On 4/21/2025 9:31 AM, mhkelle...@gmail.com wrote:
> From: Michael Kelley <mhkli...@outlook.com>
>
> When a CPU goes offline, hv_common_cpu_die() frees the
> hv_synic_eventring_tail memory for the CPU. But in a normal VM (i.e., not
> running in the root partition) the per-CPU memory has not been allocated,
> resulting in a bad memory reference and oops when computing the argument
> to kfree().
>
> Fix this by freeing the memory only when running in the root partition.
>
> Fixes: 04df7ac39943 ("Drivers: hv: Introduce per-cpu event ring tail")
> Signed-off-by: Michael Kelley <mhkli...@outlook.com>
> ---
> drivers/hv/hv_common.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index b3b11be11650..8967010db86a 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -566,9 +566,11 @@ int hv_common_cpu_die(unsigned int cpu)
> * originally allocated memory is reused in hv_common_cpu_init().
> */
>
> - synic_eventring_tail = this_cpu_ptr(hv_synic_eventring_tail);
> - kfree(*synic_eventring_tail);
> - *synic_eventring_tail = NULL;
> + if (hv_root_partition()) {
> + synic_eventring_tail = this_cpu_ptr(hv_synic_eventring_tail);
> + kfree(*synic_eventring_tail);
> + *synic_eventring_tail = NULL;
> + }
>
> return 0;
> }
Reviewed-by: Nuno Das Neves <nunodasne...@linux.microsoft.com>
