linux-kernel - Re: [PATCH v3] xen/balloon: add late_initcall

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Message-ID: <c5da2698-b160-c09e-3182-49b398238a3c@suse.com>
Date:   Mon, 1 Nov 2021 08:15:24 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     Stefano Stabellini <sstabellini@...nel.org>,
        stable@...r.kernel.org,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
Subject: Re: [PATCH v3] xen/balloon: add late_initcall_sync() for initial
 ballooning done

On 29.10.21 23:46, Boris Ostrovsky wrote:
> 
> On 10/29/21 10:20 AM, Juergen Gross wrote:
>> --- a/Documentation/ABI/stable/sysfs-devices-system-xen_memory
>> +++ b/Documentation/ABI/stable/sysfs-devices-system-xen_memory
>> @@ -84,3 +84,13 @@ Description:
>>           Control scrubbing pages before returning them to Xen for 
>> others domains
>>           use. Can be set with xen_scrub_pages cmdline
>>           parameter. Default value controlled with 
>> CONFIG_XEN_SCRUB_PAGES_DEFAULT.
>> +
>> +What:        /sys/devices/system/xen_memory/xen_memory0/boot_timeout
>> +Date:        November 2021
>> +KernelVersion:    5.16
>> +Contact:    xen-devel@...ts.xenproject.org
>> +Description:
>> +        The time (in seconds) to wait before giving up to boot in case
>> +        initial ballooning fails to free enough memory. Applies only
>> +        when running as HVM or PVH guest and started with less memory
>> +        configured than allowed at max.
> 
> 
> How is this going to be used? We only need this during boot.

Of course. Will switch to module_param().

>> -        state = update_schedule(state);
>> +        balloon_state = update_schedule(balloon_state);
> 
> 
> Now that balloon_state has whole file scope it can probably be updated 
> inside update_schedule().

I can do that.

>> +    while ((credit = current_credit()) < 0) {
>> +        if (credit != last_credit) {
>> +            last_changed = jiffies;
>> +            last_credit = credit;
>> +        }
>> +        if (balloon_state == BP_ECANCELED) {
> 
> 
> What about other states? We are really waiting for BP_DONE, aren't we?

Nearly. We are waiting for credit not being negative.

And in case of cancelled we know this won't happen without Xen admin
intervention.


Juergen

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