diff mbox series

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

Message ID 1668624097-14884-7-git-send-email-mikelley@microsoft.com
State New
Headers
Series Add PCI pass-thru support to Hyper-V Confidential VMs |

Commit Message

Michael Kelley (LINUX) Nov. 16, 2022, 6:41 p.m. UTC 
  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>
---
 init/main.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

Comments

Tom Lendacky Nov. 16, 2022, 9:14 p.m. UTC | #1 
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
Borislav Petkov Nov. 21, 2022, 2:46 p.m. UTC | #2 
On Wed, Nov 16, 2022 at 10:41:29AM -0800, Michael Kelley wrote:
> 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.

I hope you're right. Our boot ordering is fragile as hell. But
mem_encrypt_init() doesn't do a whole lot of important setup - that has
happened a lot earlier already - so I'm not too worried.

But we'll see what breaks in wider testing.
diff mbox series

Patch

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