[PATCH v4 0/3] powerpc/pseries/vas: VAS/NXGZIP support with LPM

[PATCH v4 0/3] powerpc/pseries/vas: VAS/NXGZIP support with LPM

[Haren Myneni]

Virtual Accelerator Switchboard (VAS) is an engine stays on the
chip. So all windows opened on a specific engine belongs to VAS
the chip. The hypervisor expects the partition to close all
active windows on the sources system and reopen them after
migration on the destination machine.

This patch series adds VAS support with the partition migration.
When the migration initiates, the VAS migration handler will be
invoked before pseries_suspend() to close all active windows and
mark them in-active with VAS_WIN_MIGRATE_CLOSE status. Whereas
this migration handler is called after migration to reopen all
windows which has VAS_WIN_MIGRATE_CLOSE status and make them
active again. The user space gets paste instruction failure
when it sends requests on these in-active windows.

These patches depend on VAS/DLPAR support patch series

Changes in v2:
- Added new patch "Define global hv_cop_caps struct" to eliminate
  memory allocation failure during migration (suggestion by
  Nathan Lynch)

Changes in v3:
- Rebase on 5.17-rc4
- Naming changes for VAS capability struct elemets based on the V4 DLPAR
  support patch series.

Changes in v4:
- Rebase on 5.17-rc5
- Include migration_in_progress enable patch in "VAS migration handler"
  and other changes as suggested by Nicholas Piggin 

Haren Myneni (3):
  powerpc/pseries/vas: Define global hv_cop_caps struct
  powerpc/pseries/vas: Modify reconfig open/close functions for
	migration
  powerpc/pseries/vas: Add VAS migration handler

 arch/powerpc/include/asm/vas.h            |   2 +
 arch/powerpc/platforms/pseries/mobility.c |   5 +
 arch/powerpc/platforms/pseries/vas.c      | 233 +++++++++++++++++-----
 arch/powerpc/platforms/pseries/vas.h      |   6 +
 4 files changed, 201 insertions(+), 45 deletions(-)

-- 
2.27.0

[PATCH v4 1/3] powerpc/pseries/vas: Define global hv_cop_caps struct

[Haren Myneni]

The coprocessor capabilities struct is used to get default and
QoS capabilities from the hypervisor during init, DLPAR event and
migration. So instead of allocating this struct for each event,
define global struct and reuse it which allows the migration code
to avoid adding an error path.

Also disable copy/paste feature flag if any capabilities HCALL
is failed.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Acked-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/platforms/pseries/vas.c | 47 ++++++++++++----------------
 1 file changed, 20 insertions(+), 27 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index 591c7597db5a..3bb219f54806 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -26,6 +26,7 @@
 
 static struct vas_all_caps caps_all;
 static bool copypaste_feat;
+static struct hv_vas_cop_feat_caps hv_cop_caps;
 
 static struct vas_caps vascaps[VAS_MAX_FEAT_TYPE];
 static DEFINE_MUTEX(vas_pseries_mutex);
@@ -724,7 +725,6 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds)
  */
 int vas_reconfig_capabilties(u8 type)
 {
-	struct hv_vas_cop_feat_caps *hv_caps;
 	struct vas_cop_feat_caps *caps;
 	int old_nr_creds, new_nr_creds;
 	struct vas_caps *vcaps;
@@ -738,17 +738,13 @@ int vas_reconfig_capabilties(u8 type)
 	vcaps = &vascaps[type];
 	caps = &vcaps->caps;
 
-	hv_caps = kmalloc(sizeof(*hv_caps), GFP_KERNEL);
-	if (!hv_caps)
-		return -ENOMEM;
-
 	mutex_lock(&vas_pseries_mutex);
 	rc = h_query_vas_capabilities(H_QUERY_VAS_CAPABILITIES, vcaps->feat,
-				      (u64)virt_to_phys(hv_caps));
+				      (u64)virt_to_phys(&hv_cop_caps));
 	if (rc)
 		goto out;
 
