[GIT PULL 1/9] KVM: s390: CMMA tracking, ESSA emulation, migration mode

Christian Borntraeger
2017-06-28T17:30:36Z

From: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>

* Add a migration state bitmap to keep track of which pages have dirty
CMMA information.
* Disable CMMA by default, so we can track if it's used or not. Enable
it on first use like we do for storage keys (unless we are doing a
migration).
* Creates a VM attribute to enter and leave migration mode.
* In migration mode, CMMA is disabled in the SIE block, so ESSA is
always interpreted and emulated in software.
* Free the migration state on VM destroy.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
Documentation/virtual/kvm/devices/vm.txt | 33 +++++++
arch/s390/include/asm/kvm_host.h | 9 ++
arch/s390/include/uapi/asm/kvm.h | 6 ++
arch/s390/kvm/kvm-s390.c | 159 ++++++++++++++++++++++++++++++-
arch/s390/kvm/priv.c | 103 +++++++++++++++++++-
5 files changed, 304 insertions(+), 6 deletions(-)

diff --git a/Documentation/virtual/kvm/devices/vm.txt b/Documentation/virtual/kvm/devices/vm.txt
index 575ccb0..903fc92 100644
--- a/Documentation/virtual/kvm/devices/vm.txt
+++ b/Documentation/virtual/kvm/devices/vm.txt
@@ -222,3 +222,36 @@ Allows user space to disable dea key wrapping, clearing the wrapping key.

Parameters: none
Returns: 0
+
+5. GROUP: KVM_S390_VM_MIGRATION
+Architectures: s390
+
+5.1. ATTRIBUTE: KVM_S390_VM_MIGRATION_STOP (w/o)
+
+Allows userspace to stop migration mode, needed for PGSTE migration.
+Setting this attribute when migration mode is not active will have no
+effects.
+
+Parameters: none
+Returns: 0
+
+5.2. ATTRIBUTE: KVM_S390_VM_MIGRATION_START (w/o)
+
+Allows userspace to start migration mode, needed for PGSTE migration.
+Setting this attribute when migration mode is already active will have
+no effects.
+
+Parameters: none
+Returns: -ENOMEM if there is not enough free memory to start migration mode
+ -EINVAL if the state of the VM is invalid (e.g. no memory defined)
+ 0 in case of success.
+
+5.3. ATTRIBUTE: KVM_S390_VM_MIGRATION_STATUS (r/o)
+
+Allows userspace to query the status of migration mode.
+
+Parameters: address of a buffer in user space to store the data (u64) to;
+ the data itself is either 0 if migration mode is disabled or 1
+ if it is enabled
+Returns: -EFAULT if the given address is not accessible from kernel space
+ 0 in case of success.
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 426614a..a8cafed 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -45,6 +45,8 @@
#define KVM_REQ_ENABLE_IBS 8
#define KVM_REQ_DISABLE_IBS 9
#define KVM_REQ_ICPT_OPEREXC 10
+#define KVM_REQ_START_MIGRATION 11
+#define KVM_REQ_STOP_MIGRATION 12

#define SIGP_CTRL_C 0x80
#define SIGP_CTRL_SCN_MASK 0x3f
@@ -691,6 +693,12 @@ struct kvm_s390_vsie {
struct page *pages[KVM_MAX_VCPUS];
};

+struct kvm_s390_migration_state {
+ unsigned long bitmap_size; /* in bits (number of guest pages) */
+ atomic64_t dirty_pages; /* number of dirty pages */
+ unsigned long *pgste_bitmap;
+};
+
struct kvm_arch{
void *sca;
int use_esca;
@@ -718,6 +726,7 @@ struct kvm_arch{
struct kvm_s390_crypto crypto;
struct kvm_s390_vsie vsie;
u64 epoch;
+ struct kvm_s390_migration_state *migration_state;
/* subset of available cpu features enabled by user space */
DECLARE_BITMAP(cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS);
};
diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 3dd2a1d..d6879a9 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -70,6 +70,7 @@ struct kvm_s390_io_adapter_req {
#define KVM_S390_VM_TOD 1
#define KVM_S390_VM_CRYPTO 2
#define KVM_S390_VM_CPU_MODEL 3
+#define KVM_S390_VM_MIGRATION 4

/* kvm attributes for mem_ctrl */
#define KVM_S390_VM_MEM_ENABLE_CMMA 0
@@ -151,6 +152,11 @@ struct kvm_s390_vm_cpu_subfunc {
#define KVM_S390_VM_CRYPTO_DISABLE_AES_KW 2
#define KVM_S390_VM_CRYPTO_DISABLE_DEA_KW 3

