linux-kernel - [PATCH] x86/xen/pvh: Enable PAE mode for 32-bit guest only when CONFIG_X86

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Message-Id: <8c5448eeebbba998a7fff9ed9b2f7e7f3e437967.1697792461.git.houwenlong.hwl@antgroup.com>
Date:   Fri, 20 Oct 2023 17:08:42 +0800
From:   "Hou Wenlong" <houwenlong.hwl@...group.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Hou Wenlong" <houwenlong.hwl@...group.com>,
        "Juergen Gross" <jgross@...e.com>,
        "Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
        "Darren Hart" <dvhart@...radead.org>,
        "Andy Shevchenko" <andy@...radead.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" 
        <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        "moderated list:XEN HYPERVISOR X86" 
        <xen-devel@...ts.xenproject.org>,
        "open list:X86 PLATFORM DRIVERS - ARCH" 
        <platform-driver-x86@...r.kernel.org>
Subject: [PATCH] x86/xen/pvh: Enable PAE mode for 32-bit guest only when CONFIG_X86_PAE is set

The PVH entry is available for 32-bit KVM guests, and 32-bit KVM guests
do not depend on CONFIG_X86_PAE. However, mk_early_pgtbl_32() builds
different pagetables depending on whether CONFIG_X86_PAE is set.
Therefore, enabling PAE mode for 32-bit KVM guests without
CONFIG_X86_PAE being set would result in a boot failure during CR3
loading.

Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/platform/pvh/head.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index c4365a05ab83..085adb1b2313 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -70,10 +70,12 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 
 	mov $_pa(early_stack_end), %esp
 
+#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
 	/* Enable PAE mode. */
 	mov %cr4, %eax
 	orl $X86_CR4_PAE, %eax
 	mov %eax, %cr4
+#endif
 
 #ifdef CONFIG_X86_64
 	/* Enable Long mode. */
-- 
2.31.1