-	new_nr_creds = be16_to_cpu(hv_caps->target_lpar_creds);
+	new_nr_creds = be16_to_cpu(hv_cop_caps.target_lpar_creds);
 
 	old_nr_creds = atomic_read(&caps->nr_total_credits);
 
@@ -780,7 +776,6 @@ int vas_reconfig_capabilties(u8 type)
 
 out:
 	mutex_unlock(&vas_pseries_mutex);
-	kfree(hv_caps);
 	return rc;
 }
 /*
@@ -822,9 +817,8 @@ static struct notifier_block pseries_vas_nb = {
 
 static int __init pseries_vas_init(void)
 {
-	struct hv_vas_cop_feat_caps *hv_cop_caps;
 	struct hv_vas_all_caps *hv_caps;
-	int rc;
+	int rc = 0;
 
 	/*
 	 * Linux supports user space COPY/PASTE only with Radix
@@ -850,38 +844,37 @@ static int __init pseries_vas_init(void)
 
 	sysfs_pseries_vas_init(&caps_all);
 
-	hv_cop_caps = kmalloc(sizeof(*hv_cop_caps), GFP_KERNEL);
-	if (!hv_cop_caps) {
-		rc = -ENOMEM;
-		goto out;
-	}
 	/*
 	 * QOS capabilities available
 	 */
 	if (caps_all.feat_type & VAS_GZIP_QOS_FEAT_BIT) {
 		rc = get_vas_capabilities(VAS_GZIP_QOS_FEAT,
-					  VAS_GZIP_QOS_FEAT_TYPE, hv_cop_caps);
+					  VAS_GZIP_QOS_FEAT_TYPE, &hv_cop_caps);
 
 		if (rc)
-			goto out_cop;
+			goto out;
 	}
 	/*
 	 * Default capabilities available
 	 */
-	if (caps_all.feat_type & VAS_GZIP_DEF_FEAT_BIT) {
+	if (caps_all.feat_type & VAS_GZIP_DEF_FEAT_BIT)
 		rc = get_vas_capabilities(VAS_GZIP_DEF_FEAT,
-					  VAS_GZIP_DEF_FEAT_TYPE, hv_cop_caps);
-		if (rc)
-			goto out_cop;
-	}
+					  VAS_GZIP_DEF_FEAT_TYPE, &hv_cop_caps);
 
-	if (copypaste_feat && firmware_has_feature(FW_FEATURE_LPAR))
-		of_reconfig_notifier_register(&pseries_vas_nb);
+	if (!rc && copypaste_feat) {
+		if (firmware_has_feature(FW_FEATURE_LPAR))
+			of_reconfig_notifier_register(&pseries_vas_nb);
 
-	pr_info("GZIP feature is available\n");
+		pr_info("GZIP feature is available\n");
+	} else {
+		/*
+		 * Should not happen, but only when get default
+		 * capabilities HCALL failed. So disable copy paste
+		 * feature.
+		 */
+		copypaste_feat = false;
+	}
 
-out_cop:
-	kfree(hv_cop_caps);
 out:
 	kfree(hv_caps);
 	return rc;
-- 
2.27.0

[PATCH v4 2/3] powerpc/pseries/vas: Modify reconfig open/close functions for migration

[Haren Myneni]

VAS is a hardware engine stays on the chip. So when the partition
migrates, all VAS windows on the source system have to be closed
and reopen them on the destination after migration.

The kernel has to consider both DLPAR CPU and migration events to
take action on VAS windows. So using VAS_WIN_NO_CRED_CLOSE and
VAS_WIN_MIGRATE_CLOSE status bits and windows will be reopened
after migration only after both status bits are cleared.

This patch make changes to the current reconfig_open/close_windows
functions to support migration:
- Set VAS_WIN_MIGRATE_CLOSE to the window status when closes and
  reopen windows with the same status during resume.
- Continue to close all windows even if deallocate HCALL failed
  (should not happen) since no way to stop migration with the
  current LPM implementation.
- If the DLPAR CPU event happens while migration is in progress,
  set VAS_WIN_NO_CRED_CLOSE to the window status. Close window
  happens with the first event (migration or DLPAR) and Reopen
  window happens only with the last event (migration or DLPAR).

