diff options
| author | Wei Huang <wei@redhat.com> | 2019-01-03 23:44:11 -0600 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-01-29 21:58:59 +0100 |
| commit | b677dfae5aa197afc5191755a76a8727ffca538a (patch) | |
| tree | ce025b3d79a965312fe3a1356cfb4bc95f1f5e7b /arch/x86/boot/compressed/head_64.S | |
| parent | 00ae831dfe4474ef6029558f5eb3ef0332d80043 (diff) | |
| download | blackbird-obmc-linux-b677dfae5aa197afc5191755a76a8727ffca538a.tar.gz blackbird-obmc-linux-b677dfae5aa197afc5191755a76a8727ffca538a.zip | |
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/x86/boot/compressed/head_64.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 8 |
1 files changed, 8 insertions, 0 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 |
