linux-kernel - [PATCH v2 04/11] x86/pvh: Use fixed_percpu

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Date:   Thu, 26 Oct 2023 12:00:53 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Uros Bizjak <ubizjak@...il.com>,
        Brian Gerst <brgerst@...il.com>
Subject: [PATCH v2 04/11] x86/pvh: Use fixed_percpu_data for early boot GSBASE

Instead of having a private area for the stack canary, use
fixed_percpu_data for GSBASE like the native kernel.

Signed-off-by: Brian Gerst <brgerst@...il.com>
---
 arch/x86/platform/pvh/head.S | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index c4365a05ab83..be8d973c0528 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -96,8 +96,9 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 1:
 	/* Set base address in stack canary descriptor. */
 	mov $MSR_GS_BASE,%ecx
-	mov $_pa(canary), %eax
-	xor %edx, %edx
+	lea INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
+	mov %edx, %eax
+	shr $32, %rdx
 	wrmsr
 
 	call xen_prepare_pvh
@@ -156,8 +157,6 @@ SYM_DATA_START_LOCAL(gdt_start)
 SYM_DATA_END_LABEL(gdt_start, SYM_L_LOCAL, gdt_end)
 
 	.balign 16
-SYM_DATA_LOCAL(canary, .fill 48, 1, 0)
-
 SYM_DATA_START_LOCAL(early_stack)
 	.fill BOOT_STACK_SIZE, 1, 0
 SYM_DATA_END_LABEL(early_stack, SYM_L_LOCAL, early_stack_end)
-- 
2.41.0