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
---
 arch/powerpc/include/asm/vas.h       |  2 +
 arch/powerpc/platforms/pseries/vas.c | 88 ++++++++++++++++++++++------
 2 files changed, 73 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
index 6baf7b9ffed4..83afcb6c194b 100644
--- a/arch/powerpc/include/asm/vas.h
+++ b/arch/powerpc/include/asm/vas.h
@@ -36,6 +36,8 @@
 					/* vas mmap() */
 /* Window is closed in the hypervisor due to lost credit */
 #define VAS_WIN_NO_CRED_CLOSE	0x00000001
+/* Window is closed due to migration */
+#define VAS_WIN_MIGRATE_CLOSE	0x00000002
 
 /*
  * Get/Set bit fields
diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index 3bb219f54806..fbcf311da0ec 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -457,11 +457,12 @@ static int vas_deallocate_window(struct vas_window *vwin)
 	mutex_lock(&vas_pseries_mutex);
 	/*
 	 * VAS window is already closed in the hypervisor when
-	 * lost the credit. So just remove the entry from
-	 * the list, remove task references and free vas_window
+	 * lost the credit or with migration. So just remove the entry
+	 * from the list, remove task references and free vas_window
 	 * struct.
 	 */
-	if (win->vas_win.status & VAS_WIN_NO_CRED_CLOSE) {
+	if (!(win->vas_win.status & VAS_WIN_NO_CRED_CLOSE) &&
+		!(win->vas_win.status & VAS_WIN_MIGRATE_CLOSE)) {
 		rc = deallocate_free_window(win);
 		if (rc) {
 			mutex_unlock(&vas_pseries_mutex);
@@ -578,12 +579,14 @@ static int __init get_vas_capabilities(u8 feat, enum vas_cop_feat_type type,
  * by setting the remapping to new paste address if the window is
  * active.
  */
-static int reconfig_open_windows(struct vas_caps *vcaps, int creds)
+static int reconfig_open_windows(struct vas_caps *vcaps, int creds,
+				 bool migrate)
 {
 	long domain[PLPAR_HCALL9_BUFSIZE] = {VAS_DEFAULT_DOMAIN_ID};
 	struct vas_cop_feat_caps *caps = &vcaps->caps;
 	struct pseries_vas_window *win = NULL, *tmp;
 	int rc, mv_ents = 0;
+	int flag;
 
 	/*
 	 * Nothing to do if there are no closed windows.
@@ -602,8 +605,10 @@ static int reconfig_open_windows(struct vas_caps *vcaps, int creds)
 	 * (dedicated). If 1 core is added, this LPAR can have 20 more
 	 * credits. It means the kernel can reopen 20 windows. So move
 	 * 20 entries in the VAS windows lost and reopen next 20 windows.
+	 * For partition migration, reopen all windows that are closed
+	 * during resume.
 	 */
-	if (vcaps->nr_close_wins > creds)
+	if ((vcaps->nr_close_wins > creds) && !migrate)
 		mv_ents = vcaps->nr_close_wins - creds;
 
 	list_for_each_entry_safe(win, tmp, &vcaps->list, win_list) {
@@ -613,12 +618,35 @@ static int reconfig_open_windows(struct vas_caps *vcaps, int creds)
 		mv_ents--;
 	}
 
