RE: [edk2] apparent KVM problem with LRET in TianoCore S3 resume trampoline

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Hi Paolo
Do you mean the OVEM already transfer control to OS Waking vector?
System stuck just because the page table in 0x9C000 is corrupt?

Thank you
Yao Jiewen

-----Original Message-----
From: Paolo Bonzini [mailto:pbonzini@xxxxxxxxxx] 
Sent: Friday, December 06, 2013 8:03 PM
To: edk2-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: KVM devel mailing list
Subject: Re: [edk2] apparent KVM problem with LRET in TianoCore S3 resume trampoline

Il 05/12/2013 19:29, Laszlo Ersek ha scritto:
> On 12/05/13 18:42, Paolo Bonzini wrote:
>> 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?
> 
> (pls. see in the next msg I sent)

Actually I meant the ftrace without any patches.

Thanks to your binary I now reproduced the issue and it looks like the
64-bit->16-bit switch works:

 qemu-system-x86-4081  [001] 62650.335040: kvm_exit:             reason CR_ACCESS rip 0x3cf7ae45 info 0 0
 qemu-system-x86-4081  [001] 62650.335041: kvm_cr:               cr_write 0 = 0x32
 qemu-system-x86-4081  [001] 62650.335046: kvm_entry:            vcpu 0

	This is the "mov %rax, %cr0". PE and PG are turned off.

 qemu-system-x86-4081  [001] 62650.335047: kvm_exit:             reason MSR_READ rip 0x3cf7ae4e info 0 0
 qemu-system-x86-4081  [001] 62650.335048: kvm_msr:              msr_read c0000080 = 0x100
 qemu-system-x86-4081  [001] 62650.335048: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335048: kvm_exit:             reason MSR_WRITE rip 0x3cf7ae53 info 0 0
 qemu-system-x86-4081  [001] 62650.335049: kvm_msr:              msr_write c0000080 = 0x0
 qemu-system-x86-4081  [001] 62650.335050: kvm_entry:            vcpu 0

	LME is turned off.

 qemu-system-x86-4081  [001] 62650.335050: kvm_exit:             reason CR_ACCESS rip 0x3cf7ae55 info 304 0
 qemu-system-x86-4081  [001] 62650.335050: kvm_cr:               cr_write 4 = 0x640
 qemu-system-x86-4081  [001] 62650.335053: kvm_entry:            vcpu 0

	PAE is turned off.

 qemu-system-x86-4081  [001] 62650.335054: kvm_exit:             reason CR_ACCESS rip 0x11e6 info 0 0
 qemu-system-x86-4081  [001] 62650.335054: kvm_cr:               cr_write 0 = 0x33
 qemu-system-x86-4081  [001] 62650.335054: kvm_entry:            vcpu 0

	Here we're already in real mode.  The weird RIP is explained by
	the first few bytes after the FACS resume vector:

		0x9a1d:0000:  cli    
		0x9a1d:0001:  cld    
		0x9a1d:0002:  ljmp   $9900,$11d7

	9900:11d7 is the same physical address as 9a1d:0007.  Fast forward a bit:

 qemu-system-x86-4081  [001] 62650.335071: kvm_exit:             reason CR_ACCESS rip 0x9aec7 info 0 0
 qemu-system-x86-4081  [001] 62650.335071: kvm_cr:               cr_write 0 = 0x80010001
 qemu-system-x86-4081  [001] 62650.335074: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335076: kvm_exit:             reason TRIPLE_FAULT rip 0x0 info 0 0

Disassembling mixed 16-/32-/64-bit is a pain, so I ran QEMU with -no-shutdown -no-reboot and dumped the memory with

	(qemu) dump-guest-memory tramp.dmp 0x90000 0x10000

Lets look at the rest of the trace now.  After the previous cr0 access we have:

 qemu-system-x86-4081  [001] 62650.335055: kvm_exit:             reason CR_ACCESS rip 0x11fa info 0 0
 qemu-system-x86-4081  [001] 62650.335055: kvm_cr:               cr_write 0 = 0x32
 qemu-system-x86-4081  [001] 62650.335055: kvm_entry:            vcpu 0

	It gets out to real mode again.  No idea why.  It does some setup.

