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Date:   Mon, 2 Aug 2021 13:53:26 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
        jgross@...e.com, sstabellini@...nel.org, will@...nel.org,
        davem@...emloft.net, kuba@...nel.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, arnd@...db.de, hch@....de,
        m.szyprowski@...sung.com, robin.murphy@....com,
        thomas.lendacky@....com, brijesh.singh@....com, ardb@...nel.org,
        Tianyu.Lan@...rosoft.com, rientjes@...gle.com,
        martin.b.radev@...il.com, akpm@...ux-foundation.org,
        rppt@...nel.org, kirill.shutemov@...ux.intel.com,
        aneesh.kumar@...ux.ibm.com, krish.sadhukhan@...cle.com,
        saravanand@...com, xen-devel@...ts.xenproject.org,
        pgonda@...gle.com, david@...hat.com, keescook@...omium.org,
        hannes@...xchg.org, sfr@...b.auug.org.au,
        michael.h.kelley@...rosoft.com, iommu@...ts.linux-foundation.org,
        linux-arch@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        netdev@...r.kernel.org, vkuznets@...hat.com, anparri@...rosoft.com
Subject: Re: [PATCH 01/13] x86/HV: Initialize GHCB page in Isolation VM

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?

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