On Fri, Dec 09, 2016 at 09:36:17AM +0100, Thomas Huth wrote: > On 09.12.2016 03:23, David Gibson wrote: > > This patch implements hypercalls allowing a PAPR guest to resize its own > > hash page table. This will eventually allow for more flexible memory > > hotplug. > > > > The implementation is partially asynchronous, handled in a special thread > > running the hpt_prepare_thread() function. The state of a pending resize > > is stored in SPAPR_MACHINE->pending_hpt. > > > > The H_RESIZE_HPT_PREPARE hypercall will kick off creation of a new HPT, or, > > if one is already in progress, monitor it for completion. If there is an > > existing HPT resize in progress that doesn't match the size specified in > > the call, it will cancel it, replacing it with a new one matching the > > given size. > > > > The H_RESIZE_HPT_COMMIT completes transition to a resized HPT, and can only > > be called successfully once H_RESIZE_HPT_PREPARE has successfully > > completed initialization of a new HPT. The guest must ensure that there > > are no concurrent accesses to the existing HPT while this is called (this > > effectively means stop_machine() for Linux guests). > > > > For now H_RESIZE_HPT_COMMIT goes through the whole old HPT, rehashing each > > HPTE into the new HPT. This can have quite high latency, but it seems to > > be of the order of typical migration downtime latencies for HPTs of size > > up to ~2GiB (which would be used in a 256GiB guest). > > > > In future we probably want to move more of the rehashing to the "prepare" > > phase, by having H_ENTER and other hcalls update both current and > > pending HPTs. That's a project for another day, but should be possible > > without any changes to the guest interface. > > > > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> > > --- > > hw/ppc/spapr.c | 4 +- > > hw/ppc/spapr_hcall.c | 346 > > +++++++++++++++++++++++++++++++++++++++++++++++- > > I wonder whether it makes sense to put all the hpt related code into a > separate new file?
Maybe, but not really in scope here. > > include/hw/ppc/spapr.h | 6 + > > target-ppc/mmu-hash64.h | 4 + > > 4 files changed, 354 insertions(+), 6 deletions(-) > > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > > index ecb0822..f3b74dc 100644 > > --- a/hw/ppc/spapr.c > > +++ b/hw/ppc/spapr.c > > @@ -93,8 +93,6 @@ > > > > #define PHANDLE_XICP 0x00001111 > > > > -#define HTAB_SIZE(spapr) (1ULL << ((spapr)->htab_shift)) > > - > > static XICSState *try_create_xics(const char *type, int nr_servers, > > int nr_irqs, Error **errp) > > { > > @@ -1055,7 +1053,7 @@ static void close_htab_fd(sPAPRMachineState *spapr) > > spapr->htab_fd = -1; > > } > > > > -static int spapr_hpt_shift_for_ramsize(uint64_t ramsize) > > +int spapr_hpt_shift_for_ramsize(uint64_t ramsize) > > { > > int shift; > > > > diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c > > index 72a9c4d..9f421c1 100644 > > --- a/hw/ppc/spapr_hcall.c > > +++ b/hw/ppc/spapr_hcall.c > > @@ -2,6 +2,7 @@ > > #include "qapi/error.h" > > #include "sysemu/sysemu.h" > > #include "qemu/log.h" > > +#include "qemu/error-report.h" > > #include "cpu.h" > > #include "exec/exec-all.h" > > #include "helper_regs.h" > > @@ -355,20 +356,320 @@ static target_ulong h_read(PowerPCCPU *cpu, > > sPAPRMachineState *spapr, > > return H_SUCCESS; > > } > > > > +struct sPAPRPendingHPT { > > + /* These fields are read-only after initialization */ > > + int shift; > > + QemuThread thread; > > + > > + /* These fields are protected by the BQL */ > > + bool complete; > > + > > + /* These fields are private to the