On Tue, May 23, 2023 at 10:14:21AM -0700, Michael Kelley wrote:
> These commits
>
> a494aef23dfc ("PCI: hv: Replace retarget_msi_interrupt_params with hyperv_pcpu_input_arg")
> 2c6ba4216844 ("PCI: hv: Enable PCI pass-thru devices in Confidential VMs")
>
> update the Hyper-V virtual PCI driver to use the hyperv_pcpu_input_arg
> because that memory will be correctly marked as decrypted or encrypted
> for all VM types (CoCo or normal). But problems ensue when CPUs in the
> VM go online or offline after virtual PCI devices have been configured.
>
> When a CPU is brought online, the hyperv_pcpu_input_arg for that CPU is
> initialized by hv_cpu_init() running under state CPUHP_AP_ONLINE_DYN.
> But this state occurs after state CPUHP_AP_IRQ_AFFINITY_ONLINE, which
> may call the virtual PCI driver and fault trying to use the as yet
> uninitialized hyperv_pcpu_input_arg. A similar problem occurs in a CoCo
> VM if the MMIO read and write hypercalls are used from state
> CPUHP_AP_IRQ_AFFINITY_ONLINE.
>
> When a CPU is taken offline, IRQs may be reassigned in state
> CPUHP_TEARDOWN_CPU. Again, the virtual PCI driver may fault trying to
> use the hyperv_pcpu_input_arg that has already been freed by a
> higher state.
>
> Fix the onlining problem by adding state CPUHP_AP_HYPERV_ONLINE
> immediately after CPUHP_AP_ONLINE_IDLE (similar to CPUHP_AP_KVM_ONLINE)
> and before CPUHP_AP_IRQ_AFFINITY_ONLINE. Use this new state for
> Hyper-V initialization so that hyperv_pcpu_input_arg is allocated
> early enough.
>
> Fix the offlining problem by not freeing hyperv_pcpu_input_arg when
> a CPU goes offline. Retain the allocated memory, and reuse it if
> the CPU comes back online later.
>
> Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> ---
>
> Changes in v2:
> * Put CPUHP_AP_HYPERV_ONLINE before CPUHP_AP_KVM_ONLINE [Vitaly
> Kuznetsov]
>
> arch/x86/hyperv/hv_init.c | 2 +-
> drivers/hv/hv_common.c | 48 +++++++++++++++++++++++-----------------------
> include/linux/cpuhotplug.h | 1 +
> 3 files changed, 26 insertions(+), 25 deletions(-)
Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
