Re: [9front] kernel crash in bhyve

[Nick Owens <mischief@offblast.org>]

you cannot just read #P/msr at offset 0. the offset is significant. io
-M can be used to read an MSR at a specific offset.

On Thu, Dec 10, 2020 at 12:37 PM Xiao-Yong Jin <meta.jxy@gmail.com> wrote:
>
> > On Dec 10, 2020, at 5:30 AM, cinap_lenrek@felloff.net wrote:
> >
> > Btw, would it be possible for you to file a bug
> > with bhyve?
> >
> > I do not have a bsd installation nor do i want to
> > subscribe to their mailinglist right now.
> >
> > The issue is that the mtrr values they give us
> > are basically useless.
> >
> > Qemu, vmware and everyone else gets this right.
> >
> > The simplest fix might be that they just change
> > cpuid to tell the guest that mtrr is not supported.
> >
> > --
> > cinap
>
> I'm not sure I understand the issue completely.
>
> I was using a specific debug switch '-w' in bhyve.
>
>                  -w          Ignore accesses to unimplemented Model Specific
>                              Registers (MSRs).  This is intended for debug
>                              purposes.
>
> Because previously, 9front wouldn't boot without this flag.
> Now I guess you added more error checking during the boot,
> and 9front boots fine without this '-w'.  However, without
> this '-w' to bhyve, the MTRR code you gave me produces an
> error,
>
> rdmsr to register 0xc0010010 on vcpu 0
>                                       rdmsr c0010010: bad arg in system call
> range                0       1000000000 (      1000000000) uc
> cache 0x0000000000000000     68719476736 uc
>
> It looks like '#P/msr' just cannot be read.
>
> ; cat '#P/msr'
> cat: error reading #P/msr: bad arg in system call
>