 qemu-system-x86-4081  [001] 62650.335056: kvm_exit:             reason MSR_WRITE rip 0x1258 info 0 0
 qemu-system-x86-4081  [001] 62650.335056: kvm_msr:              msr_write 1a0 = 0x1
 qemu-system-x86-4081  [001] 62650.335057: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335057: kvm_exit:             reason WBINVD rip 0x1001 info 0 0
 qemu-system-x86-4081  [001] 62650.335057: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335058: kvm_exit:             reason CPUID rip 0x1073 info 0 0
 qemu-system-x86-4081  [001] 62650.335058: kvm_cpuid:            func 0 rax 4 rbx 756e6547 rcx 6c65746e rdx 49656e69
 qemu-system-x86-4081  [001] 62650.335059: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335059: kvm_exit:             reason CPUID rip 0x10c0 info 0 0
 qemu-system-x86-4081  [001] 62650.335059: kvm_cpuid:            func 1 rax 663 rbx 800 rcx 80802001 rdx 78bfbfd
 qemu-system-x86-4081  [001] 62650.335059: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335060: kvm_exit:             reason CPUID rip 0x10ff info 0 0
 qemu-system-x86-4081  [001] 62650.335060: kvm_cpuid:            func 1 rax 663 rbx 800 rcx 80802001 rdx 78bfbfd
 qemu-system-x86-4081  [001] 62650.335060: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335061: kvm_exit:             reason CPUID rip 0x1117 info 0 0
 qemu-system-x86-4081  [001] 62650.335061: kvm_cpuid:            func 80000000 rax 8000000a rbx 756e6547 rcx 6c65746e rdx 49656e69
 qemu-system-x86-4081  [001] 62650.335061: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335062: kvm_exit:             reason CPUID rip 0x1127 info 0 0
 qemu-system-x86-4081  [001] 62650.335062: kvm_cpuid:            func 80000001 rax 663 rbx 0 rcx 1 rdx 2191abfd
 qemu-system-x86-4081  [001] 62650.335062: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335063: kvm_exit:             reason CPUID rip 0x113f info 0 0
 qemu-system-x86-4081  [001] 62650.335063: kvm_cpuid:            func 1 rax 663 rbx 800 rcx 80802001 rdx 78bfbfd
 qemu-system-x86-4081  [001] 62650.335063: kvm_entry:            vcpu 0
 qemu-system-x86-4081  [001] 62650.335064: kvm_exit:             reason CR_ACCESS rip 0x103c info 0 0
 qemu-system-x86-4081  [001] 62650.335064: kvm_cr:               cr_write 0 = 0x1
 qemu-system-x86-4081  [001] 62650.335064: kvm_entry:            vcpu 0

	Enabling protected mode:

	0009A036  66B801000000      mov eax,0x1
	0009A03C  0F22C0            mov cr0,eax
	0009A03F  66EA90AE09000800  jmp dword 0x8:0x9ae90

	This is a 32-bit selector.

	0009AE90  8ED2              mov ss,edx
	0009AE92  81C400900900      add esp,0x99000
	0009AE98  8EDA              mov ds,edx
	0009AE9A  8EC2              mov es,edx
	0009AE9C  8EE2              mov fs,edx
	0009AE9E  8EEA              mov gs,edx

 qemu-system-x86-4081  [001] 62650.335065: kvm_exit:             reason CR_ACCESS rip 0x9aea5 info 4 0
 qemu-system-x86-4081  [001] 62650.335065: kvm_cr:               cr_write 4 = 0x6f0
 qemu-system-x86-4081  [001] 62650.335066: kvm_entry:            vcpu 0

	Enabling PAE:

	0009AEA0  A110D00900        mov eax,[0x9d010]
	0009AEA5  0F22E0            mov cr4,eax

 qemu-system-x86-4081  [001] 62650.335067: kvm_exit:             reason CR_ACCESS rip 0x9aead info 3 0
 qemu-system-x86-4081  [001] 62650.335067: kvm_cr:               cr_write 3 = 0x9c000
 qemu-system-x86-4081  [001] 62650.335068: kvm_entry:            vcpu 0

	Setting CR3

	0009AEA8  B800C00900        mov eax,0x9c000
	0009AEAD  0F22D8            mov cr3,eax

 qemu-system-x86-4081  [001] 62650.335068: kvm_exit:             reason MSR_WRITE rip 0x9aec0 info 0 0
 qemu-system-x86-4081  [001] 62650.335070: kvm_msr:              msr_write c0000080 = 0x901
 qemu-system-x86-4081  [001] 62650.335070: kvm_entry:            vcpu 0

	Enabling LME

	0009AEB0  A108D00900        mov eax,[0x9d008]
	0009AEB5  8B150CD00900      mov edx,[dword 0x9d00c]
	0009AEBB  B9800000C0        mov ecx,0xc0000080
	0009AEC0  0F30              wrmsr

 qemu-system-x86-4081  [001] 62650.335071: kvm_exit:             reason CR_ACCESS rip 0x9aec7 info 0 0
 qemu-system-x86-4081  [001] 62650.335071: kvm_cr:               cr_write 0 = 0x80010001
 qemu-system-x86-4081  [001] 62650.335074: kvm_entry:            vcpu 0

	Enabling paging

	0009AEC2  B801000180        mov eax,0x80010001
	0009AEC7  0F22C0            mov cr0,eax

	But before we get here:

	0009AECA  EA30AF09001000    jmp dword 0x10:0x9af30

	... kaboom:

 qemu-system-x86-4081  [001] 62650.335076: kvm_exit:             reason TRIPLE_FAULT rip 0x0 info 0 0

The page tables are, ahem, crap:

000c000: 6750 fe01 0000 0000 0000 0000 0000 0000  gP..............
000c010: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c020: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c030: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c040: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c050: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c060: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c070: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c080: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c090: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c0a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c0b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c0c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c0d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c0e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000c0f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................

This is 0x9c000.  Strikes any bell?

Paolo

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