Re: [XTF PATCH] x86: Remove Xen as a hard requirement to run XTF.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/09/2025 9:54 am, Alejandro Vallejo wrote:
> If Xen isn't detected on CPUID, then:
>
>  * Skip setting up Xenbus/PV-console/shared_info/hypercalls/qemu-debug.
>  * Register COM1 as an output callback.
>
> This patch enables running XTF on QEMU-TCG/KVM out of the box.

When I did a KVM branch for amluto,
https://xenbits.xen.org/gitweb/?p=people/andrewcoop/xen-test-framework.git;a=shortlog;h=refs/heads/kvm
was what was necessary to get tests to pass.

I can see the need for MB1 going away now that KVM uses the PVH
entrypoint, but is the rest really unnecessary?

> diff --git a/arch/x86/setup.c b/arch/x86/setup.c
> index 2ac212e..6172c7e 100644
> --- a/arch/x86/setup.c
> +++ b/arch/x86/setup.c
> @@ -243,11 +245,19 @@ static void map_shared_info(void)
>          panic("Failed to map shared_info: %d\n", rc);
>  }
>  
> +static void pio_write(uint16_t port, const char *buf, size_t len)
> +{
> +    asm volatile("rep; outsb" : "+S" (buf), "+c" (len) : "d" (port));
> +}

I've factored out rep_movsb() in the proper place for library functions,
and without the rebasing issue reinserting the erroneous ;.

> @@ -255,12 +265,41 @@ static void xen_console_write(const char *buf, size_t 
> len)
>      hypercall_console_write(buf, len);
>  }
>  
> +static bool detect_xen_runtime(void)
> +{
> +    uint32_t eax, ebx, ecx, edx;
> +
> +    /* PV tests always run under Xen */
> +    if ( IS_DEFINED(CONFIG_PV) )
> +        return true;
> +
> +    /* HVM tests may additionally run on non-Xen hypervisors or baremetal */
> +    cpuid_count(0x40000000, 0, &eax, &ebx, &ecx, &edx);
> +    if (  ebx == XEN_CPUID_SIGNATURE_EBX &&
> +          ecx == XEN_CPUID_SIGNATURE_ECX &&
> +          edx == XEN_CPUID_SIGNATURE_EDX )
> +        return true;
> +
> +    /* Viridian guests have the Xen leaves higher up, so check there too */
> +    cpuid_count(0x40000100, 0, &eax, &ebx, &ecx, &edx);
> +    return ebx == XEN_CPUID_SIGNATURE_EBX &&
> +           ecx == XEN_CPUID_SIGNATURE_ECX &&
> +           edx == XEN_CPUID_SIGNATURE_EDX;
> +}

This isn't quite correct.  There's a find_xen_leaves() helper which
should do what you want.

~Andrew