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

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Date:   Thu, 24 Aug 2023 22:40:35 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Dexuan Cui <decui@...rosoft.com>, ak@...ux.intel.com,
        arnd@...db.de, bp@...en8.de, brijesh.singh@....com,
        dan.j.williams@...el.com, dave.hansen@...el.com,
        dave.hansen@...ux.intel.com, haiyangz@...rosoft.com, hpa@...or.com,
        jane.chu@...cle.com, kirill.shutemov@...ux.intel.com,
        kys@...rosoft.com, linux-hyperv@...r.kernel.org, luto@...nel.org,
        mingo@...hat.com, peterz@...radead.org, rostedt@...dmis.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, seanjc@...gle.com,
        tglx@...utronix.de, tony.luck@...el.com, wei.liu@...nel.org,
        Jason@...c4.com, nik.borisov@...e.com, mikelley@...rosoft.com
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, Tianyu.Lan@...rosoft.com,
        rick.p.edgecombe@...el.com, andavis@...hat.com, mheslin@...hat.com,
        vkuznets@...hat.com, xiaoyao.li@...el.com
Subject: Re: [PATCH v3 07/10] Drivers: hv: vmbus: Bring the post_msg_page back
 for TDX VMs with the paravisor



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@...rosoft.com>

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