linux-kernel - [tip: x86/seves] x86/boot/compressed/64: Call set_sev_encryption

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Date:   Thu, 10 Sep 2020 09:22:24 -0000
From:   "tip-bot2 for Joerg Roedel" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...e.de>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/seves] x86/boot/compressed/64: Call
 set_sev_encryption_mask() earlier

The following commit has been merged into the x86/seves branch of tip:

Commit-ID:     c2a0304a286f386e45cea3f4b0617f0813de67fd
Gitweb:        https://git.kernel.org/tip/c2a0304a286f386e45cea3f4b0617f0813de67fd
Author:        Joerg Roedel <jroedel@...e.de>
AuthorDate:    Mon, 07 Sep 2020 15:15:21 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Mon, 07 Sep 2020 19:45:25 +02:00

x86/boot/compressed/64: Call set_sev_encryption_mask() earlier

Call set_sev_encryption_mask() while still on the stage 1 #VC-handler
because the stage 2 handler needs the kernel's own page tables to be
set up, to which calling set_sev_encryption_mask() is a prerequisite.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-21-joro@8bytes.org
---
 arch/x86/boot/compressed/head_64.S      |  9 ++++++++-
 arch/x86/boot/compressed/ident_map_64.c |  3 ---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index fb6c039..42190c0 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -543,9 +543,16 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 	rep	stosq
 
 /*
- * Load stage2 IDT and switch to our own page-table
+ * If running as an SEV guest, the encryption mask is required in the
+ * page-table setup code below. When the guest also has SEV-ES enabled
+ * set_sev_encryption_mask() will cause #VC exceptions, but the stage2
+ * handler can't map its GHCB because the page-table is not set up yet.
+ * So set up the encryption mask here while still on the stage1 #VC
+ * handler. Then load stage2 IDT and switch to the kernel's own
+ * page-table.
  */
 	pushq	%rsi
+	call	set_sev_encryption_mask
 	call	load_stage2_idt
 	call	initialize_identity_maps
 	popq	%rsi
diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index 62e42c1..b4f2a5f 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -105,9 +105,6 @@ static void add_identity_map(unsigned long start, unsigned long end)
 /* Locates and clears a region for a new top level page table. */
 void initialize_identity_maps(void)
 {
-	/* If running as an SEV guest, the encryption mask is required. */
-	set_sev_encryption_mask();
-
 	/* Exclude the encryption mask from __PHYSICAL_MASK */
 	physical_mask &= ~sme_me_mask;