Qubes Settings GUI / setting Initial memory to less than 1/10th Max mem. requires enabling memory balancing

[taradiddles]

[ very low prio ]

Qubes OS version:

4.0rc4

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Steps to reproduce the behavior:

• Choose a VM that is not included in memory balancing (eg. sys-net) and open its Qubes Settings gui / advanced tab
• Try to change the Initial Memory to a lower value than 1/10th the value of the greyed out "Max memory" value.

Expected behavior:

Initial Memory is set to a lower value.

Actual behavior:

Error message - "Initial memory can't be less than one tenth Max Memory". However "Max Memory" is greyed out so one has to enable memory balancing, decrease the max memory, set a lower Initial memory value and then disable memory balancing.

General notes:

IMHO, more generally (= also for VMs with memory balancing enabled) setting a lower value than 1/10th the Max memory should automatically decrease the Max memory to 10 times the new Initial memory value - maybe with a notification message.

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Related issues:

[donob4n]

I had a similar problem. If you try to set more than more 'Max memory', you will get a warning message and the max value will be updated.

https://github.com/QubesOS/qubes-manager/blob/cb2aa56413a85d456af0b2fab10654ccd0186294/qubesmanager/settings.py#L431

This needs to check if the VM is not included in balancing. I've fixed it in my 3.2 dom0 but I considered it pretty dummy for requesting a pull. Also I thought it don't affect Qubes 4.

Probably it shouldn't be called if the VM is not in memory balance.

[donob4n]

I had a similar problem. If you try to set more than more 'Max memory', you will get a warning message and the max value will be updated.

https://github.com/QubesOS/qubes-manager/blob/cb2aa56413a85d456af0b2fab10654ccd0186294/qubesmanager/settings.py#L431

This needs to check if the VM is not included in balancing. I've fixed it in my 3.2 dom0 but I considered it pretty dummy for requesting a pull. Also I thought it don't affect Qubes 4.

Probably it shouldn't be called if the VM is not in memory balance.

[donob4n]

It's hard to avoid it being called since it's called by the gui, so maybe a good solution could be:

def check_mem_changes(self):
    # skip VMs not included in memory balancing
    if not self.include_in_balancing.isChecked()
        self.max_mem_size.setValue(self.init_mem.value())
        return

    if self.max_mem_size.value() < self.init_mem.value():
        QtGui.QMessageBox.warning(
            None,
            self.tr("Warning!"),
            self.tr("Max memory can not be less than initial memory.<br>"
                    "Setting max memory to equal initial memory."))
        self.max_mem_size.setValue(self.init_mem.value())
    # Linux specific limit: init memory must not be below
    # max_mem_size/10.79 in order to allow scaling up to
    # max_mem_size (or else "add_memory() failed: -17" problem)
    if self.init_mem.value() * 10 < self.max_mem_size.value():
        QtGui.QMessageBox.warning(
            None,
            self.tr("Warning!"),
            self.tr("Initial memory can not be less than one tenth "
                    "Max memory.<br>Setting initial memory to the minimum "
                    "allowed value."))
        self.init_mem.setValue(self.max_mem_size.value() / 10)

[donob4n]

It's hard to avoid it being called since it's called by the gui, so maybe a good solution could be:

def check_mem_changes(self):
    # skip VMs not included in memory balancing
    if not self.include_in_balancing.isChecked()
        self.max_mem_size.setValue(self.init_mem.value())
        return

    if self.max_mem_size.value() < self.init_mem.value():
        QtGui.QMessageBox.warning(
            None,
            self.tr("Warning!"),
            self.tr("Max memory can not be less than initial memory.<br>"
                    "Setting max memory to equal initial memory."))
        self.max_mem_size.setValue(self.init_mem.value())
    # Linux specific limit: init memory must not be below
    # max_mem_size/10.79 in order to allow scaling up to
    # max_mem_size (or else "add_memory() failed: -17" problem)
    if self.init_mem.value() * 10 < self.max_mem_size.value():
        QtGui.QMessageBox.warning(
            None,
            self.tr("Warning!"),
            self.tr("Initial memory can not be less than one tenth "
                    "Max memory.<br>Setting initial memory to the minimum "
                    "allowed value."))
        self.init_mem.setValue(self.max_mem_size.value() / 10)