+	/*
+	 * Open windows if they are closed only with migration or
+	 * DLPAR (lost credit) before.
+	 */
+	if (migrate)
+		flag = VAS_WIN_MIGRATE_CLOSE;
+	else
+		flag = VAS_WIN_NO_CRED_CLOSE;
+
 	list_for_each_entry_safe_from(win, tmp, &vcaps->list, win_list) {
+		/*
+		 * This window is closed with DLPAR and migration events.
+		 * So reopen the window with the last event.
+		 * The user space is not suspended with the current
+		 * migration notifier. So the user space can issue DLPAR
+		 * CPU hotplug while migration in progress. In this case
+		 * this window will be opened with the last event.
+		 */
+		if ((win->vas_win.status & VAS_WIN_NO_CRED_CLOSE) &&
+			(win->vas_win.status & VAS_WIN_MIGRATE_CLOSE)) {
+			win->vas_win.status &= ~flag;
+			continue;
+		}
+
 		/*
 		 * Nothing to do on this window if it is not closed
-		 * with VAS_WIN_NO_CRED_CLOSE
+		 * with this flag
 		 */
-		if (!(win->vas_win.status & VAS_WIN_NO_CRED_CLOSE))
+		if (!(win->vas_win.status & flag))
 			continue;
 
 		rc = allocate_setup_window(win, (u64 *)&domain[0],
@@ -634,7 +662,7 @@ static int reconfig_open_windows(struct vas_caps *vcaps, int creds)
 		/*
 		 * Set window status to active
 		 */
-		win->vas_win.status &= ~VAS_WIN_NO_CRED_CLOSE;
+		win->vas_win.status &= ~flag;
 		mutex_unlock(&win->vas_win.task_ref.mmap_mutex);
 		win->win_type = caps->win_type;
 		if (!--vcaps->nr_close_wins)
@@ -661,20 +689,32 @@ static int reconfig_open_windows(struct vas_caps *vcaps, int creds)
  * the user space to fall back to SW compression and manage with the
  * existing windows.
  */
-static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds)
+static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds,
+									bool migrate)
 {
 	struct pseries_vas_window *win, *tmp;
 	struct vas_user_win_ref *task_ref;
 	struct vm_area_struct *vma;
-	int rc = 0;
+	int rc = 0, flag;
+
+	if (migrate)
+		flag = VAS_WIN_MIGRATE_CLOSE;
+	else
+		flag = VAS_WIN_NO_CRED_CLOSE;
 
 	list_for_each_entry_safe(win, tmp, &vcap->list, win_list) {
 		/*
 		 * This window is already closed due to lost credit
-		 * before. Go for next window.
+		 * or for migration before. Go for next window.
+		 * For migration, nothing to do since this window
+		 * closed for DLPAR and will be reopened even on
+		 * the destination system with other DLPAR operation.
 		 */
-		if (win->vas_win.status & VAS_WIN_NO_CRED_CLOSE)
+		if ((win->vas_win.status & VAS_WIN_MIGRATE_CLOSE) ||
+			(win->vas_win.status & VAS_WIN_NO_CRED_CLOSE)) {
+			win->vas_win.status |= flag;
 			continue;
+		}
 
 		task_ref = &win->vas_win.task_ref;
 		mutex_lock(&task_ref->mmap_mutex);
@@ -683,7 +723,7 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds)
 		 * Number of available credits are reduced, So select
 		 * and close windows.
 		 */
-		win->vas_win.status |= VAS_WIN_NO_CRED_CLOSE;
+		win->vas_win.status |= flag;
 
 		mmap_write_lock(task_ref->mm);
 		/*
@@ -706,12 +746,24 @@ static int reconfig_close_windows(struct vas_caps *vcap, int excess_creds)
 		 * later when the process issued with close(FD).
 		 */
 		rc = deallocate_free_window(win);
-		if (rc)
+		/*
+		 * This failure is from the hypervisor.
+		 * No way to stop migration for these failures.
+		 * So ignore error and continue closing other windows.
+		 */
+		if (rc && !migrate)
 			return rc;
 
 		vcap->nr_close_wins++;
 
-		if (!--excess_creds)
+		/*
+		 * For migration, do not depend on lpar_creds in case if
+		 * mismatch with the hypervisor value (should not happen).
+		 * So close all active windows in the list and will be
+		 * reopened windows based on the new lpar_creds on the
+		 * destination system during resume.
+		 */
+		if (!migrate && !--excess_creds)
 			break;
 	}
 
