linux-kernel - RE: [PATCH v3 07/10] Drivers: hv: vmbus: Bring the post_msg

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Message-ID: <BYAPR21MB1688C7407CB6BA9A540F5683D71DA@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Thu, 24 Aug 2023 14:07:23 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Dexuan Cui <decui@...rosoft.com>,
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Subject: RE: [PATCH v3 07/10] Drivers: hv: vmbus: Bring the post_msg_page back
 for TDX VMs with the paravisor

From: Dexuan Cui <decui@...rosoft.com> Sent: Thursday, August 24, 2023 1:07 AM
> 
> 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@...rosoft.com>
> ---
> 
> Changes in v2: None
> 
> Changes in v3:
>   hyperv_paravisor_present -> ms_hyperv.paravisor_present
> 
>  arch/x86/hyperv/hv_init.c | 20 +++++++++++--
>  drivers/hv/hv.c           | 59 +++++++++++++++++++++++++++++++++++----
>  drivers/hv/hyperv_vmbus.h | 11 ++++++++
>  3 files changed, 82 insertions(+), 8 deletions(-)
> 

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>