linux-kernel - Re: [PATCH 2/2] xen/pv: Call get_cpu_address_sizes to set x86_virt/phys

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Date:   Sat, 21 Jul 2018 19:17:49 -0400
From:   "M. Vefa Bicakci" <m.v.b@...box.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-kernel@...r.kernel.org
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Juergen Gross <jgross@...e.com>,
        xen-devel@...ts.xenproject.org, x86@...nel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 2/2] xen/pv: Call get_cpu_address_sizes to set
 x86_virt/phys_bits

On 07/21/2018 05:25 PM, Boris Ostrovsky wrote:
> On 07/21/2018 03:49 PM, M. Vefa Bicakci wrote:
>> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
>> index 439a94bf89ad..87afb000142a 100644
>> --- a/arch/x86/xen/enlighten_pv.c
>> +++ b/arch/x86/xen/enlighten_pv.c
>> @@ -1257,6 +1257,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
>>   
>>   	/* Work out if we support NX */
>>   	get_cpu_cap(&boot_cpu_data);
>> +	get_cpu_address_sizes(&boot_cpu_data);
>>   	x86_configure_nx();
> 
> 
> Have you observed any problems without this call? get_cpu_cap() is only
> called here to set X86_FEATURE_NX, and is then called again, together
> with get_cpu_address_sizes(), from early_identify_cpu().

Hello Boris,

Thank you for the reviews! Without the call to get_cpu_address_sizes,
paravirtualized virtual machines do not boot up kernels with versions
4.17 and up at all; this includes dom0 and domU. No domU logs are
generated in dom0's /var/log/xen/console/ directory either, despite
having earlyprintk=xen on the kernel command line for my test domU.

(For the record, I am using the patched version of Xen 4.6.6 provided
by Qubes OS R3.2.)

Thank you,

Vefa