Re: [PATCH 5/7] x86/hyperv: Mark ACPI wakeup mailbox page as private

[Thomas Gleixner <tglx@linutronix.de>]

On Tue, Aug 06 2024 at 15:12, Yunhong Jiang wrote:
> The ACPI wakeup mailbox is accessed by the OS and the firmware, both are
> in the guest's context, instead of the hypervisor/VMM context. Mark the
> address private explicitly.

This lacks information why the realmode area must be reserved and
initialized, which is what the change is doing implicitely.

> Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
>  
> +/*
> + * The ACPI wakeup mailbox are accessed by the OS and the BIOS, both are in the
> + * guest's context, instead of the hypervisor/VMM context.
> + */
> +static bool hv_is_private_mmio_tdx(u64 addr)
> +{
> +	if (wakeup_mailbox_addr && (addr >= wakeup_mailbox_addr &&
> +	    addr < (wakeup_mailbox_addr + PAGE_SIZE)))
> +		return true;
> +	return false;
> +}

static inline bool within_page(u64 addr, u64 start)
{
	return addr >= start && addr < (start + PAGE_SIZE);
}

static bool hv_is_private_mmio_tdx(u64 addr)
{
        return wakeup_mailbox_addr && within_page(addr, wakeup_mailbox_addr)
}

Hmm?

> +
>  void __init hv_vtl_init_platform(void)
>  {
>  	pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
>  
> -	x86_platform.realmode_reserve = x86_init_noop;
> -	x86_platform.realmode_init = x86_init_noop;
> +	if (wakeup_mailbox_addr) {

Wants a comment vs. realmode here.

> +		x86_platform.hyper.is_private_mmio = hv_is_private_mmio_tdx;
> +	} else {
> +		x86_platform.realmode_reserve = x86_init_noop;
> +		x86_platform.realmode_init = x86_init_noop;
> +	}
>  	x86_init.irqs.pre_vector_init = x86_init_noop;
>  	x86_init.timers.timer_init = x86_init_noop;

Thanks,

        tglx