[Qemu-devel] [PATCH 08/11] pseries: savevm support for pseries machine

[Anthony Liguori <aliguori@us.ibm.com>]

From: David Gibson <david@gibson.dropbear.id.au>

This adds the necessary pieces to implement savevm / migration for the
pseries machine.  The most complex part here is migrating the hash
table - for the paravirtualized pseries machine the guest's hash page
table is not stored within guest memory, but externally and the guest
accesses it via hypercalls.

This patch uses a hypervisor reserved bit of the HPTE as a dirty bit
(tracking changes to the HPTE itself, not the page it references).
This is used to implement a live migration style incremental save and
restore of the hash table contents.

Normally a hash table is 16MB but it can get bigger depending on how
much RAM the guest has. Due to its nature, updates to it are random so
the live migration style is used for it.

In addition it adds VMStateDescription information to save and restore
the (few) remaining pieces of state information needed by the pseries
machine.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

---
Changes:
2013/09/07:
* added a comment about HPT size and migration style choice
---
 hw/ppc/spapr.c         | 269 ++++++++++++++++++++++++++++++++++++++++++++++++-
 hw/ppc/spapr_hcall.c   |   8 +-
 include/hw/ppc/spapr.h |  12 ++-
 3 files changed, 281 insertions(+), 8 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e340708..734a782 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -32,6 +32,7 @@
 #include "sysemu/cpus.h"
 #include "sysemu/kvm.h"
 #include "kvm_ppc.h"
+#include "mmu-hash64.h"
 
 #include "hw/boards.h"
 #include "hw/ppc/ppc.h"
@@ -666,7 +667,7 @@ static void spapr_cpu_reset(void *opaque)
 
     env->spr[SPR_HIOR] = 0;
 
-    env->external_htab = spapr->htab;
+    env->external_htab = (uint8_t *)spapr->htab;
     env->htab_base = -1;
     env->htab_mask = HTAB_SIZE(spapr) - 1;
     env->spr[SPR_SDR1] = (target_ulong)(uintptr_t)spapr->htab |
@@ -710,6 +711,268 @@ static int spapr_vga_init(PCIBus *pci_bus)
     }
 }
 
