[v2] KVM: Fix race between reboot and hardware enabling

[PATCH v2 0/2] KVM: Fix race between reboot and hardware enabling

Posted by Sean Christopherson 2 years, 9 months ago

Fix a bug where enabling hardware virtualization can race with a forced
reboot, e.g. `reboot -f`, and result in virt hardware being enabled when
the reboot is attempted, and thus hanging the reboot.

Found by inspection, confirmed by hacking the reboot flow to wait until
KVM loads (the problematic window is ridiculously small).

Fully tested only on x86, compile tested on other architectures.

v2:
 - Rename KVM's callback to kvm_shutdown() to match the hook. [Marc]
 - Don't add a spurious newline. [Marc]

v1: https://lore.kernel.org/all/20230310221414.811690-1-seanjc@google.com

Sean Christopherson (2):
  KVM: Use syscore_ops instead of reboot_notifier to hook
    restart/shutdown
  KVM: Don't enable hardware after a restart/shutdown is initiated

 virt/kvm/kvm_main.c | 43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)


base-commit: b3c98052d46948a8d65d2778c7f306ff38366aac
-- 
2.40.1.606.ga4b1b128d6-goog

Re: [PATCH v2 0/2] KVM: Fix race between reboot and hardware enabling

Posted by Paolo Bonzini 2 years, 8 months ago

On 5/13/23 01:31, Sean Christopherson wrote:
> Fix a bug where enabling hardware virtualization can race with a forced
> reboot, e.g. `reboot -f`, and result in virt hardware being enabled when
> the reboot is attempted, and thus hanging the reboot.
> 
> Found by inspection, confirmed by hacking the reboot flow to wait until
> KVM loads (the problematic window is ridiculously small).
> 
> Fully tested only on x86, compile tested on other architectures.
> 
> v2:
>   - Rename KVM's callback to kvm_shutdown() to match the hook. [Marc]
>   - Don't add a spurious newline. [Marc]
> 
> v1: https://lore.kernel.org/all/20230310221414.811690-1-seanjc@google.com
> 
> Sean Christopherson (2):
>    KVM: Use syscore_ops instead of reboot_notifier to hook
>      restart/shutdown
>    KVM: Don't enable hardware after a restart/shutdown is initiated
> 
>   virt/kvm/kvm_main.c | 43 +++++++++++++++++++++++++++----------------
>   1 file changed, 27 insertions(+), 16 deletions(-)
> 
> 
> base-commit: b3c98052d46948a8d65d2778c7f306ff38366aac

Queued, thanks.

Paolo

Re: [PATCH v2 0/2] KVM: Fix race between reboot and hardware enabling

Posted by Marc Zyngier 2 years, 8 months ago

On Sat, 13 May 2023 00:31:25 +0100,
Sean Christopherson <seanjc@google.com> wrote:
> 
> Fix a bug where enabling hardware virtualization can race with a forced
> reboot, e.g. `reboot -f`, and result in virt hardware being enabled when
> the reboot is attempted, and thus hanging the reboot.
> 
> Found by inspection, confirmed by hacking the reboot flow to wait until
> KVM loads (the problematic window is ridiculously small).
> 
> Fully tested only on x86, compile tested on other architectures.
> 
> v2:
>  - Rename KVM's callback to kvm_shutdown() to match the hook. [Marc]
>  - Don't add a spurious newline. [Marc]
> 
> v1: https://lore.kernel.org/all/20230310221414.811690-1-seanjc@google.com
> 
> Sean Christopherson (2):
>   KVM: Use syscore_ops instead of reboot_notifier to hook
>     restart/shutdown
>   KVM: Don't enable hardware after a restart/shutdown is initiated
> 
>  virt/kvm/kvm_main.c | 43 +++++++++++++++++++++++++++----------------
>  1 file changed, 27 insertions(+), 16 deletions(-)

Acked-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.