linux-kernel - [Patch v4 05/13] init: Call mem_encrypt_init() after Hyper-V hypercall init is done

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Message-Id: <1669951831-4180-6-git-send-email-mikelley@microsoft.com>
Date:   Thu,  1 Dec 2022 19:30:23 -0800
From:   Michael Kelley <mikelley@...rosoft.com>
To:     hpa@...or.com, kys@...rosoft.com, haiyangz@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com, luto@...nel.org,
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        iommu@...ts.linux.dev
Cc:     mikelley@...rosoft.com
Subject: [Patch v4 05/13] init: Call mem_encrypt_init() after Hyper-V hypercall init is done

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>
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
-- 
1.8.3.1