Re: [RFC PATCH V3 01/11] x86/HV: Initialize GHCB page in Isolation VM

[Joerg Roedel <joro@xxxxxxxxxx>]

On Sun, May 30, 2021 at 11:06:18AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> 
> Hyper-V exposes GHCB page via SEV ES GHCB MSR for SNP guest
> to communicate with hypervisor. Map GHCB page for all
> cpus to read/write MSR register and submit hvcall request
> via GHCB.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
>  arch/x86/hyperv/hv_init.c       | 60 ++++++++++++++++++++++++++++++---
>  arch/x86/include/asm/mshyperv.h |  2 ++
>  include/asm-generic/mshyperv.h  |  2 ++
>  3 files changed, 60 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index bb0ae4b5c00f..dc74d01cb859 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -60,6 +60,9 @@ static int hv_cpu_init(unsigned int cpu)
>       struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
>       void **input_arg;
>       struct page *pg;
> +     u64 ghcb_gpa;
> +     void *ghcb_va;
> +     void **ghcb_base;

Any reason you can't reuse the SEV-ES support code in the Linux kernel?
It already has code to setup GHCBs for all vCPUs.

I see that you don't need #VC handling in your SNP VMs because of the
paravisor running underneath it, but just re-using the GHCB setup code
shouldn't be too hard.

Regards,

        Joerg