powerpc/pseries/vas: Migration suspend waits for no in-progress open windows

The hypervisor returns migration failure if all VAS windows are not
closed. During pre-migration stage, vas_migration_handler() sets
migration_in_progress flag and closes all windows from the list.
The allocate VAS window routine checks the migration flag, setup
the window and then add it to the list. So there is possibility of
the migration handler missing the window that is still in the
process of setup.

t1: Allocate and open VAS t2: Migration event
window

lock vas_pseries_mutex
If migration_in_progress set
unlock vas_pseries_mutex
return
open window HCALL
unlock vas_pseries_mutex
Modify window HCALL lock vas_pseries_mutex
setup window migration_in_progress=true
Closes all windows from the list
// May miss windows that are
// not in the list
unlock vas_pseries_mutex
lock vas_pseries_mutex return
if nr_closed_windows == 0
// No DLPAR CPU or migration
add window to the list
// Window will be added to the
// list after the setup is completed
unlock vas_pseries_mutex
return
unlock vas_pseries_mutex
Close VAS window
// due to DLPAR CPU or migration
return -EBUSY

This patch resolves the issue with the following steps:
- Set the migration_in_progress flag without holding mutex.
- Introduce nr_open_wins_progress counter in VAS capabilities
struct
- This counter tracks the number of open windows are still in
progress
- The allocate setup window thread closes windows if the migration
is set and decrements nr_open_window_progress counter
- The migration handler waits for no in-progress open windows.

The code flow with the fix is as follows:

t1: Allocate and open VAS t2: Migration event
window

lock vas_pseries_mutex
If migration_in_progress set
unlock vas_pseries_mutex
return
open window HCALL
nr_open_wins_progress++
// Window opened, but not
// added to the list yet
unlock vas_pseries_mutex
Modify window HCALL migration_in_progress=true
setup window lock vas_pseries_mutex
Closes all windows from the list
While nr_open_wins_progress {
unlock vas_pseries_mutex
lock vas_pseries_mutex sleep
if nr_closed_windows == 0 // Wait if any open window in
or migration is not started // progress. The open window
// No DLPAR CPU or migration // thread closes the window without
add window to the list // adding to the list and return if
nr_open_wins_progress-- // the migration is in progress.
unlock vas_pseries_mutex
return
Close VAS window
nr_open_wins_progress--
unlock vas_pseries_mutex
return -EBUSY lock vas_pseries_mutex
}
unlock vas_pseries_mutex
return

Fixes: 37e6764895ef ("powerpc/pseries/vas: Add VAS migration handler")
Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231125235104.3405008-1-haren@linux.ibm.com

powerpc/pseries: Use lparcfg to reconfig VAS windows for DLPAR CPU

The hypervisor assigns VAS (Virtual Accelerator Switchboard)
windows depends on cores configured in LPAR. The kernel uses
OF reconfig notifier to reconfig VAS windows for DLPAR CPU event.
In the case of shared CPU mode partition, the hypervisor assigns
VAS windows depends on CPU entitled capacity, not based on vcpus.
When the user changes CPU entitled capacity for the partition,
drmgr uses /proc/ppc64/lparcfg interface to notify the kernel.

This patch adds the following changes to update VAS resources
for shared mode:
- Call vas reconfig windows from lparcfg_write()
- Ignore reconfig changes in the VAS notifier

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
[mpe: Rework error handling, report any errors as EIO]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/efa9c16e4a78dda4567a16f13dabfd73cb4674a2.camel@linux.ibm.com

powerpc/pseries/vas: Add VAS IRQ primary handler

irq_default_primary_handler() can be used only with IRQF_ONESHOT
flag, but the flag disables IRQ before executing the thread handler
and enables it after the interrupt is handled. But this IRQ disable
sets the VAS IRQ OFF state in the hypervisor. In case if NX faults
during this window, the hypervisor will not deliver the fault
interrupt to the partition and the user space may wait continuously
for the CSB update. So use VAS specific IRQ handler instead of
calling the default primary handler.

Increment pending_faults counter in IRQ handler and the bottom
thread handler will process all faults based on this counter.
In case if the another interrupt is received while the thread is
running, it will be processed using this counter. The synchronization
of top and bottom handlers will be done with IRQTF_RUNTHREAD flag
and will re-enter to bottom half if this flag is set.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/aaad8813b4762a6753cfcd0b605a7574a5192ec7.camel@linux.ibm.com

powerpc/pseries/vas: Use QoS credits from the userspace

The user can change the QoS credits dynamically with the
management console interface which notifies OS with sysfs. After
returning from the OS interface successfully, the management
console updates the hypervisor. Since the VAS capabilities in
the hypervisor is not updated when the OS gets the update,
the kernel is using the old total credits value from the
hypervisor. Fix this issue by using the new QoS credits
from the userspace instead of depending on VAS capabilities
from the hypervisor.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/76d156f8af1e03cc09369d68e0bfad0c40031bcc.camel@linux.ibm.com

powerpc/pseries/vas: Add VAS migration handler

Since the VAS windows belong to the VAS hardware resource, the
hypervisor expects the partition to close them on source partition
and reopen them after the partition migrated on the destination
machine.

