Merge tag 'x86_sev_for_v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 SEV updates from Borislav Petkov:

 - Convert the sev-guest plaform ->remove callback to return void

 - Move the SEV C-bit verification to the BSP as it needs to happen only
   once and not on every AP

* tag 'x86_sev_for_v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  virt: sev-guest: Convert to platform remove callback returning void
  x86/sev: Do the C-bit verification only on the BSP

2 files changed, 24 insertions, 13 deletions

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 0f8103240fda..f479e5e793a2 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -114,6 +114,28 @@ SYM_CODE_START_NOALIGN(startup_64)
 
 	/* Form the CR3 value being sure to include the CR3 modifier */
 	addq	$(early_top_pgt - __START_KERNEL_map), %rax
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+	mov	%rax, %rdi
+	mov	%rax, %r14
+
+	addq	phys_base(%rip), %rdi
+
+	/*
+	 * For SEV guests: Verify that the C-bit is correct. A malicious
+	 * hypervisor could lie about the C-bit position to perform a ROP
+	 * attack on the guest by writing to the unencrypted stack and wait for
+	 * the next RET instruction.
+	 */
+	call	sev_verify_cbit
+
+	/*
+	 * Restore CR3 value without the phys_base which will be added
+	 * below, before writing %cr3.
+	 */
+	 mov	%r14, %rax
+#endif
+
 	jmp 1f
 SYM_CODE_END(startup_64)
 
@@ -193,15 +215,6 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	addq	phys_base(%rip), %rax
 
 	/*
-	 * For SEV guests: Verify that the C-bit is correct. A malicious
-	 * hypervisor could lie about the C-bit position to perform a ROP
-	 * attack on the guest by writing to the unencrypted stack and wait for
-	 * the next RET instruction.
-	 */
-	movq	%rax, %rdi
-	call	sev_verify_cbit
-
-	/*
 	 * Switch to new page-table
 	 *
 	 * For the boot CPU this switches to early_top_pgt which still has the
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index bc564adcf499..87f241825bc3 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -994,7 +994,7 @@ e_unmap:
 	return ret;
 }
 
-static int __exit sev_guest_remove(struct platform_device *pdev)
+static void __exit sev_guest_remove(struct platform_device *pdev)
 {
 	struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
 
@@ -1003,8 +1003,6 @@ static int __exit sev_guest_remove(struct platform_device *pdev)
 	free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
 	deinit_crypto(snp_dev->crypto);
 	misc_deregister(&snp_dev->misc);
-
-	return 0;
 }
 
 /*
@@ -1013,7 +1011,7 @@ static int __exit sev_guest_remove(struct platform_device *pdev)
  * with the SEV-SNP support, it is named "sev-guest".
  */
 static struct platform_driver sev_guest_driver = {
-	.remove		= __exit_p(sev_guest_remove),
+	.remove_new	= __exit_p(sev_guest_remove),
 	.driver		= {
 		.name = "sev-guest",
 	},