preparation thread if > > + * !complete, otherwise protected by the BQL */ > > + int ret; > > + void *hpt; > > +}; > > + > > +static void free_pending_hpt(sPAPRPendingHPT *pending) > > +{ > > + if (pending->hpt) { > > + qemu_vfree(pending->hpt); > > + } > > + > > + g_free(pending); > > +} > > + > > +static void *hpt_prepare_thread(void *opaque) > > +{ > > + sPAPRPendingHPT *pending = opaque; > > + size_t size = 1ULL << pending->shift; > > + > > + pending->hpt = qemu_memalign(size, size); > > + if (pending->hpt) { > > + memset(pending->hpt, 0, size); > > + pending->ret = H_SUCCESS; > > + } else { > > + pending->ret = H_NO_MEM; > > + } > > + > > + qemu_mutex_lock_iothread(); > > + > > + if (SPAPR_MACHINE(qdev_get_machine())->pending_hpt != pending) { > > + /* We've been cancelled, clean ourselves up */ > > + free_pending_hpt(pending); > > + goto out; > > + } > > + > > + pending->complete = true; > > + > > +out: > > You could easily avoid the goto here: > > if (SPAPR_MACHINE(qdev_get_machine())->pending_hpt != pending) { > /* We've been cancelled, clean ourselves up */ > free_pending_hpt(pending); > } else { > pending->complete = true; > } > > ? Ah, yeah, I guess so. I think I had more cases that used the same bailout path during development. > > + qemu_mutex_unlock_iothread(); > > + return NULL; > > +} > > + > > +/* Must be called with BQL held */ > > +static void cancel_hpt_prepare(sPAPRMachineState *spapr) > > +{ > > + sPAPRPendingHPT *pending = spapr->pending_hpt; > > + > > + /* Let the thread know it's cancelled */ > > + spapr->pending_hpt = NULL; > > + > > + if (!pending) { > > + /* Nothing to do */ > > + return; > > + } > > + > > + if (!pending->complete) { > > + /* thread will clean itself up */ > > + return; > > + } > > + > > + free_pending_hpt(pending); > > +} > > + > > +static int build_dimm_list(Object *obj, void *opaque) > > +{ > > + GSList **list = opaque; > > + > > + if (object_dynamic_cast(obj, TYPE_PC_DIMM)) { > > + DeviceState *dev = DEVICE(obj); > > + if (dev->realized) { /* only realized DIMMs matter */ > > + *list = g_slist_prepend(*list, dev); > > + } > > + } > > + > > + object_child_foreach(obj, build_dimm_list, opaque); > > + return 0; > > +} > > + > > +static ram_addr_t get_current_ram_size(void) > > +{ > > + GSList *list = NULL, *item; > > + ram_addr_t size = ram_size; > > + > > + build_dimm_list(qdev_get_machine(), &list); > > + for (item = list; item; item = g_slist_next(item)) { > > + Object *obj = OBJECT(item->data); > > + if (!strcmp(object_get_typename(obj), TYPE_PC_DIMM)) { > > + size += object_property_get_int(obj, PC_DIMM_SIZE_PROP, > > + &error_abort); > > + } > > + } > > + g_slist_free(list); > > + > > + return size; > > +} > > + > > static target_ulong h_resize_hpt_prepare(PowerPCCPU *cpu, > > sPAPRMachineState *spapr, > > target_ulong opcode, > > target_ulong *args) > > { > > target_ulong flags = args[0]; > > - target_ulong shift = args[1]; > > + int shift = args[1]; > > + sPAPRPendingHPT *pending = spapr->pending_hpt; > > > > if (spapr->resize_hpt == SPAPR_RESIZE_HPT_DISABLED) { > > return H_AUTHORITY; > > } > > > > trace_spapr_h_resize_hpt_prepare(flags, shift); > > - return H_HARDWARE; > > + > > + if (flags != 0) { > > + return H_PARAMETER; > > + } > > + > > + if (shift && ((shift < 18) || (shift > 46))) { > > + return H_PARAMETER; > > + } > > + > > + if (pending) { > > + /* something already in progress */ > > + if (pending->shift == shift) { > > + /* and it's suitable */ > > + if (pending->complete) { > > + return pending->ret; > > + } else { > > + return