[PATCH 2/2] s390/kvm: support collaborative memory management
From: Martin Schwidefsky
Date: Wed Jul 03 2013 - 09:02:37 EST
From: Konstantin Weitz <konstantin.weitz@xxxxxxxxx>
This patch enables Collaborative Memory Management (CMM) for kvm
on s390. CMM allows the guest to inform the host about page usage
(see arch/s390/mm/cmm.c). The host uses this information to avoid
swapping in unused pages in the page fault handler. Further, a CPU
provided list of unused invalid pages is processed to reclaim swap
space of not yet accessed unused pages.
[ Martin Schwidefsky: patch reordering and cleanup ]
Signed-off-by: Konstantin Weitz <konstantin.weitz@xxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
arch/s390/include/asm/kvm_host.h | 8 +++-
arch/s390/include/asm/pgtable.h | 24 ++++++++++++
arch/s390/kvm/kvm-s390.c | 24 ++++++++++++
arch/s390/kvm/kvm-s390.h | 2 +
arch/s390/kvm/priv.c | 37 ++++++++++++++++++
arch/s390/mm/pgtable.c | 77 ++++++++++++++++++++++++++++++++++++++
mm/rmap.c | 2 +-
7 files changed, 171 insertions(+), 3 deletions(-)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 16bd5d1..8d1bcf4 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -90,7 +90,8 @@ struct kvm_s390_sie_block {
__u32 scaoh; /* 0x005c */
__u8 reserved60; /* 0x0060 */
__u8 ecb; /* 0x0061 */
- __u8 reserved62[2]; /* 0x0062 */
+ __u8 ecb2; /* 0x0062 */
+ __u8 reserved63[1]; /* 0x0063 */
__u32 scaol; /* 0x0064 */
__u8 reserved68[4]; /* 0x0068 */
__u32 todpr; /* 0x006c */
@@ -105,7 +106,9 @@ struct kvm_s390_sie_block {
__u64 gbea; /* 0x0180 */
__u8 reserved188[24]; /* 0x0188 */
__u32 fac; /* 0x01a0 */
- __u8 reserved1a4[92]; /* 0x01a4 */
+ __u8 reserved1a4[20]; /* 0x01a4 */
+ __u64 cbrlo; /* 0x01b8 */
+ __u8 reserved1c0[64]; /* 0x01c0 */
} __attribute__((packed));
struct kvm_vcpu_stat {
@@ -140,6 +143,7 @@ struct kvm_vcpu_stat {
u32 instruction_stsi;
u32 instruction_stfl;
u32 instruction_tprot;
+ u32 instruction_essa;
u32 instruction_sigp_sense;
u32 instruction_sigp_sense_running;
u32 instruction_sigp_external_call;
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 9aefa3c..061e274 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -227,6 +227,7 @@ extern unsigned long MODULES_END;
#define _PAGE_SWR 0x008 /* SW pte referenced bit */
#define _PAGE_SWW 0x010 /* SW pte write bit */
#define _PAGE_SPECIAL 0x020 /* SW associated with special page */
+#define _PAGE_UNUSED 0x040 /* SW bit for ptep_clear_flush() */
#define __HAVE_ARCH_PTE_SPECIAL
/* Set of bits not changed in pte_modify */
@@ -379,6 +380,12 @@ extern unsigned long MODULES_END;
#endif /* CONFIG_64BIT */
+/* Guest Page State used for virtualization */
+#define _PGSTE_GPS_ZERO 0x0000000080000000UL
+#define _PGSTE_GPS_USAGE_MASK 0x0000000003000000UL
+#define _PGSTE_GPS_USAGE_STABLE 0x0000000000000000UL
+#define _PGSTE_GPS_USAGE_UNUSED 0x0000000001000000UL
+
/*
* A user page table pointer has the space-switch-event bit, the
* private-space-control bit and the storage-alteration-event-control
@@ -594,6 +601,12 @@ static inline int pte_file(pte_t pte)
return (pte_val(pte) & mask) == _PAGE_TYPE_FILE;
}
+static inline int pte_swap(pte_t pte)
+{
+ unsigned long mask = _PAGE_RO | _PAGE_INVALID | _PAGE_SWT | _PAGE_SWX;
+ return (pte_val(pte) & mask) == _PAGE_TYPE_SWAP;
+}
+
static inline int pte_special(pte_t pte)
{
return (pte_val(pte) & _PAGE_SPECIAL);
@@ -797,6 +810,7 @@ unsigned long gmap_translate(unsigned long address, struct gmap *);
unsigned long __gmap_fault(unsigned long address, struct gmap *);
unsigned long gmap_fault(unsigned long address, struct gmap *);
void gmap_discard(unsigned long from, unsigned long to, struct gmap *);
+void __gmap_zap(unsigned long address, struct gmap *);
void gmap_register_ipte_notifier(struct gmap_notifier *);
void gmap_unregister_ipte_notifier(struct gmap_notifier *);
@@ -828,6 +842,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
if (mm_has_pgste(mm)) {