+static const VMStateDescription vmstate_spapr = {
+    .name = "spapr",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .minimum_version_id_old = 1,
+    .fields      = (VMStateField []) {
+        VMSTATE_UINT32(next_irq, sPAPREnvironment),
+
+        /* RTC offset */
+        VMSTATE_UINT64(rtc_offset, sPAPREnvironment),
+
+        VMSTATE_END_OF_LIST()
+    },
+};
+
+#define HPTE(_table, _i)   (void *)(((uint64_t *)(_table)) + ((_i) * 2))
+#define HPTE_VALID(_hpte)  (tswap64(*((uint64_t *)(_hpte))) & HPTE64_V_VALID)
+#define HPTE_DIRTY(_hpte)  (tswap64(*((uint64_t *)(_hpte))) & HPTE64_V_HPTE_DIRTY)
+#define CLEAN_HPTE(_hpte)  ((*(uint64_t *)(_hpte)) &= tswap64(~HPTE64_V_HPTE_DIRTY))
+
+static int htab_save_setup(QEMUFile *f, void *opaque)
+{
+    sPAPREnvironment *spapr = opaque;
+
+    spapr->htab_save_index = 0;
+    spapr->htab_first_pass = true;
+
+    /* "Iteration" header */
+    qemu_put_be32(f, spapr->htab_shift);
+
+    return 0;
+}
+
+#define MAX_ITERATION_NS    5000000 /* 5 ms */
+
+static void htab_save_first_pass(QEMUFile *f, sPAPREnvironment *spapr,
+                                 int64_t max_ns)
+{
+    int htabslots = HTAB_SIZE(spapr) / HASH_PTE_SIZE_64;
+    int index = spapr->htab_save_index;
+    int64_t starttime = qemu_get_clock_ns(rt_clock);
+
+    assert(spapr->htab_first_pass);
+
+    do {
+        int chunkstart;
+
+        /* Consume invalid HPTEs */
+        while ((index < htabslots)
+               && !HPTE_VALID(HPTE(spapr->htab, index))) {
+            index++;
+            CLEAN_HPTE(HPTE(spapr->htab, index));
+        }
+
+        /* Consume valid HPTEs */
+        chunkstart = index;
+        while ((index < htabslots)
+               && HPTE_VALID(HPTE(spapr->htab, index))) {
+            index++;
+            CLEAN_HPTE(HPTE(spapr->htab, index));
+        }
+
+        if (index > chunkstart) {
+            int n_valid = index - chunkstart;
+
+            qemu_put_be32(f, chunkstart);
+            qemu_put_be16(f, n_valid);
+            qemu_put_be16(f, 0);
+            qemu_put_buffer(f, HPTE(spapr->htab, chunkstart),
+                            HASH_PTE_SIZE_64 * n_valid);
+
+            if ((qemu_get_clock_ns(rt_clock) - starttime) > max_ns) {
+                break;
+            }
+        }
+    } while ((index < htabslots) && !qemu_file_rate_limit(f));
+
+    if (index >= htabslots) {
+        assert(index == htabslots);
+        index = 0;
+        spapr->htab_first_pass = false;
+    }
+    spapr->htab_save_index = index;
+}
+
+static bool htab_save_later_pass(QEMUFile *f, sPAPREnvironment *spapr,
+                                 int64_t max_ns)
+{
+    bool final = max_ns < 0;
+    int htabslots = HTAB_SIZE(spapr) / HASH_PTE_SIZE_64;
+    int examined = 0, sent = 0;
+    int index = spapr->htab_save_index;
+    int64_t starttime = qemu_get_clock_ns(rt_clock);
+
+    assert(!spapr->htab_first_pass);
+
+    do {
+        int chunkstart, invalidstart;
+
+        /* Consume non-dirty HPTEs */
+        while ((index < htabslots)
+               && !HPTE_DIRTY(HPTE(spapr->htab, index))) {
+            index++;
+            examined++;
+        }
+
+        chunkstart = index;
+        /* Consume valid dirty HPTEs */
+        while ((index < htabslots)
+               && HPTE_DIRTY(HPTE(spapr->htab, index))
+               && HPTE_VALID(HPTE(spapr->htab, index))) {
+            CLEAN_HPTE(HPTE(spapr->htab, index));
+            index++;
+            examined++;
+        }
+
+        invalidstart = index;
+        /* Consume invalid dirty HPTEs */
+        while ((index < htabslots)
+               && HPTE_DIRTY(HPTE(spapr->htab, index))
+               && !HPTE_VALID(HPTE(spapr->htab, index))) {
+            CLEAN_HPTE(HPTE(spapr->htab, index));
+            index++;
+            examined++;
+        }
+
+        if (index > chunkstart) {
+            int n_valid = invalidstart - chunkstart;
+            int n_invalid = index - invalidstart;
+
+            qemu_put_be32(f, chunkstart);
+            qemu_put_be16(f, n_valid);
+            qemu_put_be16(f, n_invalid);
+            qemu_put_buffer(f, HPTE(spapr->htab, chunkstart),
+                            HASH_PTE_SIZE_64 * n_valid);
+            sent += index - chunkstart;
+
+            if (!final && (qemu_get_clock_ns(rt_clock) - starttime) > max_ns) {
+                break;
+            }
+        }
+
+        if (examined >= htabslots) {
+            break;
+        }
+
+        if (index >= htabslots) {
+            assert(index == htabslots);
+            index = 0;
+        }
+    } while ((examined < htabslots) && (!qemu_file_rate_limit(f) || final));
+
+    if (index >= htabslots) {
+        assert(index == htabslots);
+        index = 0;
+    }
+
+    spapr->htab_save_index = index;
+
+    return (examined >= htabslots) && (sent == 0);
+}
+
+static int htab_save_iterate(QEMUFile *f, void *opaque)
+{
+    sPAPREnvironment *spapr = opaque;
+    bool nothingleft = false;;
+
+    /* Iteration header */
+    qemu_put_be32(f, 0);
+
+    if (spapr->htab_first_pass) {
+        htab_save_first_pass(f, spapr, MAX_ITERATION_NS);
+    } else {
+        nothingleft = htab_save_later_pass(f, spapr, MAX_ITERATION_NS);
+    }
+
+    /* End marker */
+    qemu_put_be32(f, 0);
+    qemu_put_be16(f, 0);
+    qemu_put_be16(f, 0);
+
+    return nothingleft ? 1 : 0;
+}
+
+static int htab_save_complete(QEMUFile *f, void *opaque)
+{
+    sPAPREnvironment *spapr = opaque;
+
+    /* Iteration header */
+    qemu_put_be32(f, 0);
+
+    htab_save_later_pass(f, spapr, -1);
+
+    /* End marker */
+    qemu_put_be32(f, 0);
+    qemu_put_be16(f, 0);
+    qemu_put_be16(f, 0);
+
+    return 0;
+}
+
+static int htab_load(QEMUFile *f, void *opaque, int version_id)
+{
+    sPAPREnvironment *spapr = opaque;
+    uint32_t section_hdr;
+
+    if (version_id < 1 || version_id > 1) {
+        fprintf(stderr, "htab_load() bad version\n");
+        return -EINVAL;
+    }
+
+    section_hdr = qemu_get_be32(f);
+
+    if (section_hdr) {
+        /* First section, just the hash shift */
+        if (spapr->htab_shift != section_hdr) {
+            return -EINVAL;
+        }
+        return 0;
+    }
+
+    while (true) {
+        uint32_t index;
+        uint16_t n_valid, n_invalid;
+
+        index = qemu_get_be32(f);
+        n_valid = qemu_get_be16(f);
+        n_invalid = qemu_get_be16(f);
+
+        if ((index == 0) && (n_valid == 0) && (n_invalid == 0)) {
+            /* End of Stream */
+            break;
+        }
+
+        if ((index + n_valid + n_invalid) >=
+            (HTAB_SIZE(spapr) / HASH_PTE_SIZE_64)) {
+            /* Bad index in stream */
+            fprintf(stderr, "htab_load() bad index %d (%hd+%hd entries) "
+                    "in htab stream\n", index, n_valid, n_invalid);
+            return -EINVAL;
+        }
+
+        if (n_valid) {
+            qemu_get_buffer(f, HPTE(spapr->htab, index),
+                            HASH_PTE_SIZE_64 * n_valid);
+        }
+        if (n_invalid) {
+            memset(HPTE(spapr->htab, index + n_valid), 0,
+                   HASH_PTE_SIZE_64 * n_invalid);
+        }
+    }
+
+    return 0;
+}
+
+static SaveVMHandlers savevm_htab_handlers = {
+    .save_live_setup = htab_save_setup,
+    .save_live_iterate = htab_save_iterate,
+    .save_live_complete = htab_save_complete,
+    .load_state = htab_load,
+};
+
 /* pSeries LPAR / sPAPR hardware init */
 static void ppc_spapr_init(QEMUMachineInitArgs *args)
 {
@@ -950,6 +1213,10 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
 