H_LONG_BUSY_ORDER_100_MSEC; > > + } > > + } > > + > > + /* not suitable, cancel and replace */ > > + cancel_hpt_prepare(spapr); > > + } > > + > > + if (!shift) { > > + /* nothing to do */ > > + return H_SUCCESS; > > + } > > + > > + /* start new prepare */ > > + > > + /* We only allow the guest to allocate an HPT one order above what > > + * we'd normally give them (to stop a small guest claiming a huge > > + * chunk of resources in the HPT */ > > + if (shift > (spapr_hpt_shift_for_ramsize(get_current_ram_size()) + 1)) > > { > > + return H_RESOURCE; > > + } > > + > > + pending = g_malloc0(sizeof(*pending)); > > Maybe use g_new0() instead? Ah, good idea. > > + pending->shift = shift; > > + pending->ret = H_HARDWARE; > > + > > + qemu_thread_create(&pending->thread, "sPAPR HPT prepare", > > + hpt_prepare_thread, pending, QEMU_THREAD_DETACHED); > > + > > + spapr->pending_hpt = pending; > > + > > + /* In theory we could estimate the time more accurately based on > > + * the new size, but there's not much point */ > > + return H_LONG_BUSY_ORDER_100_MSEC; > > +} > > + > > +static uint64_t new_hpte_load0(void *htab, uint64_t pteg, int slot) > > +{ > > + uint8_t *addr = htab; > > + > > + addr += pteg * HASH_PTEG_SIZE_64; > > + addr += slot * HASH_PTE_SIZE_64; > > + return ldq_p(addr); > > +} > > + > > +static void new_hpte_store(void *htab, uint64_t pteg, int slot, > > + uint64_t pte0, uint64_t pte1) > > +{ > > + uint8_t *addr = htab; > > + > > + addr += pteg * HASH_PTEG_SIZE_64; > > + addr += slot * HASH_PTE_SIZE_64; > > + > > + stq_p(addr, pte0); > > + stq_p(addr + HASH_PTE_SIZE_64/2, pte1); > > +} > > + > > +static int rehash_hpte(PowerPCCPU *cpu, uint64_t token, > > + void *old, uint64_t oldsize, > > + void *new, uint64_t newsize, > > + uint64_t pteg, int slot) > > +{ > > + uint64_t old_hash_mask = (oldsize >> 7) - 1; > > + uint64_t new_hash_mask = (newsize >> 7) - 1; > > + target_ulong pte0 = ppc_hash64_load_hpte0(cpu, token, slot); > > + target_ulong pte1; > > + uint64_t avpn; > > + unsigned shift; > > + uint64_t hash, new_pteg, replace_pte0; > > + > > + if (!(pte0 & HPTE64_V_VALID) || !(pte0 & HPTE64_V_BOLTED)) { > > + return H_SUCCESS; > > + } > > + > > + pte1 = ppc_hash64_load_hpte1(cpu, token, slot); > > + > > + shift = ppc_hash64_hpte_page_shift_noslb(cpu, pte0, pte1); > > + assert(shift); /* H_ENTER should never have allowed a bad encoding */ > > + avpn = HPTE64_V_AVPN_VAL(pte0) & ~(((1ULL << shift) - 1) >> 23); > > + > > + if (pte0 & HPTE64_V_SECONDARY) { > > + pteg = ~pteg; > > + } > > + > > + if ((pte0 & HPTE64_V_SSIZE) == HPTE64_V_SSIZE_256M) { > > + uint64_t offset, vsid; > > + > > + /* We only have 28 - 23 bits of offset in avpn */ > > + offset = (avpn & 0x1f) << 23; > > + vsid = avpn >> 5; > > + /* We can find more bits from the pteg value */ > > + if (shift < 23) { > > + offset |= ((vsid ^ pteg) & old_hash_mask) << shift; > > + } > > + > > + hash = vsid ^ (offset >> shift); > > + } else if ((pte0 & HPTE64_V_SSIZE) == HPTE64_V_SSIZE_1T) { > > + uint64_t offset, vsid; > > + > > + /* We only have 40 - 23 bits of seg_off in avpn */ > > + offset = (avpn & 0x1ffff) << 23; > > + vsid = avpn >> 17; > > + if (shift < 23) { > > + offset |= ((vsid ^ (vsid << 25) ^ pteg) & old_hash_mask) << > > shift; > > + } > > + > > + hash = vsid ^ (vsid << 25) ^ (offset >> shift); > > + } else { > > + error_report("rehash_pte: Bad segment size in HPTE"); > > + return H_HARDWARE; > > + } > > + > > + new_pteg = hash & new_hash_mask; > > + if (pte0 & HPTE64_V_SECONDARY) { > > + assert(~pteg == (hash & old_hash_mask)); > > + new_pteg = ~new_pteg; > > + } else { > > + assert(pteg == (hash & old_hash_mask)); > > + } > > + assert((oldsize != newsize) || (pteg == new_pteg)); > > + replace_pte0 = new_hpte_load0(new, new_pteg, slot); > > + if (replace_pte0 & HPTE64_V_VALID) { > > + assert(newsize < oldsize); > > + if (replace_pte0 & HPTE64_V_BOLTED) { > > + if (pte0 & HPTE64_V_BOLTED) { > > + /* Bolted collision, nothing we can do */ > > + return H_PTEG_FULL; > > + } else { > > + /* Discard this hpte */ > > + return H_SUCCESS; > > + } > > + } > > + } > > + > > + new_hpte_store(new, new_pteg, slot, pte0, pte1); > > + return H_SUCCESS; > > +} > > + > > +static int rehash_hpt(PowerPCCPU *cpu, > > + void *old, uint64_t oldsize, > > + void *new, uint64_t newsize) > > +{ > > + CPUPPCState *env = &cpu->env; > > + uint64_t n_ptegs = oldsize >> 7; > > + uint64_t pteg; > > + int slot; > > + int rc; > > + > > + assert(env->external_htab == old); > > + > > + for (pteg = 0; pteg < n_ptegs; pteg++) { > > + uint64_t token = ppc_hash64_start_access(cpu, pteg * > > HPTES_PER_GROUP); > > + > > + if (!token) { > > + return H_HARDWARE; > > + } > > + > > + for (slot = 0; slot < HPTES_PER_GROUP; slot++) { > > + rc = rehash_hpte(cpu, token, old, oldsize, new, newsize, > > + pteg, slot); > > + if (rc != H_SUCCESS) { > > + ppc_hash64_stop_access(cpu, token); > > + return rc; > > + } > > + } > > + ppc_hash64_stop_access(cpu, token); > > + } > > + > > + return H_SUCCESS; > > +} > > + > > +static void pivot_hpt(CPUState *cs, run_on_cpu_data arg) > > +{ > > + sPAPRMachineState *spapr = SPAPR_MACHINE(arg.host_ptr); > > + PowerPCCPU *cpu = POWERPC_CPU(cs); > > + > > + cpu_synchronize_state(cs); > > + ppc_hash64_set_external_hpt(cpu, spapr->htab, spapr->htab_shift, > > + &error_fatal); > > } > > > > static target_ulong h_resize_hpt_commit(PowerPCCPU *cpu, > > @@ -378,13 +679,52 @@ static target_ulong h_resize_hpt_commit(PowerPCCPU > > *cpu, > > { > > target_ulong flags = args[0]; > > target_ulong shift = args[1]; > > + sPAPRPendingHPT *pending = spapr->pending_hpt; > > + int rc; > > + size_t newsize; > > Why size_t here? size_t could be 32-bit on some systems, and don't you > rather want to always have 64-bit (or at least target_ulong) here? In that case (and if newsize would be > 4G) we're stuffed anyway - we allocate the htab with qemu_memalign(), which only takes a size_t, and even if it didn't there's nowhere we could actually allocate the hash table. > > if (spapr->resize_hpt == SPAPR_RESIZE_HPT_DISABLED) { > > return H_AUTHORITY; > > } > > > > trace_spapr_h_resize_hpt_commit(flags, shift); > > - return H_HARDWARE; > > + > > + if (flags != 0) { > > + return H_PARAMETER; > > + } > > + > > + if (!pending || (pending->shift != shift)) { > > + /* no matching prepare */ > > + return H_CLOSED; > > + } > > + > > + if (!pending->complete) { > > + /* prepare has not completed */ > > + return H_BUSY; > > + } > > + > > + newsize = 1ULL << pending->shift; > > + rc = rehash_hpt(cpu, spapr->htab, HTAB_SIZE(spapr), > > + pending->hpt, newsize); > > + if (rc == H_SUCCESS) { > > + CPUState *cs; > > + > > + qemu_vfree(spapr->htab); > > + spapr->htab = pending->hpt; > > + spapr->htab_shift = pending->shift; > > + > > + CPU_FOREACH(cs) { > > + run_on_cpu(cs, pivot_hpt, RUN_ON_CPU_HOST_PTR(spapr)); > > + } > > + > > + pending->hpt = NULL; /* so it's not free()d */ > > + } > > + > > + /* Clean up */ > > + spapr->pending_hpt = NULL; > > + free_pending_hpt(pending); > > + > > + return rc; > > } > > Thomas > > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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