@@ -761,7 +813,8 @@ int vas_reconfig_capabilties(u8 type)
 		 * target, reopen windows if they are closed due to
 		 * the previous DLPAR (core removal).
 		 */
-		rc = reconfig_open_windows(vcaps, new_nr_creds - old_nr_creds);
+		rc = reconfig_open_windows(vcaps, new_nr_creds - old_nr_creds,
+					   false);
 	} else {
 		/*
 		 * # active windows is more than new LPAR available
@@ -771,7 +824,8 @@ int vas_reconfig_capabilties(u8 type)
 		nr_active_wins = vcaps->nr_open_windows - vcaps->nr_close_wins;
 		if (nr_active_wins > new_nr_creds)
 			rc = reconfig_close_windows(vcaps,
-					nr_active_wins - new_nr_creds);
+					nr_active_wins - new_nr_creds,
+					false);
 	}
 
 out:
-- 
2.27.0

[PATCH v4 3/3] powerpc/pseries/vas: Add VAS migration handler

[Haren Myneni]

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>
---
 arch/powerpc/platforms/pseries/mobility.c |  5 ++
 arch/powerpc/platforms/pseries/vas.c      | 98 ++++++++++++++++++++++-
 arch/powerpc/platforms/pseries/vas.h      |  6 ++
 3 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 85033f392c78..70004243e25e 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -26,6 +26,7 @@
 #include <asm/machdep.h>
 #include <asm/rtas.h>
 #include "pseries.h"
+#include "vas.h"	/* vas_migration_handler() */
 #include "../../kernel/cacheinfo.h"
 
 static struct kobject *mobility_kobj;
@@ -669,12 +670,16 @@ static int pseries_migrate_partition(u64 handle)
 	if (ret)
 		return ret;
 
+	vas_migration_handler(VAS_SUSPEND);
+
 	ret = pseries_suspend(handle);
 	if (ret == 0)
 		post_mobility_fixup();
 	else
 		pseries_cancel_migration(handle, ret);
 
+	vas_migration_handler(VAS_RESUME);
+
 	return ret;
 }
 
diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index fbcf311da0ec..1f59d78c77a1 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -30,6 +30,7 @@ static struct hv_vas_cop_feat_caps hv_cop_caps;
 
 static struct vas_caps vascaps[VAS_MAX_FEAT_TYPE];
 static DEFINE_MUTEX(vas_pseries_mutex);
+static bool migration_in_progress;
 
 static long hcall_return_busy_check(long rc)
 {
@@ -356,7 +357,10 @@ static struct vas_window *vas_allocate_window(int vas_id, u64 flags,
 	 * same fault IRQ is not freed by the OS before.
 	 */
 	mutex_lock(&vas_pseries_mutex);
-	rc = allocate_setup_window(txwin, (u64 *)&domain[0],
+	if (migration_in_progress)
+		rc = -EBUSY;
+	else
+		rc = allocate_setup_window(txwin, (u64 *)&domain[0],
 				   cop_feat_caps->win_type);
 	mutex_unlock(&vas_pseries_mutex);
 	if (rc)
@@ -869,6 +873,98 @@ static struct notifier_block pseries_vas_nb = {
 	.notifier_call = pseries_vas_notifier,
 };
 
