linux-toradex.git/drivers/xen, branch v5.17-rc4

xen/pci: Make use of the helper macro LIST_HEAD()

2022-02-10T10:10:23+00:00

Replace "struct list_head head = LIST_HEAD_INIT(head)" with
"LIST_HEAD(head)" to simplify the code.

Signed-off-by: Cai Huoqing 
Reviewed-by: Juergen Gross 
Link: https://lore.kernel.org/r/20220209032842.38818-1-cai.huoqing@linux.dev
Signed-off-by: Juergen Gross

arm/xen: Read extended regions from DT and init Xen resource

2022-01-06T08:53:41+00:00

This patch implements arch_xen_unpopulated_init() on Arm where
the extended regions (if any) are gathered from DT and inserted
into specific Xen resource to be used as unused address space
for Xen scratch pages by unpopulated-alloc code.

The extended region (safe range) is a region of guest physical
address space which is unused and could be safely used to create
grant/foreign mappings instead of wasting real RAM pages from
the domain memory for establishing these mappings.

The extended regions are chosen by the hypervisor at the domain
creation time and advertised to it via "reg" property under
hypervisor node in the guest device-tree. As region 0 is reserved
for grant table space (always present), the indexes for extended
regions are 1...N.

If arch_xen_unpopulated_init() fails for some reason the default
behaviour will be restored (allocate xenballooned pages).

This patch also removes XEN_UNPOPULATED_ALLOC dependency on x86.

Signed-off-by: Oleksandr Tyshchenko 
Reviewed-by: Stefano Stabellini 
Link: https://lore.kernel.org/r/1639080336-26573-6-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross

xen/unpopulated-alloc: Add mechanism to use Xen resource

2022-01-06T08:53:38+00:00

The main reason of this change is that unpopulated-alloc
code cannot be used in its current form on Arm, but there
is a desire to reuse it to avoid wasting real RAM pages
for the grant/foreign mappings.

The problem is that system "iomem_resource" is used for
the address space allocation, but the really unallocated
space can't be figured out precisely by the domain on Arm
without hypervisor involvement. For example, not all device
I/O regions are known by the time domain starts creating
grant/foreign mappings. And following the advise from
"iomem_resource" we might end up reusing these regions by
a mistake. So, the hypervisor which maintains the P2M for
the domain is in the best position to provide unused regions
of guest physical address space which could be safely used
to create grant/foreign mappings.

Introduce new helper arch_xen_unpopulated_init() which purpose
is to create specific Xen resource based on the memory regions
provided by the hypervisor to be used as unused space for Xen
scratch pages. If arch doesn't define arch_xen_unpopulated_init()
the default "iomem_resource" will be used.

Update the arguments list of allocate_resource() in fill_list()
to always allocate a region from the hotpluggable range
(maximum possible addressable physical memory range for which
the linear mapping could be created). If arch doesn't define
arch_get_mappable_range() the default range (0,-1) will be used.

The behaviour on x86 won't be changed by current patch as both
arch_xen_unpopulated_init() and arch_get_mappable_range()
are not implemented for it.

Also fallback to allocate xenballooned pages (balloon out RAM
pages) if we do not have any suitable resource to work with
(target_resource is invalid) and as the result we won't be able
to provide unpopulated pages on a request.

Signed-off-by: Oleksandr Tyshchenko 
Reviewed-by: Stefano Stabellini 
Link: https://lore.kernel.org/r/1639080336-26573-5-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross

xen/balloon: Bring alloc(free)_xenballooned_pages helpers back

2022-01-06T08:53:35+00:00

This patch rolls back some of the changes introduced by commit
121f2faca2c0a "xen/balloon: rename alloc/free_xenballooned_pages"
in order to make possible to still allocate xenballooned pages
if CONFIG_XEN_UNPOPULATED_ALLOC is enabled.

On Arm the unpopulated pages will be allocated on top of extended
regions provided by Xen via device-tree (the subsequent patches
will add required bits to support unpopulated-alloc feature on Arm).
The problem is that extended regions feature has been introduced
into Xen quite recently (during 4.16 release cycle). So this
effectively means that Linux must only use unpopulated-alloc on Arm
if it is running on "new Xen" which advertises these regions.
But, it will only be known after parsing the "hypervisor" node
at boot time, so before doing that we cannot assume anything.

In order to keep working if CONFIG_XEN_UNPOPULATED_ALLOC is enabled
and the extended regions are not advertised (Linux is running on
"old Xen", etc) we need the fallback to alloc_xenballooned_pages().

This way we wouldn't reduce the amount of memory usable (wasting
RAM pages) for any of the external mappings anymore (and eliminate
XSA-300) with "new Xen", but would be still functional ballooning
out RAM pages with "old Xen".

Also rename alloc(free)_xenballooned_pages to xen_alloc(free)_ballooned_pages
and make xen_alloc(free)_unpopulated_pages static inline in xen.h
if CONFIG_XEN_UNPOPULATED_ALLOC is disabled.

Signed-off-by: Oleksandr Tyshchenko 
Reviewed-by: Stefano Stabellini 
Link: https://lore.kernel.org/r/1639080336-26573-4-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross

xen/unpopulated-alloc: Drop check for virt_addr_valid() in fill_list()

2022-01-06T08:53:15+00:00

If memremap_pages() succeeds the range is guaranteed to have proper page
table, there is no need for an additional virt_addr_valid() check.