+/* kvm attributes for migration mode */
+#define KVM_S390_VM_MIGRATION_STOP 0
+#define KVM_S390_VM_MIGRATION_START 1
+#define KVM_S390_VM_MIGRATION_STATUS 2
+
/* for KVM_GET_REGS and KVM_SET_REGS */
struct kvm_regs {
/* general purpose regs for s390 */
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 689ac48..c2b3914 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -31,6 +31,7 @@
#include <linux/bitmap.h>
#include <linux/sched/signal.h>

+#include <linux/string.h>
#include <asm/asm-offsets.h>
#include <asm/lowcore.h>
#include <asm/stp.h>
@@ -750,6 +751,129 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
return 0;
}

+static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
+{
+ int cx;
+ struct kvm_vcpu *vcpu;
+
+ kvm_for_each_vcpu(cx, vcpu, kvm)
+ kvm_s390_sync_request(req, vcpu);
+}
+
+/*
+ * Must be called with kvm->srcu held to avoid races on memslots, and with
+ * kvm->lock to avoid races with ourselves and kvm_s390_vm_stop_migration.
+ */
+static int kvm_s390_vm_start_migration(struct kvm *kvm)
+{
+ struct kvm_s390_migration_state *mgs;
+ struct kvm_memory_slot *ms;
+ /* should be the only one */
+ struct kvm_memslots *slots;
+ unsigned long ram_pages;
+ int slotnr;
+
+ /* migration mode already enabled */
+ if (kvm->arch.migration_state)
+ return 0;
+
+ slots = kvm_memslots(kvm);
+ if (!slots || !slots->used_slots)
+ return -EINVAL;
+
+ mgs = kzalloc(sizeof(*mgs), GFP_KERNEL);
+ if (!mgs)
+ return -ENOMEM;
+ kvm->arch.migration_state = mgs;
+
+ if (kvm->arch.use_cmma) {
+ /*
+ * Get the last slot. They should be sorted by base_gfn, so the
+ * last slot is also the one at the end of the address space.
+ * We have verified above that at least one slot is present.
+ */
+ ms = slots->memslots + slots->used_slots - 1;
+ /* round up so we only use full longs */
+ ram_pages = roundup(ms->base_gfn + ms->npages, BITS_PER_LONG);
+ /* allocate enough bytes to store all the bits */
+ mgs->pgste_bitmap = vmalloc(ram_pages / 8);
+ if (!mgs->pgste_bitmap) {
+ kfree(mgs);
+ kvm->arch.migration_state = NULL;
+ return -ENOMEM;
+ }
+
+ mgs->bitmap_size = ram_pages;
+ atomic64_set(&mgs->dirty_pages, ram_pages);
+ /* mark all the pages in active slots as dirty */
+ for (slotnr = 0; slotnr < slots->used_slots; slotnr++) {
+ ms = slots->memslots + slotnr;
+ bitmap_set(mgs->pgste_bitmap, ms->base_gfn, ms->npages);
+ }
+
+ kvm_s390_sync_request_broadcast(kvm, KVM_REQ_START_MIGRATION);
+ }
+ return 0;
+}
+
+/*
+ * Must be called with kvm->lock to avoid races with ourselves and
+ * kvm_s390_vm_start_migration.
+ */
+static int kvm_s390_vm_stop_migration(struct kvm *kvm)
+{
+ struct kvm_s390_migration_state *mgs;
+
+ /* migration mode already disabled */
+ if (!kvm->arch.migration_state)
+ return 0;
+ mgs = kvm->arch.migration_state;
+ kvm->arch.migration_state = NULL;
+
+ if (kvm->arch.use_cmma) {
+ kvm_s390_sync_request_broadcast(kvm, KVM_REQ_STOP_MIGRATION);
+ vfree(mgs->pgste_bitmap);
+ }
+ kfree(mgs);
+ return 0;
+}
+
+static int kvm_s390_vm_set_migration(struct kvm *kvm,
+ struct kvm_device_attr *attr)
+{
+ int idx, res = -ENXIO;
+
+ mutex_lock(&kvm->lock);
+ switch (attr->attr) {
+ case KVM_S390_VM_MIGRATION_START:
+ idx = srcu_read_lock(&kvm->srcu);
+ res = kvm_s390_vm_start_migration(kvm);
+ srcu_read_unlock(&kvm->srcu, idx);
+ break;
+ case KVM_S390_VM_MIGRATION_STOP:
+ res = kvm_s390_vm_stop_migration(kvm);
+ break;
+ default:
+ break;
+ }
+ mutex_unlock(&kvm->lock);
+
+ return res;
+}
+
+static int kvm_s390_vm_get_migration(struct kvm *kvm,
+ struct kvm_device_attr *attr)
+{
+ u64 mig = (kvm->arch.migration_state != NULL);
+
+ if (attr->attr != KVM_S390_VM_MIGRATION_STATUS)
+ return -ENXIO;
+
+ if (copy_to_user((void __user *)attr->addr, &mig, sizeof(mig)))
+ return -EFAULT;
+ return 0;
+}
+
static int kvm_s390_set_tod_high(struct kvm *kvm, struct kvm_device_attr *attr)
{
u8 gtod_high;
@@ -1090,6 +1214,9 @@ static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
case KVM_S390_VM_CRYPTO:
ret = kvm_s390_vm_set_crypto(kvm, attr);
break;
+ case KVM_S390_VM_MIGRATION:
+ ret = kvm_s390_vm_set_migration(kvm, attr);
+ break;
default:
ret = -ENXIO;
break;
@@ -1112,6 +1239,9 @@ static int kvm_s390_vm_get_attr(struct kvm *kvm, struct kvm_device_attr *attr)
case KVM_S390_VM_CPU_MODEL:
ret = kvm_s390_get_cpu_model(kvm, attr);
break;
+ case KVM_S390_VM_MIGRATION:
+ ret = kvm_s390_vm_get_migration(kvm, attr);
+ break;
default:
ret = -ENXIO;
break;
@@ -1179,6 +1309,9 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
break;
}
break;
+ case KVM_S390_VM_MIGRATION:
+ ret = 0;
+ break;
default:
ret = -ENXIO;
break;
@@ -1633,6 +1766,10 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
kvm_s390_destroy_adapters(kvm);
kvm_s390_clear_float_irqs(kvm);
kvm_s390_vsie_destroy(kvm);
+ if (kvm->arch.migration_state) {
+ vfree(kvm->arch.migration_state->pgste_bitmap);
+ kfree(kvm->arch.migration_state);
+ }
KVM_EVENT(3, "vm 0x%pK destroyed", kvm);
}

