After a lot of thinking and browsing in the SVM arch forums I assume now that it shold be fine to enter to paged real mode under SVM guest.
The test case to consider:
(paged) real mode guest -> entering Pmode (not paged) -> disabling the Pmode back
Ths assumption still should be validated with real AMD hardware
Context: AMD's manual about CR0 intercept priority :
"Checks non-memory exceptions (CPL, illegal bit combinations, etc.) before the intercept"
The check for 'paged real mode' suposed to be illegal bit combination ...
Bugfix: VMX: VmEntry should do TPR Virtualization (TPR Shadow + APIC Access Virtualization case is affected) and even could possibly cause TPR Threshold VMEXIT
Minor speedup (of 1-2%) was observed due to new implementation
Remove obsolete dbg_take_irq function and dbg_force_interrupt function from CPU code, the functions were not working properly anyway
fixed enabling of ADX extensions in generic CPUID when enabled through .bochsrc
Small code cleanups on the way to implementation of APIC Registers Virtualization features disclosed in recent Intel SDM rev043
Bochs instruction emulation handlers won't refer to direct fields of instructions like MODRM.NNN or MODRM.RM anymore.
Use generic source/destination indications like SRC1, SRC2 and DST.
All handlers are modified to support new notation. In addition fetchDecode module was modified to assign sources to instructions properly.
Immediate benefits:
- Removal of several duplicated handlers (FMA3 duplicated with FMA4 is a trivial example)
- Simpler to understand fetch-decode code
Future benefits:
- Integration of disassembler into Bochs CPU module, ability to disasm bx_instruction_c instance (planned)
Huge patch. Almost all source files wre modified.
for CPU emulation performance reasons, the alignment check compilation
still can be enabled using configure option --enable-alignment-check.
There is no software in the world which enable #AC exception checking, this
x86 feature is completely legacy but its emulation support costs up to 3-5%
emulation speed.
The checking for #AC exception enable still will be done, if
CPL == 3, EFLAGS.AC = 1 and CR0.AM = 1
but the alignment check is not compiled in, the Bochs will PANIC with corresponding message.
You can press 'always continue' and ignore the PANIC, the simulation will continue as if alignment checking is not enabled.
I am merging the code in order to start making shortcuts between VMX emulation and SVM emulation.
Of course SVM emulation is incomplete, completely untested and not expected to work.
But someone could already take a look one the code and give some suggestions.
Also looking for anybody with existing SVM kernels - as simple as possible - for testing.
Status:
- exceptions intercept is not implemented yet
- IO intercept is not implemented yet
- MSR intercept is not implemented yet
- virtual interrupts are not implemented yet
- CPUID is not implemented yet
No advanced SVM featurez planned - I am implementing the very basic 'Pacifica' document from 2005 using QEMU code as reference.