+/*
+ * For LPM, all windows have to be closed on the source partition
+ * before migration and reopen them on the destination partition
+ * after migration. So closing windows during suspend and
+ * reopen them during resume.
+ */
+int vas_migration_handler(int action)
+{
+	struct vas_cop_feat_caps *caps;
+	int old_nr_creds, new_nr_creds = 0;
+	struct vas_caps *vcaps;
+	int i, rc = 0;
+
+	/*
+	 * NX-GZIP is not enabled. Nothing to do for migration.
+	 */
+	if (!copypaste_feat)
+		return rc;
+
+	mutex_lock(&vas_pseries_mutex);
+
+	if (action == VAS_SUSPEND)
+		migration_in_progress = true;
+	else
+		migration_in_progress = false;
+
+	for (i = 0; i < VAS_MAX_FEAT_TYPE; i++) {
+		vcaps = &vascaps[i];
+		caps = &vcaps->caps;
+		old_nr_creds = atomic_read(&caps->nr_total_credits);
+
+		rc = h_query_vas_capabilities(H_QUERY_VAS_CAPABILITIES,
+					      vcaps->feat,
+					      (u64)virt_to_phys(&hv_cop_caps));
+		if (!rc) {
+			new_nr_creds = be16_to_cpu(hv_cop_caps.target_lpar_creds);
+			/*
+			 * Should not happen. But incase print messages, close
+			 * all windows in the list during suspend and reopen
+			 * windows based on new lpar_creds on the destination
+			 * system.
+			 */
+			if (old_nr_creds != new_nr_creds) {
+				pr_err("Target credits mismatch with the hypervisor\n");
+				pr_err("state(%d): lpar creds: %d HV lpar creds: %d\n",
+					action, old_nr_creds, new_nr_creds);
+				pr_err("Used creds: %d, Active creds: %d\n",
+					atomic_read(&caps->nr_used_credits),
+					vcaps->nr_open_windows - vcaps->nr_close_wins);
+			}
+		} else {
+			pr_err("state(%d): Get VAS capabilities failed with %d\n",
+				action, rc);
+			/*
+			 * We can not stop migration with the current lpm
+			 * implementation. So continue closing all windows in
+			 * the list (during suspend) and return without
+			 * opening windows (during resume) if VAS capabilities
+			 * HCALL failed.
+			 */
+			if (action == VAS_RESUME)
+				goto out;
+		}
+
+		switch (action) {
+		case VAS_SUSPEND:
+			rc = reconfig_close_windows(vcaps, vcaps->nr_open_windows,
+							true);
+			break;
+		case VAS_RESUME:
+			atomic_set(&caps->nr_total_credits, new_nr_creds);
+			rc = reconfig_open_windows(vcaps, new_nr_creds, true);
+			break;
+		default:
+			/* should not happen */
+			pr_err("Invalid migration action %d\n", action);
+			rc = -EINVAL;
+			goto out;
+		}
+
+		/*
+		 * Ignore errors during suspend and return for resume.
+		 */
+		if (rc && (action == VAS_RESUME))
+			goto out;
+	}
+
+out:
+	mutex_unlock(&vas_pseries_mutex);
+	return rc;
+}
+
 static int __init pseries_vas_init(void)
 {
 	struct hv_vas_all_caps *hv_caps;
diff --git a/arch/powerpc/platforms/pseries/vas.h b/arch/powerpc/platforms/pseries/vas.h
index 4ddb1001a0aa..f7568d8c6ab0 100644
--- a/arch/powerpc/platforms/pseries/vas.h
+++ b/arch/powerpc/platforms/pseries/vas.h
@@ -33,6 +33,11 @@
 #define VAS_GZIP_QOS_CAPABILITIES	0x56516F73477A6970
 #define VAS_GZIP_DEFAULT_CAPABILITIES	0x56446566477A6970
 
+enum vas_migrate_action {
+	VAS_SUSPEND,
+	VAS_RESUME,
+};
+
 /*
  * Co-processor feature - GZIP QoS windows or GZIP default windows
  */
@@ -132,4 +137,5 @@ struct pseries_vas_window {
 int sysfs_add_vas_caps(struct vas_cop_feat_caps *caps);
 int vas_reconfig_capabilties(u8 type);
 int __init sysfs_pseries_vas_init(struct vas_all_caps *vas_caps);
+int vas_migration_handler(int action);
 #endif /* _VAS_H */
-- 
2.27.0

[PATCH v4 3/3] powerpc/pseries/vas: Add VAS migration handler

[Haren Myneni]

[Update: Included the build fix reported by kernel test robot <lkp@intel.com>]