@@ -1977,7 +2114,6 @@ int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu)
if (!vcpu->arch.sie_block->cbrlo)
return -ENOMEM;

- vcpu->arch.sie_block->ecb2 |= ECB2_CMMA;
vcpu->arch.sie_block->ecb2 &= ~ECB2_PFMFI;
return 0;
}
@@ -2489,6 +2625,27 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
goto retry;
}

+ if (kvm_check_request(KVM_REQ_START_MIGRATION, vcpu)) {
+ /*
+ * Disable CMMA virtualization; we will emulate the ESSA
+ * instruction manually, in order to provide additional
+ * functionalities needed for live migration.
+ */
+ vcpu->arch.sie_block->ecb2 &= ~ECB2_CMMA;
+ goto retry;
+ }
+
+ if (kvm_check_request(KVM_REQ_STOP_MIGRATION, vcpu)) {
+ /*
+ * Re-enable CMMA virtualization if CMMA is available and
+ * was used.
+ */
+ if ((vcpu->kvm->arch.use_cmma) &&
+ (vcpu->kvm->mm->context.use_cmma))
+ vcpu->arch.sie_block->ecb2 |= ECB2_CMMA;
+ goto retry;
+ }
+
/* nothing to do, just clear the request */
kvm_clear_request(KVM_REQ_UNHALT, vcpu);

diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index c03106c..a226c45 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -24,6 +24,7 @@
#include <asm/ebcdic.h>
#include <asm/sysinfo.h>
#include <asm/pgtable.h>
+#include <asm/page-states.h>
#include <asm/pgalloc.h>
#include <asm/gmap.h>
#include <asm/io.h>
@@ -949,13 +950,72 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
return 0;
}

