https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #31 from Jidong Xiao jidong.x...@gmail.com ---
Hi, Paolo,
I added a sti instruction in kvm-unit-tests:x86/debug.c, like this:
asm volatile(
pushf\n\t
pop %%rax\n\t
sti\n\t
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #32 from Jatin Kumar jatin.iitde...@gmail.com ---
(In reply to Jidong Xiao from comment #29)
Okay, I will try the sti instruction.
Jatin, since your title says that there is something wrong with the sti
instruction, but looking at
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #33 from Jidong Xiao jidong.x...@gmail.com ---
Jatin, thanks for the clarification. Are you using kgdb to perform single step
kernel code? I am still wondering how did you do the single step execution for
kernel level code.
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https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #34 from Jatin Kumar jatin.iitde...@gmail.com ---
(In reply to Jidong Xiao from comment #33)
Jatin, thanks for the clarification. Are you using kgdb to perform single
step kernel code? I am still wondering how did you do the single
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #25 from Jidong Xiao jidong.x...@gmail.com ---
(In reply to Jatin Kumar from comment #24)
linux:~/code/cvedr # ./accessmsr
Segmentation fault
You got a seg fault because it is privileged instruction and I run it in
kernel mode
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #26 from Jatin Kumar jatin.iitde...@gmail.com ---
In arch/x86/kvm/vmx.c file, there is a complete list of kvm_vmx_exit_handlers,
you can find there appropriate handlers for each of the exit reasons. There is
a handle_io() handler. Can
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #27 from Jidong Xiao jidong.x...@gmail.com ---
Jatin, after I have added printk in handle_io, it looks like the printk will be
called very frequently, I don't need to run any own program in the guest OS,
the printk message in
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #28 from Paolo Bonzini bonz...@gnu.org ---
As Jatin said, most of the time the emulator is not invoked for instructions
that require intervention of the hypervisor. Instead, the processor provides
enough pre-decoded information about
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #29 from Jidong Xiao jidong.x...@gmail.com ---
Okay, I will try the sti instruction.
Jatin, since your title says that there is something wrong with the sti
instruction, but looking at your sample code, it does not include a sti
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #18 from Jidong Xiao jidong.x...@gmail.com ---
Hi, Paolo,
I am still reading the source code so as to understand the root cause of this
problem. In particular, I added some printk statements in x86_emulate_insn().
For example, I added
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #19 from Jatin Kumar jatin.iitde...@gmail.com ---
I am not sure if I am correct but `add` doesn't look like any privileged or
special instruction so if running with KVM it should run directly on the
hardware and without needing
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #20 from Jidong Xiao jidong.x...@gmail.com ---
Thanks Jatin, I actually tried some other instructions, like accessing cr
register. I use the following program:
linux:~/code/cvedr # cat getcr.c
#include stdio.h
main(){
asm
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #21 from Jatin Kumar jatin.iitde...@gmail.com ---
The way I would approach this problem is to first check if there is a VM_EXIT
while executing this instruction. You should be able to find that in
vmx_vcpu_run() function (I guess in
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #22 from Jidong Xiao jidong.x...@gmail.com ---
Alright, I added a printk statement in the wrmsr case, like this:
case 0x30:
printk(KERN_ERR DEBUG: Passed %s %d
\n,__FUNCTION__,__LINE__);
/*
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #23 from Jidong Xiao jidong.x...@gmail.com ---
Jatin, do you mean that if one instruction triggers a VM_EXIT, then it won't
trigger the emulate code? So why the emulate code tries to emulate those
privileged instructions, like wrmsr,
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #24 from Jatin Kumar jatin.iitde...@gmail.com ---
linux:~/code/cvedr # ./accessmsr
Segmentation fault
You got a seg fault because it is privileged instruction and I run it in kernel
mode not user mode. But you are likely to be
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #7 from Paolo Bonzini bonz...@gnu.org ---
Hi Jidong, no this is not fixed yet. Basically OUT instructions are emulated
by KVM, and support for single-stepping and breakpoints in the emulator is
quite minimal.
3.12 added some support
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #8 from Jidong Xiao jidong.x...@gmail.com ---
Hi, Jatin,
from inside the OS means from within the Guest OS right?
(In reply to Jatin Kumar from comment #5)
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--- Comment #9 from Jidong Xiao jidong.x...@gmail.com ---
Hi, Paolo,
It seems that Gleb's patch
commit 03617c188f41eeeb4223c919ee7e66e5a114f2c6
KVM: VMX: mark unusable segment as nonpresent
fixed a similar problem like this, look at this:
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #10 from Paolo Bonzini bonz...@gnu.org ---
No, hardware error 0x8021 includes pretty much everything that could go
wrong in vmx.c. :)
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--- Comment #11 from Jidong Xiao jidong.x...@gmail.com ---
Hi, Paolo, thanks for your explanation. I am interested in fixing this. So
what's the technical challenge here?
When you say support for single-stepping and breakpoints in the emulator is
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #12 from Paolo Bonzini bonz...@gnu.org ---
Hi, Paolo, thanks for your explanation. I am interested in fixing this. So
what's the technical challenge here?
The first step is to reproduce the failure. To do this you can make a
patch
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--- Comment #13 from Jidong Xiao jidong.x...@gmail.com ---
Great, I will try. Yes I have the inter manual and I have studied it for a
while, so basically I know the data structure of VMCS. To reproduce the
failure, so, if I use gdb in a guest OS,
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--- Comment #14 from Jatin Kumar jatin.iitde...@gmail.com ---
(In reply to Jidong Xiao from comment #8)
Hi, Jatin,
from inside the OS means from within the Guest OS right?
(In reply to Jatin Kumar from comment #5)
Hello Jidong,
Yes it means
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--- Comment #15 from Paolo Bonzini bonz...@gnu.org ---
if I use gdb in a guest OS, like to debug a program inside the Guest OS, and
run the single step command in gdb, that should trigger this bug right
Yes. For kvm-unit-tests you would
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #16 from Jidong Xiao jidong.x...@gmail.com ---
Alright, thank you Paolo, I will try and let you know once I am done.(In reply
to Paolo Bonzini from comment #15)
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--- Comment #17 from Jidong Xiao jidong.x...@gmail.com ---
Hi,Paolo,
I am not familiar with kvm-unit-tests, and I cannot find any documents describe
it. So I use gdb to debug.
And yes I can reproduce the problem. I just use Jatin's sample code
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #2 from Jatin Kumar jatin.iitde...@gmail.com ---
Hello Jidong, thanks for the info. I will try and let you know.
While you are at this, can you please help me another single stepping issue and
the issue is:
1. While single stepping,
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--- Comment #4 from Jidong Xiao jidong.x...@gmail.com ---
Jatin, are you using gdb to do the single step?(In reply to Jatin Kumar from
comment #2)
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--- Comment #5 from Jatin Kumar jatin.iitde...@gmail.com ---
@Paolo: Thanks for the info. That makes sense to me.
(In reply to Jidong Xiao from comment #4)
Jatin, are you using gdb to do the single step?(In reply to Jatin Kumar from
comment #2)
https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #6 from Jatin Kumar jatin.iitde...@gmail.com ---
(In reply to Jatin Kumar from comment #5)
whenever I hit an out instruction, the very next instruction is not skipped
Sorry I meant 'is skipped'.
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