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

[Tianyu Lan]

Hi Joerg:
     Thanks for your review.


On 8/2/2021 7:53 PM, Joerg Roedel wrote:
> 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?

You are right. The ghdb page is allocated by paravisor and its physical 
address is above VTOM boundary. Will add a comment to describe this.
Thanks for suggestion.

> > @@ -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?

Sorry for noise. This should be removed during rebase and will fix in 
the next version.