On Sun, Jun 09, 2013 at 11:23:26PM +0800, 李春奇 <Arthur Chunqi Li> wrote: > On Sun, Jun 9, 2013 at 10:09 PM, Gleb Natapov <gleb@xxxxxxxxxx> wrote: > > On Sun, Jun 09, 2013 at 09:22:27PM +0800, 李春奇 <Arthur Chunqi Li> wrote: > >> On Sun, Jun 9, 2013 at 8:49 PM, Gleb Natapov <gleb@xxxxxxxxxx> wrote: > >> > On Sun, Jun 09, 2013 at 08:44:32PM +0800, 李春奇 <Arthur Chunqi Li> wrote: > >> >> On Sun, Jun 9, 2013 at 7:07 PM, Gleb Natapov <gleb@xxxxxxxxxx> wrote: > >> >> > On Fri, Jun 07, 2013 at 10:31:38AM +0800, Arthur Chunqi Li wrote: > >> >> >> Add a function trap_emulator to run an instruction in emulator. > >> >> >> Set inregs first (%rax, %rsp, %rbp, %rflags have special usage and > >> >> >> cannot set in inregs), put instruction codec in alt_insn and call > >> >> >> func with alt_insn_length. Get results in outregs. > >> >> >> > >> >> > Why %rax, %rsp, %rbp, %rflags cannot be set in inregs? > >> >> > > >> >> > %rax because trapping instruction uses it? Use one that does not use > >> >> > register at all: MOV r/m32, imm32 > >> >> I don't know why set %rax before call alt_insn_page can cause error. I > >> >> use "xchg %%rax, 0+%[save]" before "call *%1" and the %rcx is not set > >> >> correctly. > >> > We better find this out :) > >> I found that before calling alt_insn_page, address of "mem" is saved > >> to %rax, why? > > Because instruction that we use to trigger vmexit is mov %eax, (%rax) so > > MMOI address mem is loaded into %rax before jumping into it. > I think this is why changing %rax will cause error. If we use mov > %eax, (%rax) to trigger vmexit, and %rax is changed before calling > alt_insn_page, codes in alt_insn_page will not be executed and return > directly. > I changed the codes which trigger vmexit to "mov %eax, (%r8)" and set > "mem" to %r8 before calling alt_insn_page, it runs OK. > Just use an instruction that does not use registers at all. mov $1, addr where addr is immediate and encoded from mem parameter. > Besides, I also don't know if changed %rflags may cause some > unpredictable actions, so now we just treat it with no error :) If test sets rflags to a value that causes crashes this is a test bug, no need to prevent this from happening. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
