queue-4.20/x86-boot-compressed-64-set-efer.lme-1-in-32-bit-tram.patch

   1 From e9a0b4d1c6e2191daf89936395bff640d313bdbc Mon Sep 17 00:00:00 2001
   2 From: Wei Huang <wei@redhat.com>
   3 Date: Thu, 3 Jan 2019 23:44:11 -0600
   4 Subject: x86/boot/compressed/64: Set EFER.LME=1 in 32-bit trampoline before
   5  returning to long mode
   6
   7 [ Upstream commit b677dfae5aa197afc5191755a76a8727ffca538a ]
   8
   9 In some old AMD KVM implementation, guest's EFER.LME bit is cleared by KVM
  10 when the hypervsior detects that the guest sets CR0.PG to 0. This causes
  11 the guest OS to reboot when it tries to return from 32-bit trampoline code
  12 because the CPU is in incorrect state: CR4.PAE=1, CR0.PG=1, CS.L=1, but
  13 EFER.LME=0.  As a precaution, set EFER.LME=1 as part of long mode
  14 activation procedure. This extra step won't cause any harm when Linux is
  15 booted on a bare-metal machine.
  16
  17 Signed-off-by: Wei Huang <wei@redhat.com>
  18 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  19 Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
  20 Cc: bp@alien8.de
  21 Cc: hpa@zytor.com
  22 Link: https://lkml.kernel.org/r/20190104054411.12489-1-wei@redhat.com
  23 Signed-off-by: Sasha Levin <sashal@kernel.org>
  24 ---
  25  arch/x86/boot/compressed/head_64.S | 8 ++++++++
  26  arch/x86/boot/compressed/pgtable.h | 2 +-
  27  2 files changed, 9 insertions(+), 1 deletion(-)
  28
  29 diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
  30 index 64037895b085..f105ae8651c9 100644
  31 --- a/arch/x86/boot/compressed/head_64.S
  32 +++ b/arch/x86/boot/compressed/head_64.S
  33 @@ -600,6 +600,14 @@ ENTRY(trampoline_32bit_src)
  34         leal    TRAMPOLINE_32BIT_PGTABLE_OFFSET(%ecx), %eax
  35         movl    %eax, %cr3
  36  3:
  37 +       /* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */
  38 +       pushl   %ecx
  39 +       movl    $MSR_EFER, %ecx
  40 +       rdmsr
  41 +       btsl    $_EFER_LME, %eax
  42 +       wrmsr
  43 +       popl    %ecx
  44 +
  45         /* Enable PAE and LA57 (if required) paging modes */
  46         movl    $X86_CR4_PAE, %eax
  47         cmpl    $0, %edx
  48 diff --git a/arch/x86/boot/compressed/pgtable.h b/arch/x86/boot/compressed/pgtable.h
  49 index 91f75638f6e6..6ff7e81b5628 100644
  50 --- a/arch/x86/boot/compressed/pgtable.h
  51 +++ b/arch/x86/boot/compressed/pgtable.h
  52 @@ -6,7 +6,7 @@
  53  #define TRAMPOLINE_32BIT_PGTABLE_OFFSET        0
  54
  55  #define TRAMPOLINE_32BIT_CODE_OFFSET   PAGE_SIZE
  56 -#define TRAMPOLINE_32BIT_CODE_SIZE     0x60
  57 +#define TRAMPOLINE_32BIT_CODE_SIZE     0x70
  58
  59  #define TRAMPOLINE_32BIT_STACK_END     TRAMPOLINE_32BIT_SIZE
  60
  61 --
  62 2.19.1
  63