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

From: Tom Lendacky <thomas.lendacky@amd.com>
To: Michael Kelley <mikelley@microsoft.com>,
	hpa@zytor.com, kys@microsoft.com, haiyangz@microsoft.com,
	wei.liu@kernel.org, decui@microsoft.com, luto@kernel.org,
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Subject: Re: [Patch v3 06/14] init: Call mem_encrypt_init() after Hyper-V hypercall init is done
Date: Wed, 16 Nov 2022 15:14:17 -0600	[thread overview]
Message-ID: <b194eaa1-cc79-226f-b87b-3e58090ca08e@amd.com> (raw)
In-Reply-To: <1668624097-14884-7-git-send-email-mikelley@microsoft.com>

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@microsoft.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@amd.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