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 15:37:40 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...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 10/14/2016 03:16 PM, Konrad Rzeszutek Wilk wrote:
> 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?

For PIC and IOAPIC (and I think RTC too) we will get a warning (with a
splat) that SCI cannot be initialized. But the guest will continue
running without problems.

-boris

>> 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
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@...ts.xen.org
>> https://lists.xen.org/xen-devel