Re: [PATCH v3 07/10] Drivers: hv: vmbus: Bring the post_msg_page back for TDX VMs with the paravisor

Tianyu Lan
2023-08-24T14:41:45Z

On 8/24/2023 4:07 PM, Dexuan Cui wrote:
> The post_msg_page was removed in
> commit 9a6b1a170ca8 ("Drivers: hv: vmbus: Remove the per-CPU post_msg_page")
>
> However, it turns out that we need to bring it back, but only for a TDX VM
> with the paravisor: in such a VM, the hyperv_pcpu_input_arg is not decrypted,
> but the HVCALL_POST_MESSAGE in such a VM needs a decrypted page as the
> hypercall input page: see the comments in hyperv_init() for a detailed
> explanation.
>
> Except for HVCALL_POST_MESSAGE and HVCALL_SIGNAL_EVENT, the other hypercalls
> in a TDX VM with the paravisor still use hv_hypercall_pg and must use the
> hyperv_pcpu_input_arg (which is encrypted in such a VM), when a hypercall
> input page is used.
>
> Signed-off-by: Dexuan Cui <decui@microsoft.com>

Reviewed-by: Tianyu Lan <tiala@microsoft.com>