Reviewed-by: Eric Dong eric.dong@intel.com Pushed: SHA-1: 00b8bf7eda00fb6f0197d3968b6078cfdb4870fa * UefiCpuPkg/SecCore: Add pre-memory AP vector REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2776 Thanks, Eric From: Ni, Ray Sent: Tuesday, June 23, 2020 8:57 AM To: Cole, Deric ; devel@edk2.groups.io Cc: Dong, Eric ; Laszlo Ersek Subject: RE: [PATCH] UefiCpuPkg/SecCore: Add pre-memory AP vector Reviewed-by: Ray Ni > > -----Original Message----- > From: Cole, Deric > > Sent: Wednesday, June 3, 2020 12:42 AM > To: Ni, Ray >; devel@edk2.groups.io > Cc: Dong, Eric >; Laszlo Ersek > > Subject: RE: [PATCH] UefiCpuPkg/SecCore: Add pre-memory AP vector > > Ray, > > The NOP is not a functional change, it's just for ease of debug. > > Before, this file was padding with zeros in various places. When viewing this memory using a disassembler, two > subsequent zero-bytes show up as an ADD instruction, which I found confusing. But worse, if the number of zero-bytes was > odd, the disassembler might try to "consume" part of the next (real) instruction as an operand to the last hypothetical > ADD. > > Since NOP is a 1-byte instruction, I used that instead, so it is easier to visually identify the real code versus the padding > when viewing disassembly. > > -Deric > > -----Original Message----- > From: Ni, Ray > > Sent: Monday, June 1, 2020 9:51 PM > To: Cole, Deric >; devel@edk2.groups.io > Cc: Dong, Eric >; Laszlo Ersek > > Subject: RE: [PATCH] UefiCpuPkg/SecCore: Add pre-memory AP vector > > Deric, > Can you explain why changing all padding 0x0 to 0x90 (nop) in your patch? > > Is it required to enable AP start up in pre-mem? > > Thanks, > Ray > > > -----Original Message----- > > From: Cole, Deric > > > Sent: Tuesday, June 2, 2020 6:32 AM > > To: devel@edk2.groups.io > > Cc: Cole, Deric >; Dong, Eric > > >; Ni, Ray >; Laszlo Ersek > > > > > Subject: [PATCH] UefiCpuPkg/SecCore: Add pre-memory AP vector > > > > REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2776 > > > > Add a vector at 0xFF000 (0xFFFFF000) that can be used by > > Init-SIPI-SIPI to start an AP before memory is initialized. This > > vector jumps into the same SEC entry point as the ordinary reset > > vector, with a special value of "AP" in the DI register. The > > platform-specific SEC code is expected to check for that value and > > take a different path for APs, if this feature is supported by the platform. > > > > Cc: Eric Dong > > > Cc: Ray Ni > > > Cc: Laszlo Ersek > > > Signed-off-by: Deric Cole > > > --- > > UefiCpuPkg/SecCore/Ia32/ResetVec.nasmb | 31 > > ++++++++++++++++++++++++------- > > 1 file changed, 24 insertions(+), 7 deletions(-) > > > > diff --git a/UefiCpuPkg/SecCore/Ia32/ResetVec.nasmb > > b/UefiCpuPkg/SecCore/Ia32/ResetVec.nasmb > > index f41b9669d0..1dfc4efe4c 100644 > > --- a/UefiCpuPkg/SecCore/Ia32/ResetVec.nasmb > > +++ b/UefiCpuPkg/SecCore/Ia32/ResetVec.nasmb > > @@ -10,7 +10,7 @@ > > ; Abstract: > > > > ; > > > > ; Reset Vector Data structure > > > > -; This structure is located at 0xFFFFFFC0 > > > > +; This structure is located at 0xFFFFF000 > > > > ; > > > > > > ;--------------------------------------------------------------------- > > --------- > > > > > > > > @@ -23,19 +23,36 @@ USE16 > > ; > > > > > > > > ORG 0h > > > > + > > > > +; > > > > +; 0xFFFFF000 > > > > +; > > > > +; We enter here with CS:IP = 0xFF00:0x0000. Do a far-jump to change > > +CS to > > 0xF000 > > > > +; and IP to ApStartup. > > > > +; > > > > +ApVector: > > > > + mov di, "AP" > > > > + jmp 0xF000:0xF000+ApStartup > > > > + > > > > + TIMES 0xFC0-($-$$) nop > > > > + > > > > +; > > > > +; This should be at 0xFFFFFFC0 > > > > +; > > > > + > > > > ; > > > > ; Reserved > > > > ; > > > > ReservedData: DD 0eeeeeeeeh, 0eeeeeeeeh > > > > > > > > - TIMES 0x10-($-$$) DB 0 > > > > + TIMES 0xFD0-($-$$) nop > > > > ; > > > > -; This is located at 0xFFFFFFD0h > > > > +; This is located at 0xFFFFFFD0 > > > > ; > > > > mov di, "PA" > > > > jmp ApStartup > > > > > > > > - TIMES 0x20-($-$$) DB 0 > > > > + TIMES 0xFE0-($-$$) nop > > > > ; > > > > ; Pointer to the entry point of the PEI core > > > > ; It is located at 0xFFFFFFE0, and is fixed up by some build tool > > > > @@ -53,7 +70,7 @@ ASM_PFX(InterruptHandler): > > jmp $ > > > > iret > > > > > > > > - TIMES 0x30-($-$$) DB 0 > > > > + TIMES 0xFF0-($-$$) nop > > > > ; > > > > ; For IA32, the reset vector must be at 0xFFFFFFF0, i.e., 4G-16 byte > > > > ; Execution starts here upon power-on/platform-reset. > > > > @@ -74,7 +91,7 @@ ApStartup: > > DW -3 > > > > > > > > > > > > - TIMES 0x38-($-$$) DB 0 > > > > + TIMES 0xFF8-($-$$) nop > > > > ; > > > > ; Ap reset vector segment address is at 0xFFFFFFF8 > > > > ; This will be fixed up by some build tool, > > > > @@ -83,7 +100,7 @@ ApStartup: > > ; > > > > ApSegAddress: dd 12345678h > > > > > > > > - TIMES 0x3c-($-$$) DB 0 > > > > + TIMES 0xFFC-($-$$) nop > > > > ; > > > > ; BFV Base is at 0xFFFFFFFC > > > > ; This will be fixed up by some build tool, > > > > -- > > 2.26.2.windows.1 > >