On 09/04/2019 12:08, Anthony PERARD wrote: > diff --git a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm > b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm > new file mode 100644 > index 0000000000..c4802bf4d1 > --- /dev/null > +++ b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm > @@ -0,0 +1,47 @@ > +;------------------------------------------------------------------------------ > +; @file > +; An entry point use by Xen when a guest is started in PVH mode. > +; > +; Copyright (c) 2019, Citrix Systems, Inc. > +; > +; This program and the accompanying materials are licensed and made available > +; under the terms and conditions of the BSD License which accompanies this > +; distribution. The full text of the license may be found at > +; http://opensource.org/licenses/bsd-license.php > +; > +; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, > WITHOUT > +; WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. > +; > +;------------------------------------------------------------------------------ > + > +BITS 32 > + > +xenPVHMain: > + mov di, 'BP' > + > + ; ESP - Initial value of the EAX register (BIST: Built-in Self Test) > + mov esp, eax
Where is the ABI described? Xen has no BIST, so this will always have the value 0. Stashing it in the stack pointer seems like a weird choice, and a recipe for subtle bugs. > + > + cli Interrupts are guaranteed to be off at this point. > + > + mov ebx, ADDR_OF(gdtr) > + lgdt [ebx] lgdt ADDR_OF(gdtr), presumably? This is 32bit code - there is no need for any indirection through registers for memory operands. > + > + mov eax, SEC_DEFAULT_CR0 > + mov cr0, eax > + > + jmp LINEAR_CODE_SEL:ADDR_OF(.jmpToNewCodeSeg) > +.jmpToNewCodeSeg: > + > + mov eax, SEC_DEFAULT_CR4 > + mov cr4, eax > + > + mov ax, LINEAR_SEL > + mov ds, ax > + mov es, ax > + mov fs, ax > + mov gs, ax > + mov ss, ax > + > + ; return to the Main16 > + OneTimeCallRet TransitionFromReal16To32BitFlat Is there any description of what OneTimeCallRet is, and why a simple jmp wont do? Irrespective of that, you're moving to a function whose name suggests it is in 16bit mode, while you are currently in 32bit flat mode. (SEC_DEFAULT_CR0 has PE set, and LINEAR_SEL is 32bit flat. This clearly isn't correct, but surely we want to skip all the 16bit setup, as well. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
