Re: [PATCH 01/13] x86/HV: Initialize GHCB page in Isolation VM

[Joerg Roedel <joro@xxxxxxxxxx>]

On Wed, Jul 28, 2021 at 10:52:16AM -0400, Tianyu Lan wrote:
> +static int hyperv_init_ghcb(void)
> +{
> +     u64 ghcb_gpa;
> +     void *ghcb_va;
> +     void **ghcb_base;
> +
> +     if (!ms_hyperv.ghcb_base)
> +             return -EINVAL;
> +
> +     rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
> +     ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);

This deserves a comment. As I understand it, the GHCB pa is set by
Hyper-V or the paravisor, so the page does not need to be allocated by
Linux.
And it is not mapped unencrypted because the GHCB page is allocated
above the VTOM boundary?

> @@ -167,6 +190,31 @@ static int hv_cpu_die(unsigned int cpu)
>  {
>       struct hv_reenlightenment_control re_ctrl;
>       unsigned int new_cpu;
> +     unsigned long flags;
> +     void **input_arg;
> +     void *pg;
> +     void **ghcb_va = NULL;
> +
> +     local_irq_save(flags);
> +     input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> +     pg = *input_arg;

Pg is never used later on, why is it set?