[svsm-devel] Launch coconut-svsm using IGVM

[Claudio Siqueira de Carvalho]

On Thu, 2024-03-28 at 11:54 -0500, Tom Lendacky wrote:
> On 3/27/24 16:49, Tom Lendacky wrote:
> > On 2/9/24 09:51, Jörg Rödel wrote:
> > > Hi Claudio,
> > > 
> > > On Fri, Feb 09, 2024 at 02:46:03PM +0000, Claudio Siqueira de Carvalho 
> > > wrote:
> > > > I was doing some research on IGVM, but I did not find any example. Does 
> > > > anybody
> > > > have an example of an IGVM file and a QEMU command line that I could 
> > > > use to
> > > > launch the coconut-svsm?
> > > > 
> > > > This might be helpful for other people too.
> > > 
> > > The COCONUT build process will generate two IGVM files, one for use with
> > > QEMU and one for use with Hyper-V.
> > > 
> > > To use it with QEMU, you need an IGVM-enabled QEMU, instructions on how
> > > to get one can be found in here:
> > > 
> > >     
> > > https://github.com/roy-hopkins/svsm/blob/igvm_install_doc/Documentation/IN
> > > STALL.md
> > > 
> > > This is a file from Roy's pending PR on updating the documentation for
> > > the IGVM switch.
> > 
> > I just tried building everything fresh on a new system based on the 
> > installation instructions and can't get the firmware to launch. Doing some 
> > debugging, the firmware loading appears to be off by a page (0x1000). In 
> > other words, the code that should be at the CS:RIP 0xfffffff0 is actually 
> > located at 0xffffeff0, with all 0's at 0xfffffff0.
> > 
> > I don't have a full grasp on the Qemu IGVM support to understand if it is 
> > the IGVM file that is built wrong or the Qemu IGVM support that ends up 
> > off by a page. It appears that the firmware is handled as the last item in 
> > igvm_process() and if process_mem_page() is invoked with "i - 1" instead 
> > of "i", then the firmware begins booting.
> 
> Just to supply a bit more info, the failing launch ends with the following:
> 
> ...
> [SVSM] Launching Firmware
> [SVSM] Launching request-processing task on CPU 0
> qemu-system-x86_64: warning: memory fault: GPA 0x0 size 0x1000 flags 0x8
> qemu-system-x86_64: cpus are not resettable, terminating
> 
> 
> The following patch to Qemu works around the issue, but I'm unsure if this 
> is a proper fix. The error can either be in Qemu or the IGVM creation process.

I am also having the same problem. If I bisected it right, the problem seems to
be in the igvmbuilder.

https://github.com/coconut-svsm/svsm/issues/311

Thanks,
Claudio

> 
> diff --git a/backends/igvm.c b/backends/igvm.c
> index df663b300b..1923d31ad6 100644
> --- a/backends/igvm.c
> +++ b/backends/igvm.c
> @@ -675,7 +675,7 @@ void igvm_process(ConfidentialGuestSupport *cgs)
>        * to reduce the number of memory regions we create. Make sure the 
> last group is
>        * processed with this call.
>        */
> -    process_mem_page(cgs, i, NULL);
> +    process_mem_page(cgs, i - 1, NULL);
> 
>       QTAILQ_FOREACH(parameter, &parameter_data, next)
>       {
> 
> Thanks,
> Tom
> 
> > 
> > Thanks,
> > Tom
> > 
> > > 
> > > Hope that helps.
> > > 
> > > Regards,
> > > 
> > >     Joerg