This handler is called before pseries_suspend() to close these
windows and again invoked after migration. All active windows
for both default and QoS types will be closed and mark them
inactive and reopened after migration with this handler.
During the migration, the user space receives paste instruction
failure if it issues copy/paste on these inactive windows.

The current migration implementation does not freeze the user
space and applications can continue to open VAS windows while
migration is in progress. So when the migration_in_progress flag
is set, VAS open window API returns -EBUSY.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/05e45ff4f8babd2490ccb7ae923884f4aa21a7e5.camel@linux.ibm.com

powerpc/pseries/vas: Add 'update_total_credits' entry for QoS capabilities

pseries supports two types of credits - Default (uses normal priority
FIFO) and Qality of service (QoS uses high priority FIFO). The user
decides the number of QoS credits and sets this value with HMC
interface. The total credits for QoS capabilities can be changed
dynamically with HMC interface which invokes drmgr to communicate
to the kernel.

This patch creats 'update_total_credits' entry for QoS capabilities
so that drmgr command can write the new target QoS credits in sysfs.
Instead of using this value, the kernel gets the new QoS capabilities
from the hypervisor whenever update_total_credits is updated to make
sure sync with the QoS target credits in the hypervisor.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b01ef31a0f964686d00243e7de7f09c73c07e69e.camel@linux.ibm.com

powerpc/pseries/vas: sysfs interface to export capabilities

The hypervisor provides the available VAS GZIP capabilities such
as default or QoS window type and the target available credits in
each type. This patch creates sysfs entries and exports the target,
used and the available credits for each feature.

This interface can be used by the user space to determine the credits
usage or to set the target credits in the case of QoS type (for DLPAR).

/sys/devices/vas/vas0/gzip/default_capabilities (default GZIP capabilities)
nr_total_credits /* Total credits available. Can be
/* changed with DLPAR operation */
nr_used_credits /* Used credits */

/sys/devices/vas/vas0/gzip/qos_capabilities (QoS GZIP capabilities)
nr_total_credits
nr_used_credits

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/702d8b626ebfac2b52f4995eebeafe1c9a6fcb75.camel@linux.ibm.com

powerpc/pseries/vas: Close windows with DLPAR core removal

The hypervisor assigns vas credits (windows) for each LPAR based
on the number of cores configured in that system. The OS is
expected to release credits when cores are removed, and may
allocate more when cores are added. So there is a possibility of
using excessive credits (windows) in the LPAR and the hypervisor
expects the system to close the excessive windows so that NX load
can be equally distributed across all LPARs in the system.

When the OS closes the excessive windows in the hypervisor,
it sets the window status inactive and invalidates window
virtual address mapping. The user space receives paste instruction
failure if any NX requests are issued on the inactive window.
Then the user space can use with the available open windows or
retry NX requests until this window active again.

This patch also adds the notifier for core removal/add to close
windows in the hypervisor if the system lost credits (core
removal) and reopen windows in the hypervisor when the previously
lost credits are available.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/108928f9c00a48cc6a722315d482d07cf66acf5a.camel@linux.ibm.com

powerpc/pseries/vas: Save PID in pseries_vas_window struct

The kernel sets the VAS window with PID when it is opened in
the hypervisor. During DLPAR operation, windows can be closed and
reopened in the hypervisor when the credit is available. So saves
this PID in pseries_vas_window struct when the window is opened
initially and reuse it later during DLPAR operation.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a57cbe6d292fe49ad55a0b49c5679d6a24d8fe73.camel@linux.ibm.com

powerpc/pseries/vas: Use common names in VAS capability structure

nr_total/nr_used_credits provides credits usage to user space
via sysfs and the same interface can be used on PowerNV in
future. Changed with proper naming so that applicable on both
pseries and PowerNV.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f4313e9f198ee4f8d4fa4d015d8d1873e17851e6.camel@linux.ibm.com

powerpc/pseries/vas: Define VAS/NXGZIP hcalls and structs

This patch adds hcalls and other definitions. Also define structs
that are used in VAS implementation on PowerVM.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b4b8c594c27ee4aa6be9dc6dc4ee7331571cbbe8.camel@linux.ibm.com