+static inline int do_essa(struct kvm_vcpu *vcpu, const int orc)
+{
+ struct kvm_s390_migration_state *ms = vcpu->kvm->arch.migration_state;
+ int r1, r2, nappended, entries;
+ unsigned long gfn, hva, res, pgstev, ptev;
+ unsigned long *cbrlo;
+
+ /*
+ * We don't need to set SD.FPF.SK to 1 here, because if we have a
+ * machine check here we either handle it or crash
+ */
+
+ kvm_s390_get_regs_rre(vcpu, &r1, &r2);
+ gfn = vcpu->run->s.regs.gprs[r2] >> PAGE_SHIFT;
+ hva = gfn_to_hva(vcpu->kvm, gfn);
+ entries = (vcpu->arch.sie_block->cbrlo & ~PAGE_MASK) >> 3;
+
+ if (kvm_is_error_hva(hva))
+ return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
+
+ nappended = pgste_perform_essa(vcpu->kvm->mm, hva, orc, &ptev, &pgstev);
+ if (nappended < 0) {
+ res = orc ? 0x10 : 0;
+ vcpu->run->s.regs.gprs[r1] = res; /* Exception Indication */
+ return 0;
+ }
+ res = (pgstev & _PGSTE_GPS_USAGE_MASK) >> 22;
+ /*
+ * Set the block-content state part of the result. 0 means resident, so
+ * nothing to do if the page is valid. 2 is for preserved pages
+ * (non-present and non-zero), and 3 for zero pages (non-present and
+ * zero).
+ */
+ if (ptev & _PAGE_INVALID) {
+ res |= 2;
+ if (pgstev & _PGSTE_GPS_ZERO)
+ res |= 1;
+ }
+ vcpu->run->s.regs.gprs[r1] = res;
+ /*
+ * It is possible that all the normal 511 slots were full, in which case
+ * we will now write in the 512th slot, which is reserved for host use.
+ * In both cases we let the normal essa handling code process all the
+ * slots, including the reserved one, if needed.
+ */
+ if (nappended > 0) {
+ cbrlo = phys_to_virt(vcpu->arch.sie_block->cbrlo & PAGE_MASK);
+ cbrlo[entries] = gfn << PAGE_SHIFT;
+ }
+
+ if (orc) {
+ /* increment only if we are really flipping the bit to 1 */
+ if (!test_and_set_bit(gfn, ms->pgste_bitmap))
+ atomic64_inc(&ms->dirty_pages);
+ }
+
+ return nappended;
+}
+
static int handle_essa(struct kvm_vcpu *vcpu)
{
/* entries expected to be 1FF */
int entries = (vcpu->arch.sie_block->cbrlo & ~PAGE_MASK) >> 3;
unsigned long *cbrlo;
struct gmap *gmap;
- int i;
+ int i, orc;

VCPU_EVENT(vcpu, 4, "ESSA: release %d pages", entries);
gmap = vcpu->arch.gmap;
@@ -965,12 +1025,45 @@ static int handle_essa(struct kvm_vcpu *vcpu)

if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
-
- if (((vcpu->arch.sie_block->ipb & 0xf0000000) >> 28) > 6)
+ /* Check for invalid operation request code */
+ orc = (vcpu->arch.sie_block->ipb & 0xf0000000) >> 28;
+ if (orc > ESSA_MAX)
return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);

- /* Retry the ESSA instruction */
- kvm_s390_retry_instr(vcpu);
+ if (likely(!vcpu->kvm->arch.migration_state)) {
+ /*
+ * CMMA is enabled in the KVM settings, but is disabled in
+ * the SIE block and in the mm_context, and we are not doing
+ * a migration. Enable CMMA in the mm_context.
+ * Since we need to take a write lock to write to the context
+ * to avoid races with storage keys handling, we check if the
+ * value really needs to be written to; if the value is
+ * already correct, we do nothing and avoid the lock.
+ */
+ if (vcpu->kvm->mm->context.use_cmma == 0) {
+ down_write(&vcpu->kvm->mm->mmap_sem);
+ vcpu->kvm->mm->context.use_cmma = 1;
+ up_write(&vcpu->kvm->mm->mmap_sem);
+ }
+ /*
+ * If we are here, we are supposed to have CMMA enabled in
+ * the SIE block. Enabling CMMA works on a per-CPU basis,
+ * while the context use_cmma flag is per process.
+ * It's possible that the context flag is enabled and the
+ * SIE flag is not, so we set the flag always; if it was
+ * already set, nothing changes, otherwise we enable it
+ * on this CPU too.
+ */
+ vcpu->arch.sie_block->ecb2 |= ECB2_CMMA;
+ /* Retry the ESSA instruction */
+ kvm_s390_retry_instr(vcpu);
+ } else {
+ /* Account for the possible extra cbrl entry */
+ i = do_essa(vcpu, orc);
+ if (i < 0)
+ return i;
+ entries += i;
+ }
vcpu->arch.sie_block->cbrlo &= PAGE_MASK; /* reset nceo */
cbrlo = phys_to_virt(vcpu->arch.sie_block->cbrlo);
down_read(&gmap->mm->mmap_sem);
--
2.7.4