linux-kernel - Re: [Xen-devel] [PATCH 5/8] xen/pvh: Prevent PVH guests from using PIC, RTC and IOAPIC

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Date:   Fri, 14 Oct 2016 15:16:13 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     david.vrabel@...rix.com, JGross@...e.com,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        roger.pau@...rix.com
Subject: Re: [Xen-devel] [PATCH 5/8] xen/pvh: Prevent PVH guests from using
 PIC, RTC and IOAPIC

On Fri, Oct 14, 2016 at 02:05:15PM -0400, Boris Ostrovsky wrote:
> Make sure they don't use these devices since they are not emulated
> for unprivileged PVH guest.

Which means they would just return 0 ? Or would it get worst since
the in/out would go to the hypervisor which would kill the guest?
> 
> Also don't initialize hypercall page for them in init_hvm_pv_info()
> since this has already been done.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> ---
>  arch/x86/xen/enlighten.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index d38d568..6c1a330 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1803,10 +1803,21 @@ static void __init init_hvm_pv_info(void)
>  	minor = eax & 0xffff;
>  	printk(KERN_INFO "Xen version %d.%d.\n", major, minor);
>  
> -	cpuid(base + 2, &pages, &msr, &ecx, &edx);
> +	xen_domain_type = XEN_HVM_DOMAIN;
>  
> -	pfn = __pa(hypercall_page);
> -	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
> +	/* PVH set up hypercall page earlier in xen_prepare_pvh() */

A period at the end?
> +	if (xen_pvh_domain()) {
> +		pv_info.name = "Xen PVH";
> +#ifdef CONFIG_ACPI
> +		/* No PIC or IOAPIC */

Here?
> +		acpi_irq_model = ACPI_IRQ_MODEL_PLATFORM;
> +#endif
> +	} else {
> +		pv_info.name = "Xen HVM";
> +		cpuid(base + 2, &pages, &msr, &ecx, &edx);

Could you use cpuid_ebx ?
> +		pfn = __pa(hypercall_page);
> +		wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
> +	}
>  
>  	xen_setup_features();
>  
> @@ -1815,10 +1826,6 @@ static void __init init_hvm_pv_info(void)
>  		this_cpu_write(xen_vcpu_id, ebx);
>  	else
>  		this_cpu_write(xen_vcpu_id, smp_processor_id());
> -
> -	pv_info.name = "Xen HVM";
> -
> -	xen_domain_type = XEN_HVM_DOMAIN;
>  }
>  
>  static int xen_cpu_up_prepare(unsigned int cpu)
> @@ -1892,6 +1899,9 @@ static void __init xen_hvm_guest_init(void)
>  
>  	init_hvm_pv_info();
>  
> +	if (xen_pvh_domain())
> +		x86_platform.legacy.rtc = 0;
> +
>  	xen_hvm_init_shared_info();
>  
>  	xen_panic_handler_init();
> -- 
> 1.8.3.1
> 
> 
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