Re: QEMU on x64

[Paolo Bonzini]

On 30/07/21 19:36, Christopher Caulfield wrote:
> Hi QEMU community,
>
> This is Christopher from the debugging experiences team at Microsoft 
> focused on kernel debugging. I am reaching out with a few questions 
> about QEMU on x64.
>
>  1. Is it possible for the QEMU-x86-64 GDB Server to send the full set
>     of x64 system registers (whether they are included in a separated
>     system xml file or as part of the core registers xml file)?
>       * e.g. System registers missing from i386-64bit.xml file
>
>         DWORD64 IDTBase;
>         DWORD64 IDTLimit;
>         DWORD64 GDTBase;
>         DWORD64 GDTLimit;
>         DWORD SelLDT;
>         SEG64_DESC_INFO SegLDT;
>         DWORD SelTSS;
>         SEG64_DESC_INFO SegTSS;

Yes, that is possible.

>  2. How can I access x64 MSR registers by using the QEMU-x86-64 GDB server?
>       * #define MSR_EFER 0xc0000080 // extended function enable register
>         #define MSR_STAR 0xc0000081 // system call selectors
>         #define MSR_LSTAR 0xc0000082 // system call 64-bit entry
>         #define MSR_CSTAR 0xc0000083 // system call 32-bit entry
>  3. Going off of #2 - can you access it via reading GDB memory command?
>     if not - is there any plan to support reading/writing to MSRs via
>     QEMU-x86-64 GDB server?

Right now it's not possible, but for specific MSRs it's possible to add 
them to the XML and export them.

Can you create an issue on https://gitlab.com/qemu-project/qemu/-/issues 
please?

Paolo