     spapr->entry_point = 0x100;
 
+    vmstate_register(NULL, 0, &vmstate_spapr, spapr);
+    register_savevm_live(NULL, "spapr/htab", -1, 1,
+                         &savevm_htab_handlers, spapr);
+
     /* Prepare the device tree */
     spapr->fdt_skel = spapr_create_fdt_skel(cpu_model,
                                             initrd_base, initrd_size,
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index ed32dec..67d6cd9 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -115,7 +115,7 @@ static target_ulong h_enter(PowerPCCPU *cpu, sPAPREnvironment *spapr,
     }
     ppc_hash64_store_hpte1(env, hpte, ptel);
     /* eieio();  FIXME: need some sort of barrier for smp? */
-    ppc_hash64_store_hpte0(env, hpte, pteh);
+    ppc_hash64_store_hpte0(env, hpte, pteh | HPTE64_V_HPTE_DIRTY);
 
     args[0] = pte_index + i;
     return H_SUCCESS;
@@ -152,7 +152,7 @@ static RemoveResult remove_hpte(CPUPPCState *env, target_ulong ptex,
     }
     *vp = v;
     *rp = r;
-    ppc_hash64_store_hpte0(env, hpte, 0);
+    ppc_hash64_store_hpte0(env, hpte, HPTE64_V_HPTE_DIRTY);
     rb = compute_tlbie_rb(v, r, ptex);
     ppc_tlb_invalidate_one(env, rb);
     return REMOVE_SUCCESS;
@@ -282,11 +282,11 @@ static target_ulong h_protect(PowerPCCPU *cpu, sPAPREnvironment *spapr,
     r |= (flags << 48) & HPTE64_R_KEY_HI;
     r |= flags & (HPTE64_R_PP | HPTE64_R_N | HPTE64_R_KEY_LO);
     rb = compute_tlbie_rb(v, r, pte_index);
-    ppc_hash64_store_hpte0(env, hpte, v & ~HPTE64_V_VALID);
+    ppc_hash64_store_hpte0(env, hpte, (v & ~HPTE64_V_VALID) | HPTE64_V_HPTE_DIRTY);
     ppc_tlb_invalidate_one(env, rb);
     ppc_hash64_store_hpte1(env, hpte, r);
     /* Don't need a memory barrier, due to qemu's global lock */
-    ppc_hash64_store_hpte0(env, hpte, v);
+    ppc_hash64_store_hpte0(env, hpte, v | HPTE64_V_HPTE_DIRTY);
     return H_SUCCESS;
 }
 
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 82ad7c0..00a6f58 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -9,6 +9,8 @@ struct sPAPRPHBState;
 struct sPAPRNVRAM;
 struct icp_state;
 
+#define HPTE64_V_HPTE_DIRTY     0x0000000000000040ULL
+
 typedef struct sPAPREnvironment {
     struct VIOsPAPRBus *vio_bus;
     QLIST_HEAD(, sPAPRPHBState) phbs;
@@ -17,20 +19,24 @@ typedef struct sPAPREnvironment {
 
     hwaddr ram_limit;
     void *htab;
-    long htab_shift;
+    uint32_t htab_shift;
     hwaddr rma_size;
     int vrma_adjust;
     hwaddr fdt_addr, rtas_addr;
     long rtas_size;
     void *fdt_skel;
     target_ulong entry_point;
-    int next_irq;
-    int rtc_offset;
+    uint32_t next_irq;
+    uint64_t rtc_offset;
     char *cpu_model;
     bool has_graphics;
 
     uint32_t epow_irq;
     Notifier epow_notifier;
+
+    /* Migration state */
+    int htab_save_index;
+    bool htab_first_pass;
 } sPAPREnvironment;
 
 #define H_SUCCESS         0
-- 
1.8.0