Il 05/12/2013 17:12, Laszlo Ersek ha scritto:
> Hi,
>
> I'm working on S3 suspend/resume in OVMF. The problem is that I'm getting an
> unexpected guest reboot for code (LRET) that works on physical hardware. I
> tried to trace the problem with ftrace, but I didn't get any mentions of
> em_ret_far(). (Maybe I was looking in the wrong place.)
What does ftrace say anyway?
> Please find the the assembly-language "trampoline" that is invoked (in 64-bit
> mode) with the 16-bit real mode resume vector placed in "rcx" (EFIAPI calling
> convention). The excerpt is from the edk2 tree,
> "MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/X64/S3Asm.S".
Can you send me a pointer to a git tree or, even better, an OVMF.fd file + instructions
on how to trigger the problem?
> - shared properties:
> Base=0x00000000
> Limit=0xFFFFF
> Type=0xB (C ER A )
> S=0x1 (code/data)
> DPL=0x0
> Present=1
> Avail=0
> LimitGran=0x1 (4KB)
>
> - different properties:
> 0x0010: 0x00CF9B000000FFFF: 64-bitC=0 D/B=1 works
> 0x0028: 0x008F9B000000FFFF: 64-bitC=0 D/B=0 reboots
> 0x0038: 0x00AF9B000000FFFF: 64-bitC=1 D/B=0 works
>
> That is:
> - if I let 64-bit mode execution enabled (64-bitC=1, desc 0x38), the lret
> works.
> - If I switch to compat mode execution (64-bitC=0, desc 0x10), *and* keep the
> default addr/op size 32 bits, the lret still works.
Perhaps you could try switching to 32-bit mode first, then disable paging,
then jump to 16-bit mode. Like this (untested):
diff --git a/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/X64/S3Asm.S b/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/X64/S3Asm.S
index e59fd04..d1cac9d 100644
--- a/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/X64/S3Asm.S
+++ b/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/X64/S3Asm.S
@@ -19,7 +19,7 @@ ASM_PFX(AsmTransferControl):
# rcx S3WakingVector :DWORD
# rdx AcpiLowMemoryBase :DWORD
lea _AsmTransferControl_al_0000(%rip), %eax
- movq $0x2800000000, %r8
+ movq $0x1000000000, %r8
orq %r8, %rax
pushq %rax
shrd $20, %ecx, %ebx
@@ -28,24 +28,32 @@ ASM_PFX(AsmTransferControl):
movl %ebx, jmp_addr(%rip)
lret
_AsmTransferControl_al_0000:
+ # Old SS should still be okay?
+ addl _AsmTransferControl_al_0001-_AsmTransferControl_al_0000, %eax
+ pushl $0x28
+ pushl %eax
+ movq %cr0, %rax
+ movq %cr4, %rbx
+ andl $0x7fffffff, %eax
+ andb $0xdf, %bl
+ movq %rax, %cr0 # sets EFER.LMA=0 too, so says Intel
+ movl $0x0c0000080, %ecx
+ rdmsr
+ andb $0xfe, %ah # set EFER.LME=0
+ wrmsr
+ movq %rbx, %cr4 # only now set CR4.PAE=0
+ lret
+_AsmTransferControl_al_0001:
.byte 0x0b8, 0x30, 0 # mov ax, 30h as selector
movl %eax, %ds
movl %eax, %es
movl %eax, %fs
movl %eax, %gs
movl %eax, %ss
- movq %cr0, %rax
- movq %cr4, %rbx
- .byte 0x66
- andl $0x7ffffffe, %eax
- andb $0xdf, %bl
- movq %rax, %cr0
- .byte 0x66
- movl $0x0c0000080, %ecx
- rdmsr
- andb $0xfe, %ah
- wrmsr
- movq %rbx, %cr4
+ movl %cr0, %rax # Get control register 0
+ .byte 0x66
+ .byte 0x83,0xe0,0xfe # and eax, 0fffffffeh ; Clear PE bit (bit #0)
+ .byte 0xf,0x22,0xc0 # mov cr0, eax ; Activate real mode
> - If I switch to compat mode execution (64-bitC=0, desc 0x28), but also change
> the default addr/op size to 16-bits, then the lret reboots the guest in KVM
> (but works on physical hardware).
Did you try this on physical hardware, or just assumed that? :)
Paolo
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