[pve-devel] [PATCH v9 qemu-server 5/6] fix #2318: allow phys-bits and host-phys-bits CPU settings

[Stefan Reiter]

On 06/04/2020 14:34, Fabian Ebner wrote:
> On 26.03.20 16:13, Stefan Reiter wrote:
>> Can be specified for a particular VM or via a custom CPU model (VM takes
>> precedence).
>>
>> QEMU's default limit only allows up to 1TB of RAM per VM. Increasing the
>> physical address bits available to a VM can fix this.
>>
>> Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
>> ---
>>   PVE/QemuServer/CPUConfig.pm | 24 ++++++++++++++++++++++++
>>   1 file changed, 24 insertions(+)
>>
>> diff --git a/PVE/QemuServer/CPUConfig.pm b/PVE/QemuServer/CPUConfig.pm
>> index fa09f4b..2b2529d 100644
>> --- a/PVE/QemuServer/CPUConfig.pm
>> +++ b/PVE/QemuServer/CPUConfig.pm
>> @@ -149,6 +149,19 @@ my $cpu_fmt = {
>>       pattern => qr/$cpu_flag_any_re(;$cpu_flag_any_re)*/,
>>       optional => 1,
>>       },
>> +    'phys-bits' => {
>> +    type => 'integer',
>> +    minimum => 8,
>> +    maximum => 64,
>> +    description => "The physical memory address bits that are 
>> reported to the guest OS. Should be smaller or equal to the host's.",
>> +    optional => 1,
>> +    },
>> +    'host-phys-bits' => {
>> +    type => 'boolean',
>> +    default => 0,
>> +    description => "Whether to report the host's physical memory 
>> address bits. Overrides 'phys-bits' when set.",
> 
> Is it better to die when both are set, so that a user gets informed 
> about the clashing options?
> 

Actually, how do you feel about making this a single 'string' option 
'phys-bits' and allowing /^(host|\d{1,2})$/ ? Would mean that min/max(?) 
int values had to be checked manually, but I think it would make it 
clearer for the user.

>> +    optional => 1,
>> +    },
>>   };
>>   # $cpu_fmt describes both the CPU config passed as part of a VM 
>> config, as well
>> @@ -472,6 +485,17 @@ sub get_cpu_options {
>>       $cpu_str .= resolve_cpu_flags($pve_flags, $hv_flags, 
>> $custom_cputype_flags,
>>                     $vm_flags, $pve_forced_flags);
>> +    my $phys_bits = '';
>> +    foreach my $conf ($custom_cpu, $cpu) {
>> +    next if !defined($conf);
>> +    if ($conf->{'host-phys-bits'}) {
>> +        $phys_bits = ",host-phys-bits=true";
>> +    } elsif ($conf->{'phys-bits'}) {
>> +        $phys_bits = ",phys-bits=$conf->{'phys-bits'}";
>> +    }
>> +    }
>> +    $cpu_str .= $phys_bits;
>> +
>>       return ('-cpu', $cpu_str);
>>   }
>>