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authorWei Huang <wei@redhat.com>2019-01-03 23:44:11 -0600
committerThomas Gleixner <tglx@linutronix.de>2019-01-29 21:58:59 +0100
commitb677dfae5aa197afc5191755a76a8727ffca538a (patch)
treece025b3d79a965312fe3a1356cfb4bc95f1f5e7b /arch
parent00ae831dfe4474ef6029558f5eb3ef0332d80043 (diff)
x86/boot/compressed/64: Set EFER.LME=1 in 32-bit trampoline before returning to long mode
In some old AMD KVM implementation, guest's EFER.LME bit is cleared by KVM when the hypervsior detects that the guest sets CR0.PG to 0. This causes the guest OS to reboot when it tries to return from 32-bit trampoline code because the CPU is in incorrect state: CR4.PAE=1, CR0.PG=1, CS.L=1, but EFER.LME=0. As a precaution, set EFER.LME=1 as part of long mode activation procedure. This extra step won't cause any harm when Linux is booted on a bare-metal machine. Signed-off-by: Wei Huang <wei@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: bp@alien8.de Cc: hpa@zytor.com Link: https://lkml.kernel.org/r/20190104054411.12489-1-wei@redhat.com
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/boot/compressed/head_64.S8
-rw-r--r--arch/x86/boot/compressed/pgtable.h2
2 files changed, 9 insertions, 1 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 64037895b085..f105ae8651c9 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -600,6 +600,14 @@ ENTRY(trampoline_32bit_src)
leal TRAMPOLINE_32BIT_PGTABLE_OFFSET(%ecx), %eax
movl %eax, %cr3
3:
+ /* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */
+ pushl %ecx
+ movl $MSR_EFER, %ecx
+ rdmsr
+ btsl $_EFER_LME, %eax
+ wrmsr
+ popl %ecx
+
/* Enable PAE and LA57 (if required) paging modes */
movl $X86_CR4_PAE, %eax
cmpl $0, %edx
diff --git a/arch/x86/boot/compressed/pgtable.h b/arch/x86/boot/compressed/pgtable.h
index 91f75638f6e6..6ff7e81b5628 100644
--- a/arch/x86/boot/compressed/pgtable.h
+++ b/arch/x86/boot/compressed/pgtable.h
@@ -6,7 +6,7 @@
#define TRAMPOLINE_32BIT_PGTABLE_OFFSET 0
#define TRAMPOLINE_32BIT_CODE_OFFSET PAGE_SIZE
-#define TRAMPOLINE_32BIT_CODE_SIZE 0x60
+#define TRAMPOLINE_32BIT_CODE_SIZE 0x70
#define TRAMPOLINE_32BIT_STACK_END TRAMPOLINE_32BIT_SIZE