pgste = pgste_get_lock(ptep);
+ pgste_val(pgste) &= ~_PGSTE_GPS_ZERO;
pgste_set_key(ptep, pgste, entry);
pgste_set_pte(ptep, entry);
pgste_set_unlock(ptep, pgste);
@@ -861,6 +876,12 @@ static inline int pte_young(pte_t pte)
return 0;
}
+#define __HAVE_ARCH_PTE_UNUSED
+static inline int pte_unused(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_UNUSED;
+}
+
/*
* pgd/pmd/pte modification functions
*/
@@ -1145,6 +1166,9 @@ static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
pte_val(*ptep) = _PAGE_TYPE_EMPTY;
if (mm_has_pgste(vma->vm_mm)) {
+ if ((pgste_val(pgste) & _PGSTE_GPS_USAGE_MASK) ==
+ _PGSTE_GPS_USAGE_UNUSED)
+ pte_val(pte) |= _PAGE_UNUSED;
pgste = pgste_update_all(&pte, pgste);
pgste_set_unlock(ptep, pgste);
}
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c1c7c68..4961845 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -66,6 +66,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "instruction_storage_key", VCPU_STAT(instruction_storage_key) },
{ "instruction_stsch", VCPU_STAT(instruction_stsch) },
{ "instruction_chsc", VCPU_STAT(instruction_chsc) },
+ { "instruction_essa", VCPU_STAT(instruction_essa) },
{ "instruction_stsi", VCPU_STAT(instruction_stsi) },
{ "instruction_stfl", VCPU_STAT(instruction_stfl) },
{ "instruction_tprot", VCPU_STAT(instruction_tprot) },
@@ -268,7 +269,11 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
if (kvm_is_ucontrol(vcpu->kvm))
gmap_free(vcpu->arch.gmap);
+ if (vcpu->arch.sie_block->cbrlo)
+ __free_page(__pfn_to_page(
+ vcpu->arch.sie_block->cbrlo >> PAGE_SHIFT));
free_page((unsigned long)(vcpu->arch.sie_block));
+
kvm_vcpu_uninit(vcpu);
kfree(vcpu);
}
@@ -371,12 +376,21 @@ int kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
{
+ struct page *cbrl;
+
atomic_set(&vcpu->arch.sie_block->cpuflags, CPUSTAT_ZARCH |
CPUSTAT_SM |
CPUSTAT_STOPPED);
vcpu->arch.sie_block->ecb = 6;
vcpu->arch.sie_block->eca = 0xC1002001U;
vcpu->arch.sie_block->fac = (int) (long) facilities;
+ if (kvm_enabled_cmma()) {
+ cbrl = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (cbrl) {
+ vcpu->arch.sie_block->ecb2 = 0x80;
+ vcpu->arch.sie_block->cbrlo = page_to_phys(cbrl);
+ }
+ }
hrtimer_init(&vcpu->arch.ckc_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
tasklet_init(&vcpu->arch.tasklet, kvm_s390_tasklet,
(unsigned long) vcpu);
@@ -606,6 +620,16 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
return -EINVAL; /* not implemented yet */
}
+bool kvm_enabled_cmma(void)
+{
+ if (!MACHINE_IS_LPAR)
+ return false;
+ /* only enable for z10 and later */
+ if (!MACHINE_HAS_EDAT1)
+ return false;
+ return true;
+}
+
static int __vcpu_run(struct kvm_vcpu *vcpu)
{
int rc;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index efc14f6..9caf102 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -133,6 +133,8 @@ int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu);
/* implemented in kvm-s390.c */
int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu,
unsigned long addr);
+/* are we going to support cmma? */
+bool kvm_enabled_cmma(void);
/* implemented in diag.c */
int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 6bbd7b5..ddccf39 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -20,6 +20,8 @@
#include <asm/debug.h>
#include <asm/ebcdic.h>
#include <asm/sysinfo.h>
+#include <asm/pgtable.h>
+#include <asm/io.h>
#include <asm/ptrace.h>
#include <asm/compat.h>
#include "gaccess.h"
@@ -467,9 +469,44 @@ static int handle_epsw(struct kvm_vcpu *vcpu)
return 0;
}
+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, cbrle;
+ struct gmap *gmap;
+ int i;
+
+ VCPU_EVENT(vcpu, 5, "cmma release %d pages", entries);
+ gmap = vcpu->arch.gmap;
+ vcpu->stat.instruction_essa++;
+ if (!kvm_enabled_cmma() || !vcpu->arch.sie_block->cbrlo)
+ return kvm_s390_inject_program_int(vcpu, PGM_OPERATION);
+
+ /* Rewind PSW to repeat the ESSA instruction */
