Re: [PATCH v3 0/4] KVM: arm64: Fix get-reg-list regression

[Dave Martin <Dave.Martin@arm.com>]

On Thu, Nov 05, 2020 at 10:10:18AM +0100, Andrew Jones wrote:
> 张东旭 <xu910121@sina.com> reported a regression seen with CentOS
> when migrating from an old kernel to a new one. The problem was
> that QEMU rejected the migration since KVM_GET_REG_LIST reported
> a register was missing on the destination. Extra registers are OK
> on the destination, but not missing ones. The regression reproduces
> with upstream kernels when migrating from a 4.15 or later kernel,
> up to one with commit 73433762fcae ("KVM: arm64/sve: System register
> context switch and access support"), to a kernel that includes that
> commit, e.g. the latest mainline (5.10-rc2).
> 
> The first patch of this series is the fix. The next two patches,
> which don't have any intended functional changes, allow ID_SANITISED
> to be used for registers that flip between exposing features and
> being RAZ, which allows some code to be removed.
> 
> v3:
>  - Improve commit messages [Dave]
>  - Add new patch to consolidate REG_HIDDEN* flags [Dave]
> 
> v2:
>  - CC stable [Marc]
>  - Only one RAZ flag is enough [Marc]
>  - Move id_visibility() up by read_id_reg() since they'll likely
>    be maintained together [drew]
> 
> 
> Andrew Jones (4):
>   KVM: arm64: Don't hide ID registers from userspace
>   KVM: arm64: Consolidate REG_HIDDEN_GUEST/USER
>   KVM: arm64: Check RAZ visibility in ID register accessors
>   KVM: arm64: Remove AA64ZFR0_EL1 accessors
> 
>  arch/arm64/kvm/sys_regs.c | 108 ++++++++++++--------------------------
>  arch/arm64/kvm/sys_regs.h |  16 +++---
>  2 files changed, 41 insertions(+), 83 deletions(-)

Thanks for the updates.

Looks like I missed the opportunity to review this, but just for the
record (even if it doesn't appear in the tree):

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

Cheers
---Dave
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