Re: Alternate Injection related questions

["Melody (Huibo) Wang" <huibo.wang@amd.com>]

Sorry for re-sending this since I had the wrong mailing list in the previous one. 

On 5/27/2025 10:39 AM, Melody (Huibo) Wang wrote:
> Hi Folks,
> 
> I have a few questions, can you please help?
> 
> I found that when an #HV arrives when interrupts are disabled in the SVSM, the #HV handler will postpone the #HV, but the postponing simply returns.
> 
> Who should re-inject this #HV again?
> 
>     postpone_hv:
>            // HV gets postponed
>            popq    %rcx
>            popq    %rbx
>            popq    %rax
>            addq    $8, %rsp
>            iretq
> 
> Is the hypervisor supposed to re-inject the #HV hoping that interrupts will be enabled?
> 
> How is the hypervisor supposed to know whether a #HV which was postponed, was actually handled so that it doesn't inject it again?
> 
> In SVSM code now, the SVSM will read the doorbell page for extended interrupt information without checking even there is a #HV coming in. Why are we doing this? I think this needs to be triggered by a #HV handler instead of reading the doorbell page automatically. Right?
> 
> I have one more question about gdb tool, "https://coconut-svsm.github.io/svsm/installation/INSTALL/#debugging-using-gdb". I tried to use the tool, but it does not work, I have enabled it :
> 
>  "kernel": {
>        "svsm": {
>            "features": "enable-gdb",
> But not able to make it work. This is the log: 
> 
> $ sudo gdb --ex "target extended-remote /dev/pts/4"
> GNU gdb (Ubuntu 15.0.50.20240403-0ubuntu1) 15.0.50.20240403-git
> Copyright (C) 2024 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
> Type "show copying" and "show warranty" for details.
> This GDB was configured as "x86_64-linux-gnu".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> <https://www.gnu.org/software/gdb/bugs/>.
> Find the GDB manual and other documentation resources online at:
>     <http://www.gnu.org/software/gdb/documentation/>.
> 
> For help, type "help".
> Type "apropos word" to search for commands related to "word".
> Remote debugging using /dev/pts/4
> Ignoring packet error, continuing...
> warning: unrecognized item "timeout" in "qSupported" response
> Ignoring packet error, continuing...
> Ignoring packet error, continuing...
> Remote replied unexpectedly to 'vMustReplyEmpty': timeout
> (gdb) quit
> 
> 
> Thanks,
> Melody
>