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>
---
 arch/powerpc/platforms/pseries/mobility.c |  5 ++
 arch/powerpc/platforms/pseries/vas.c      | 98 ++++++++++++++++++++++-
 arch/powerpc/platforms/pseries/vas.h      | 14 ++++
 3 files changed, 116 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 85033f392c78..70004243e25e 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -26,6 +26,7 @@
 #include <asm/machdep.h>
 #include <asm/rtas.h>
 #include "pseries.h"
+#include "vas.h"	/* vas_migration_handler() */
 #include "../../kernel/cacheinfo.h"
 
 static struct kobject *mobility_kobj;
@@ -669,12 +670,16 @@ static int pseries_migrate_partition(u64 handle)
 	if (ret)
 		return ret;
 
+	vas_migration_handler(VAS_SUSPEND);
+
 	ret = pseries_suspend(handle);
 	if (ret == 0)
 		post_mobility_fixup();
 	else
 		pseries_cancel_migration(handle, ret);
 
+	vas_migration_handler(VAS_RESUME);
+
 	return ret;
 }
 
diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index fbcf311da0ec..1f59d78c77a1 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -30,6 +30,7 @@ static struct hv_vas_cop_feat_caps hv_cop_caps;
 
 static struct vas_caps vascaps[VAS_MAX_FEAT_TYPE];
 static DEFINE_MUTEX(vas_pseries_mutex);
+static bool migration_in_progress;
 
 static long hcall_return_busy_check(long rc)
 {
@@ -356,7 +357,10 @@ static struct vas_window *vas_allocate_window(int vas_id, u64 flags,
 	 * same fault IRQ is not freed by the OS before.
 	 */
 	mutex_lock(&vas_pseries_mutex);
-	rc = allocate_setup_window(txwin, (u64 *)&domain[0],
+	if (migration_in_progress)
+		rc = -EBUSY;
+	else
+		rc = allocate_setup_window(txwin, (u64 *)&domain[0],
 				   cop_feat_caps->win_type);
 	mutex_unlock(&vas_pseries_mutex);
 	if (rc)
@@ -869,6 +873,98 @@ static struct notifier_block pseries_vas_nb = {
 	.notifier_call = pseries_vas_notifier,
 };
 
+/*
+ * For LPM, all windows have to be closed on the source partition
+ * before migration and reopen them on the destination partition
+ * after migration. So closing windows during suspend and
+ * reopen them during resume.
+ */
+int vas_migration_handler(int action)
+{
+	struct vas_cop_feat_caps *caps;
+	int old_nr_creds, new_nr_creds = 0;
+	struct vas_caps *vcaps;
+	int i, rc = 0;
+
+	/*
+	 * NX-GZIP is not enabled. Nothing to do for migration.
+	 */
+	if (!copypaste_feat)
+		return rc;
+
+	mutex_lock(&vas_pseries_mutex);
+
+	if (action == VAS_SUSPEND)
+		migration_in_progress = true;
+	else
+		migration_in_progress = false;
+
+	for (i = 0; i < VAS_MAX_FEAT_TYPE; i++) {
+		vcaps = &vascaps[i];
+		caps = &vcaps->caps;
+		old_nr_creds = atomic_read(&caps->nr_total_credits);
+
+		rc = h_query_vas_capabilities(H_QUERY_VAS_CAPABILITIES,
+					      vcaps->feat,
+					      (u64)virt_to_phys(&hv_cop_caps));
+		if (!rc) {
+			new_nr_creds = be16_to_cpu(hv_cop_caps.target_lpar_creds);
+			/*
+			 * Should not happen. But incase print messages, close
+			 * all windows in the list during suspend and reopen
+			 * windows based on new lpar_creds on the destination
+			 * system.
+			 */
+			if (old_nr_creds != new_nr_creds) {
+				pr_err("Target credits mismatch with the hypervisor\n");
+				pr_err("state(%d): lpar creds: %d HV lpar creds: %d\n",
+					action, old_nr_creds, new_nr_creds);
+				pr_err("Used creds: %d, Active creds: %d\n",
+					atomic_read(&caps->nr_used_credits),
+					vcaps->nr_open_windows - vcaps->nr_close_wins);
+			}
+		} else {
+			pr_err("state(%d): Get VAS capabilities failed with %d\n",
+				action, rc);
+			/*
+			 * We can not stop migration with the current lpm
+			 * implementation. So continue closing all windows in
+			 * the list (during suspend) and return without
+			 * opening windows (during resume) if VAS capabilities
+			 * HCALL failed.
+			 */
+			if (action == VAS_RESUME)
+				goto out;
+		}
+
+		switch (action) {
+		case VAS_SUSPEND:
+			rc = reconfig_close_windows(vcaps, vcaps->nr_open_windows,
+							true);
+			break;
+		case VAS_RESUME:
+			atomic_set(&caps->nr_total_credits, new_nr_creds);
+			rc = reconfig_open_windows(vcaps, new_nr_creds, true);
+			break;
+		default:
+			/* should not happen */
+			pr_err("Invalid migration action %d\n", action);
+			rc = -EINVAL;
+			goto out;
+		}
+
+		/*
+		 * Ignore errors during suspend and return for resume.
+		 */
+		if (rc && (action == VAS_RESUME))
+			goto out;
+	}
+
+out:
+	mutex_unlock(&vas_pseries_mutex);
+	return rc;
+}
+
 static int __init pseries_vas_init(void)
 {
 	struct hv_vas_all_caps *hv_caps;
diff --git a/arch/powerpc/platforms/pseries/vas.h b/arch/powerpc/platforms/pseries/vas.h
index 4ddb1001a0aa..34177881e998 100644
--- a/arch/powerpc/platforms/pseries/vas.h
+++ b/arch/powerpc/platforms/pseries/vas.h
@@ -33,6 +33,11 @@
 #define VAS_GZIP_QOS_CAPABILITIES	0x56516F73477A6970
 #define VAS_GZIP_DEFAULT_CAPABILITIES	0x56446566477A6970
 
