Re: [PATCH v6 4/4] x86/xen: Add "nopv" support for HVM guest

[Boris Ostrovsky]

On 7/9/19 12:20 AM, Zhenzhong Duan wrote:
>
> -const __initconst struct hypervisor_x86 x86_hyper_xen_hvm = {
> +static uint32_t __init xen_platform_hvm(void)
> +{
> +ÂÂÂÂÂÂ uint32_t xen_domain = xen_cpuid_base();
> +ÂÂÂÂÂÂ struct x86_hyper_init *h = &x86_hyper_xen_hvm.init;
> +
> +ÂÂÂÂÂÂ if (xen_pv_domain())
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return 0;
> +
> +ÂÂÂÂÂÂ if (xen_pvh_domain() && nopv) {
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /* Guest booting via the Xen-PVH boot entry goes here */
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_info("\"nopv\" parameter is ignored in PVH guest\n");
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ nopv = false;
> +ÂÂÂÂÂÂ } else if (nopv && xen_domain) {
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /*
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * Guest booting via normal boot entry (like via
> grub2) goes
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * here.
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ *
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * Use interface functions for bare hardware if nopv,
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * xen_hvm_guest_late_init is an exception as we need to
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * detect PVH and panic there.
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ */
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ memcpy(h, (void *)&x86_init.hyper,
> sizeof(x86_init.hyper));


And this worked? I'd think it would fail since h points to RO section.


> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ memcpy(&x86_hyper_xen_hvm.runtime, (void
> *)&x86_platform.hyper,
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ sizeof(x86_platform.hyper));
> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ h->guest_late_init = xen_hvm_guest_late_init;


To me this still doesn't look right --- you are making assumptions about
x86_platform/x86_init.hyper and I don't think you can assume they have
not been set to point to another hypervisor, for example.

Would modifying all x86_hyper_xen_hvm's ops (except, I guess,
xen_hvm_guest_late_init()) to immediately return if nopv is set work?

Also question for Juergen --- is there anything perhaps in zeropage that
indicates we are booting PVH guest from grub?

-boris


> +ÂÂÂÂÂÂ }
> +ÂÂÂÂÂÂ return xen_domain;
> +}
> +
> +struct hypervisor_x86 x86_hyper_xen_hvm __initdata = {
> ÂÂÂÂÂÂÂ .nameÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ = "Xen HVM",
> ÂÂÂÂÂÂÂ .detectÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ = xen_platform_hvm,
> ÂÂÂÂÂÂÂ .typeÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ = X86_HYPER_XEN_HVM,
> @@ -268,4 +292,5 @@ static __init void xen_hvm_guest_late_init(void)
>  .init.init_mem_mapping = xen_hvm_init_mem_mapping,
> ÂÂÂÂÂÂÂ .init.guest_late_initÂÂ = xen_hvm_guest_late_init,
> ÂÂÂÂÂÂÂ .runtime.pin_vcpuÂÂÂÂÂÂ = xen_pin_vcpu,
> +ÂÂÂÂÂÂ .ignore_nopvÂÂÂÂÂÂÂÂÂÂÂ = true,
> Â};
>
>
> Thanks
>
> Zhenzhong
>