Cc other reviewers. Reviewed-by: Eric Dong <eric.d...@intel.com>
Thanks, Eric > -----Original Message----- > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of John E > Lofgren > Sent: Tuesday, September 10, 2019 2:41 AM > To: devel@edk2.groups.io > Subject: [edk2-devel] [Patch V2] UefiCpuPkg/CpuExceptionHandlerLib: Fix > #AC split lock > > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2150 > > V2 changes: > Add xchg 16 bit instructions to handle sgdt and sidt base > 63:48 bits and 47:32 bits. > Add comment to explain why xchg 64bit isnt being used > > Fix #AC split lock's caused by seperating base and limit from sgdt and sidt by > changing xchg operands to 32-bit to stop from crossing cacheline. > > Signed-off-by: John E Lofgren <john.e.lofg...@intel.com> > --- > > UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nas > m | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) > > diff --git > a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n > asm > b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n > asm > index 4db1a09f28..7b7642b290 100644 > --- > a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n > asm > +++ > b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm. > +++ nasm > @@ -180,21 +180,29 @@ HasErrorCode: > push qword [rbp + 24] > > ;; UINT64 Gdtr[2], Idtr[2]; > + ; sidt and sgdt saves 10 bytes to memory, 8 bytes = base and 2 bytes = > limit. > + ; To avoid #AC split lock when separating base and limit into their > + ; own separate 64 bit memory, we can’t use 64 bit xchg since base > [63:48] bits > + ; may cross the cache line. > xor rax, rax > push rax > push rax > sidt [rsp] > - xchg rax, [rsp + 2] > - xchg rax, [rsp] > - xchg rax, [rsp + 8] > + xchg eax, [rsp + 2] > + xchg eax, [rsp] > + xchg eax, [rsp + 8] > + xchg ax, [rsp + 6] > + xchg ax, [rsp + 4] > > xor rax, rax > push rax > push rax > sgdt [rsp] > - xchg rax, [rsp + 2] > - xchg rax, [rsp] > - xchg rax, [rsp + 8] > + xchg eax, [rsp + 2] > + xchg eax, [rsp] > + xchg eax, [rsp + 8] > + xchg ax, [rsp + 6] > + xchg ax, [rsp + 4] > > ;; UINT64 Ldtr, Tr; > xor rax, rax > -- > 2.16.2.windows.1 > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#47182): https://edk2.groups.io/g/devel/message/47182 Mute This Topic: https://groups.io/mt/34083544/21656 Mute #ac: https://groups.io/mk?hashtag=ac&subid=3846945 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