+enum vas_migrate_action {
+	VAS_SUSPEND,
+	VAS_RESUME,
+};
+
 /*
  * Co-processor feature - GZIP QoS windows or GZIP default windows
  */
@@ -132,4 +137,13 @@ struct pseries_vas_window {
 int sysfs_add_vas_caps(struct vas_cop_feat_caps *caps);
 int vas_reconfig_capabilties(u8 type);
 int __init sysfs_pseries_vas_init(struct vas_all_caps *vas_caps);
+
+#ifdef CONFIG_PPC_VAS
+int vas_migration_handler(int action);
+#else
+static inline int vas_migration_handler(int action)
+{
+	return 0;
+}
+#endif
 #endif /* _VAS_H */
-- 
2.27.0

Re: [PATCH v4 0/3] powerpc/pseries/vas: VAS/NXGZIP support with LPM

[Michael Ellerman]

On Sun, 27 Feb 2022 23:46:01 -0800, Haren Myneni wrote:
> Virtual Accelerator Switchboard (VAS) is an engine stays on the
> chip. So all windows opened on a specific engine belongs to VAS
> the chip. The hypervisor expects the partition to close all
> active windows on the sources system and reopen them after
> migration on the destination machine.
> 
> This patch series adds VAS support with the partition migration.
> When the migration initiates, the VAS migration handler will be
> invoked before pseries_suspend() to close all active windows and
> mark them in-active with VAS_WIN_MIGRATE_CLOSE status. Whereas
> this migration handler is called after migration to reopen all
> windows which has VAS_WIN_MIGRATE_CLOSE status and make them
> active again. The user space gets paste instruction failure
> when it sends requests on these in-active windows.
> 
> [...]

Applied to powerpc/next.

[1/3] powerpc/pseries/vas: Define global hv_cop_caps struct
      https://git.kernel.org/powerpc/c/278fe1cc2205a05bfd92c794be3d207372b17289
[2/3] powerpc/pseries/vas: Modify reconfig open/close functions for migration
      https://git.kernel.org/powerpc/c/716d7a2e3764cb79061371767bff1a691adb4e7f
[3/3] powerpc/pseries/vas: Add VAS migration handler
      https://git.kernel.org/powerpc/c/37e6764895ef7431f45ff603a548549d409993d2

cheers