linux-kernel - Re: [Patch v3 06/14] init: Call mem_encrypt_init() after Hyper-V hypercall init is done

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Message-ID: <b194eaa1-cc79-226f-b87b-3e58090ca08e@amd.com>
Date:   Wed, 16 Nov 2022 15:14:17 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Michael Kelley <mikelley@...rosoft.com>, hpa@...or.com,
        kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, luto@...nel.org, peterz@...radead.org,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, lpieralisi@...nel.org, robh@...nel.org,
        kw@...ux.com, bhelgaas@...gle.com, arnd@...db.de,
        hch@...radead.org, m.szyprowski@...sung.com, robin.murphy@....com,
        brijesh.singh@....com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com,
        Tianyu.Lan@...rosoft.com, kirill.shutemov@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, dan.j.williams@...el.com,
        jane.chu@...cle.com, seanjc@...gle.com, tony.luck@...el.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
        iommu@...ts.linux.dev
Subject: Re: [Patch v3 06/14] init: Call mem_encrypt_init() after Hyper-V
 hypercall init is done

On 11/16/22 12:41, Michael Kelley wrote:
> Full Hyper-V initialization, including support for hypercalls, is done
> as an apic_post_init callback via late_time_init().  mem_encrypt_init()
> needs to make hypercalls when it marks swiotlb memory as decrypted.
> But mem_encrypt_init() is currently called a few lines before
> late_time_init(), so the hypercalls don't work.
> 
> Fix this by moving mem_encrypt_init() after late_time_init() and
> related clock initializations. The intervening initializations don't
> do any I/O that requires the swiotlb, so moving mem_encrypt_init()
> slightly later has no impact.
> 
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>

Some quick testing with mem_encrypt_init() in the new location hasn't 
shown any problems under SME/SEV.

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>   init/main.c | 19 +++++++++++--------
>   1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/init/main.c b/init/main.c
> index e1c3911..5a7c466 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1088,14 +1088,6 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
>   	 */
>   	locking_selftest();
>   
> -	/*
> -	 * This needs to be called before any devices perform DMA
> -	 * operations that might use the SWIOTLB bounce buffers. It will
> -	 * mark the bounce buffers as decrypted so that their usage will
> -	 * not cause "plain-text" data to be decrypted when accessed.
> -	 */
> -	mem_encrypt_init();
> -
>   #ifdef CONFIG_BLK_DEV_INITRD
>   	if (initrd_start && !initrd_below_start_ok &&
>   	    page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
> @@ -1112,6 +1104,17 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
>   		late_time_init();
>   	sched_clock_init();
>   	calibrate_delay();
> +
> +	/*
> +	 * This needs to be called before any devices perform DMA
> +	 * operations that might use the SWIOTLB bounce buffers. It will
> +	 * mark the bounce buffers as decrypted so that their usage will
> +	 * not cause "plain-text" data to be decrypted when accessed. It
> +	 * must be called after late_time_init() so that Hyper-V x86/x64
> +	 * hypercalls work when the SWIOTLB bounce buffers are decrypted.
> +	 */
> +	mem_encrypt_init();
> +
>   	pid_idr_init();
>   	anon_vma_init();
>   #ifdef CONFIG_X86