Signed-off-by: Oleksandr Tyshchenko 
Reviewed-by: Boris Ostrovsky 
Link: https://lore.kernel.org/r/1639080336-26573-2-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross

xen/gntdev: fix unmap notification order

2022-01-06T07:52:22+00:00

While working with Xen's libxenvchan library I have faced an issue with
unmap notifications sent in wrong order if both UNMAP_NOTIFY_SEND_EVENT
and UNMAP_NOTIFY_CLEAR_BYTE were requested: first we send an event channel
notification and then clear the notification byte which renders in the below
inconsistency (cli_live is the byte which was requested to be cleared on unmap):

[  444.514243] gntdev_put_map UNMAP_NOTIFY_SEND_EVENT map->notify.event 6
libxenvchan_is_open cli_live 1
[  444.515239] __unmap_grant_pages UNMAP_NOTIFY_CLEAR_BYTE at 14

Thus it is not possible to reliably implement the checks like
- wait for the notification (UNMAP_NOTIFY_SEND_EVENT)
- check the variable (UNMAP_NOTIFY_CLEAR_BYTE)
because it is possible that the variable gets checked before it is cleared
by the kernel.

To fix that we need to re-order the notifications, so the variable is first
gets cleared and then the event channel notification is sent.
With this fix I can see the correct order of execution:

[   54.522611] __unmap_grant_pages UNMAP_NOTIFY_CLEAR_BYTE at 14
[   54.537966] gntdev_put_map UNMAP_NOTIFY_SEND_EVENT map->notify.event 6
libxenvchan_is_open cli_live 0

Cc: stable@vger.kernel.org
Signed-off-by: Oleksandr Andrushchenko 
Reviewed-by: Boris Ostrovsky 
Link: https://lore.kernel.org/r/20211210092817.580718-1-andr2000@gmail.com
Signed-off-by: Juergen Gross

xen/console: harden hvc_xen against event channel storms

2021-12-16T07:24:08+00:00

The Xen console driver is still vulnerable for an attack via excessive
number of events sent by the backend. Fix that by using a lateeoi event
channel.

For the normal domU initial console this requires the introduction of
bind_evtchn_to_irq_lateeoi() as there is no xenbus device available
at the time the event channel is bound to the irq.

As the decision whether an interrupt was spurious or not requires to
test for bytes having been read from the backend, move sending the
event into the if statement, as sending an event without having found
any bytes to be read is making no sense at all.

This is part of XSA-391

Signed-off-by: Juergen Gross 
Reviewed-by: Jan Beulich 
---
V2:
- slightly adapt spurious irq detection (Jan Beulich)
V3:
- fix spurious irq detection (Jan Beulich)

xen: detect uninitialized xenbus in xenbus_init

2021-11-24T14:55:15+00:00

If the xenstore page hasn't been allocated properly, reading the value
of the related hvm_param (HVM_PARAM_STORE_PFN) won't actually return
error. Instead, it will succeed and return zero. Instead of attempting
to xen_remap a bad guest physical address, detect this condition and
return early.

Note that although a guest physical address of zero for
HVM_PARAM_STORE_PFN is theoretically possible, it is not a good choice
and zero has never been validly used in that capacity.

Also recognize all bits set as an invalid value.

For 32-bit Linux, any pfn above ULONG_MAX would get truncated. Pfns
above ULONG_MAX should never be passed by the Xen tools to HVM guests
anyway, so check for this condition and return early.

Cc: stable@vger.kernel.org
Signed-off-by: Stefano Stabellini 
Reviewed-by: Juergen Gross 
Reviewed-by: Jan Beulich 
Link: https://lore.kernel.org/r/20211123210748.1910236-1-sstabellini@kernel.org
Signed-off-by: Boris Ostrovsky

xen: flag pvcalls-front to be not essential for system boot

2021-11-23T19:42:20+00:00

The Xen pvcalls device is not essential for booting. Set the respective
flag.

Signed-off-by: Juergen Gross 
Reviewed-by: Boris Ostrovsky 
Link: https://lore.kernel.org/r/20211022064800.14978-5-jgross@suse.com
Signed-off-by: Boris Ostrovsky

xen: add "not_essential" flag to struct xenbus_driver

2021-11-23T19:41:29+00:00

When booting the xenbus driver will wait for PV devices to have
connected to their backends before continuing. The timeout is different
between essential and non-essential devices.

Non-essential devices are identified by their nodenames directly in the
xenbus driver, which requires to update this list in case a new device
type being non-essential is added (this was missed for several types
in the past).

In order to avoid this problem, add a "not_essential" flag to struct
xenbus_driver which can be set to "true" by the respective frontend.

Set this flag for the frontends currently regarded to be not essential
(vkbs and vfb) and use it for testing in the xenbus driver.

Signed-off-by: Juergen Gross 
Link: https://lore.kernel.org/r/20211022064800.14978-2-jgross@suse.com
Reviewed-by: Boris Ostrovsky 
Signed-off-by: Boris Ostrovsky