sebastian Ott Feb. 10, 2025, 3:49 p.m. UTC 
Based on prior discussion [1] this series allows VMMs to change
MIDR/REVIDR to enable migration between machines that differ in
these registers. Since these are used for errata handling the
errata management series [2] is a prerequisite for this one.

Note that guest access to MIDR_EL1 is not trapped.

[1] https://lore.kernel.org/kvmarm/20250124151732.6072-1-shameerali.kolothum.thodi@huawei.com/T/#mb855bc51714095a164a7b26bb8bead1606e4b753
[2] https://lore.kernel.org/kvmarm/20250205132222.55816-1-shameerali.kolothum.thodi@huawei.com/T/

Sebastian Ott (4):
  KVM: arm64: Allow userspace to change MIDR_EL1
  KVM: arm64: Allow userspace to change REVIDR_EL1
  KVM: arm64: Allow userspace to change AIDR_EL1
  KVM: arm64: trap guest access for REVIDR_EL1 and AIDR_EL1

 arch/arm64/include/asm/kvm_host.h |   9 ++
 arch/arm64/kvm/sys_regs.c         | 134 +++++++++++-------------------
 2 files changed, 56 insertions(+), 87 deletions(-)

Comments

Oliver Upton Feb. 10, 2025, 6:16 p.m. UTC | #1 
On Mon, Feb 10, 2025 at 04:49:49PM +0100, Sebastian Ott wrote:
> Based on prior discussion [1] this series allows VMMs to change
> MIDR/REVIDR to enable migration between machines that differ in
> these registers. Since these are used for errata handling the
> errata management series [2] is a prerequisite for this one.
> 
> Note that guest access to MIDR_EL1 is not trapped.
> 
> [1] https://lore.kernel.org/kvmarm/20250124151732.6072-1-shameerali.kolothum.thodi@huawei.com/T/#mb855bc51714095a164a7b26bb8bead1606e4b753
> [2] https://lore.kernel.org/kvmarm/20250205132222.55816-1-shameerali.kolothum.thodi@huawei.com/T/
> 
> Sebastian Ott (4):
>   KVM: arm64: Allow userspace to change MIDR_EL1
>   KVM: arm64: Allow userspace to change REVIDR_EL1
>   KVM: arm64: Allow userspace to change AIDR_EL1
>   KVM: arm64: trap guest access for REVIDR_EL1 and AIDR_EL1

Please reorganize the series such that guest accesses to REVIDR/AIDR are
trapped as soon as we allow userspace to change them. Also, can you
extend the set_id_regs selftest to assert that the guest sees the
correct value for these registers?