[BitVisor-users-en:72] Re: Panic on Windows 11

[A.S.]

Dear Mr.Eiraku,

I have run the test to confirm the supposed behaviour without the
hypervisor -
the real hardware generated #GP in this case.

On earlier CPUs the bit CR4.CET was reserved (read as 0),
thus not causing the issue.

I have added check in do_mov_cr and injection of #GP in case of violation.
The issue appears to be fixed.
Sending patch.
Could you please review the change?

--
=============
Best regards,
  Dmitriy

вт, 15 июл. 2025 г. в 04:37, Hideki EIRAKU <hdk at igel.co.jp>:

> Hi,
>
> > RAX 80040033    RCX 80050033    RDX 00000000    RBX 00000001
>
> > CR0 80040033    CR2 FFFFCF8381ADD000    CR3 0032C000    CR4 00B50EF8
>
> The log contains interesting CR0 values.  Only the guest CR0 of CPU8
> is 80040033H while the guest CR0 of others are 80050033.  The
> different bit 16 is WP bit.  The value is also in RAX, so maybe CR0 is
> just set by mov %rax,%cr0 instruction.  Maybe.  I did not know about
> the case that recent operating systems clear WP bit.
>
> Intel(R) 64 and IA-32 Architectures Software Developer's Manual says
> the following check is performed during VM Entry, described in "Checks
> on Guest Control Registers, Debug Registers, and MSRs" section:
>
> > If bit 23 in the CR4 field (corresponding to CET) is 1, bit 16 in the
> CR0 field (WP) must also be 1.
>
> The bit 23 in the guest CR4 value, 00B50EF8, is 1.  Therefore this
> might cause the panic.  BitVisor currently does not handle such case
> correctly.  The Intel manual also says the CR0.CET "must be clear
> before CR0.WP can be cleared" so the guest behavior looks illegal, but
> VMM needs to do something for such illegal case i.e. generating
> general protection exception, ignoring the modification, etc. like a
> real processor.
>
> --
> Hideki EIRAKU <hdk at igel.co.jp>
>
> From: "A.S." <an4smith at gmail.com>
> Subject: [BitVisor-users-en:70] Panic on Windows 11
> Date: Tue, 15 Jul 2025 01:07:55 +0300
>
> > Hi,
> >
> > I experience Bitvisor panic when trying to startup Windows 11 after
> loading
> > Bitvisor.
> > Platform: 12th Gen CPU, Chipset: Q670
> > Older hardware and older OS runs fine.
> > Logs with panic in attachment.
> > Could you please help diagnose and possibly fix the problem?
> >
> > --
> > =========
> > Best Regards,
> >   Dmitriy
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