+ vcpu->arch.sie_block->gpsw.addr =
+ __rewind_psw(vcpu->arch.sie_block->gpsw, 4);
+ vcpu->arch.sie_block->cbrlo &= PAGE_MASK; /* reset nceo */
+ cbrlo = phys_to_virt(vcpu->arch.sie_block->cbrlo);
+ down_read(&gmap->mm->mmap_sem);
+ for (i = 0; i < entries; ++i) {
+ cbrle = cbrlo[i];
+ if (unlikely(cbrle & ~PAGE_MASK || cbrle < 2 * PAGE_SIZE))
+ /* invalid entry */
+ break;
+ /* try to free backing */
+ __gmap_zap(cbrle, gmap);
+ }
+ up_read(&gmap->mm->mmap_sem);
+ if (i < entries)
+ return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
+ return 0;
+}
+
static const intercept_handler_t b9_handlers[256] = {
[0x8d] = handle_epsw,
[0x9c] = handle_io_inst,
+ [0xab] = handle_essa,
};
int kvm_s390_handle_b9(struct kvm_vcpu *vcpu)
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index a938b54..5a4d8ef 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -17,6 +17,7 @@
#include <linux/quicklist.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
+#include <linux/swapops.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -573,6 +574,82 @@ unsigned long gmap_fault(unsigned long address, struct gmap *gmap)
}
EXPORT_SYMBOL_GPL(gmap_fault);
+static void gmap_zap_swap_entry(swp_entry_t entry, struct mm_struct *mm)
+{
+ if (!non_swap_entry(entry))
+ dec_mm_counter(mm, MM_SWAPENTS);
+ else if (is_migration_entry(entry)) {
+ struct page *page = migration_entry_to_page(entry);
+
+ if (PageAnon(page))
+ dec_mm_counter(mm, MM_ANONPAGES);
+ else
+ dec_mm_counter(mm, MM_FILEPAGES);
+ }
+ free_swap_and_cache(entry);
+}
+
+/**
+ * The mm->mmap_sem lock must be held
+ */
+static void gmap_zap_unused(struct mm_struct *mm, unsigned long address)
+{
+ unsigned long ptev, pgstev;
+ spinlock_t *ptl;
+ pgste_t pgste;
+ pte_t *ptep, pte;
+
+ ptep = get_locked_pte(mm, address, &ptl);
+ if (unlikely(!ptep))
+ return;
+ pte = *ptep;
+ if (!pte_swap(pte))
+ goto out_pte;
+ /* Zap unused and logically-zero pages */
+ pgste = pgste_get_lock(ptep);
+ pgstev = pgste_val(pgste);
+ ptev = pte_val(pte);
+ if (((pgstev & _PGSTE_GPS_USAGE_MASK) == _PGSTE_GPS_USAGE_UNUSED) ||
+ ((pgstev & _PGSTE_GPS_ZERO) && (ptev & _PAGE_INVALID))) {
+ gmap_zap_swap_entry(pte_to_swp_entry(pte), mm);
+ pte_clear(mm, address, ptep);
+ }
+ pgste_set_unlock(ptep, pgste);
+out_pte:
+ pte_unmap_unlock(*ptep, ptl);
+}
+
+/*
+ * this function is assumed to be called with mmap_sem held
+ */
+void __gmap_zap(unsigned long address, struct gmap *gmap)
+{
+ unsigned long *table, *segment_ptr;
+ unsigned long segment, pgstev, ptev;
+ struct gmap_pgtable *mp;
+ struct page *page;
+
+ segment_ptr = gmap_table_walk(address, gmap);
+ if (IS_ERR(segment_ptr))
+ return;
+ segment = *segment_ptr;
+ if (segment & _SEGMENT_ENTRY_INV)
+ return;
+ page = pfn_to_page(segment >> PAGE_SHIFT);
+ mp = (struct gmap_pgtable *) page->index;
+ address = mp->vmaddr | (address & ~PMD_MASK);
+ /* Page table is present */
+ table = (unsigned long *)(segment & _SEGMENT_ENTRY_ORIGIN);
+ table = table + ((address >> 12) & 0xff);
+ pgstev = table[PTRS_PER_PTE];
+ ptev = table[0];
+ /* quick check, checked again with locks held */
+ if (((pgstev & _PGSTE_GPS_USAGE_MASK) == _PGSTE_GPS_USAGE_UNUSED) ||
+ ((pgstev & _PGSTE_GPS_ZERO) && (ptev & _PAGE_INVALID)))
+ gmap_zap_unused(gmap->mm, address);
+}
+EXPORT_SYMBOL_GPL(__gmap_zap);
+
void gmap_discard(unsigned long from, unsigned long to, struct gmap *gmap)
{
diff --git a/mm/rmap.c b/mm/rmap.c
index be2788d..3155097 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1233,7 +1233,7 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
}
set_pte_at(mm, address, pte,
swp_entry_to_pte(make_hwpoison_entry(page)));
- } else if (pte_unused(pteval) && PageAnon(page)) {
+ } else if (pte_unused(pteval) && PageSwapCache(page) && PageAnon(page)) {
pte_clear(mm, address, pte);
dec_mm_counter(mm, MM_ANONPAGES);
ret = SWAP_FREE;
--
1.7.9.5
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