On Mon, Sep 16, 2019 at 09:23:46AM -0400, Igor Mammedov wrote:
> Max memslot size supported by kvm on s390 is 8Tb,
> move logic of splitting RAM in chunks upto 8T to KVM code.
>
> This way it will hide KVM specific restrictions in KVM code
> and won't affect board level design decisions. Which would allow
> us to avoid misusing memory_region_allocate_system_memory() API
> and eventually use a single hostmem backend for guest RAM.
>
> Signed-off-by: Igor Mammedov <imamm...@redhat.com>
> ---
> Since there is quite a bit of migration related code churn in the patch
> CCing migration maintainer
>
> CC: dgilb...@redhat.com
>
> v6:
> * KVM's migration code was assuming 1:1 relation between
> memslot and MemorySection, which becomes not true fo s390x
> with this patch. As result migration was broken and
> dirty logging wasn't even started with when a MemorySection
> was split on several memslots. Amend related KVM dirty
> log tracking code to account for split MemorySection.
> v5:
> * move computation 'size -= slot_size' inside of loop body
> (David Hildenbrand <da...@redhat.com>)
> v4:
> * fix compilation issue
> (Christian Borntraeger <borntrae...@de.ibm.com>)
> * advance HVA along with GPA in kvm_set_phys_mem()
> (Christian Borntraeger <borntrae...@de.ibm.com>)
>
> patch prepares only KVM side for switching to single RAM memory region
> another patch will take care of dropping manual RAM partitioning in
> s390 code.
>
>
> include/sysemu/kvm_int.h | 1 +
> accel/kvm/kvm-all.c | 239 ++++++++++++++++++++++---------------
> hw/s390x/s390-virtio-ccw.c | 9 --
> target/s390x/kvm.c | 12 ++
> 4 files changed, 159 insertions(+), 102 deletions(-)
>
> diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
> index 72b2d1b3ae..ac2d1f8b56 100644
> --- a/include/sysemu/kvm_int.h
> +++ b/include/sysemu/kvm_int.h
> @@ -41,4 +41,5 @@ typedef struct KVMMemoryListener {
> void kvm_memory_listener_register(KVMState *s, KVMMemoryListener *kml,
> AddressSpace *as, int as_id);
>
> +void kvm_set_max_memslot_size(hwaddr max_slot_size);
> #endif
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index b09bad0804..0635903408 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -140,6 +140,7 @@ bool kvm_direct_msi_allowed;
> bool kvm_ioeventfd_any_length_allowed;
> bool kvm_msi_use_devid;
> static bool kvm_immediate_exit;
> +static hwaddr kvm_max_slot_size = ~0;
>
> static const KVMCapabilityInfo kvm_required_capabilites[] = {
> KVM_CAP_INFO(USER_MEMORY),
> @@ -437,7 +438,7 @@ static int kvm_slot_update_flags(KVMMemoryListener *kml,
> KVMSlot *mem,
> static int kvm_section_update_flags(KVMMemoryListener *kml,
> MemoryRegionSection *section)
> {
> - hwaddr start_addr, size;
> + hwaddr start_addr, size, slot_size;
> KVMSlot *mem;
> int ret = 0;
>
> @@ -448,13 +449,18 @@ static int kvm_section_update_flags(KVMMemoryListener
> *kml,
>
> kvm_slots_lock(kml);
>
> - mem = kvm_lookup_matching_slot(kml, start_addr, size);
> - if (!mem) {
> - /* We don't have a slot if we want to trap every access. */
> - goto out;
> - }
> + while (size && !ret) {
> + slot_size = kvm_max_slot_size < size ? kvm_max_slot_size : size;
Nit: use MIN()?
> + mem = kvm_lookup_matching_slot(kml, start_addr, slot_size);
> + if (!mem) {
> + /* We don't have a slot if we want to trap every access. */
> + goto out;
I don't really understand the rational behind e377e87ca6a3d by simply
reading the commit message... Just want to make sure: this won't be
triggered when memslot split happened for this memory region section,
right?
> + }
>
> - ret = kvm_slot_update_flags(kml, mem, section->mr);
> + ret = kvm_slot_update_flags(kml, mem, section->mr);
> + start_addr += slot_size;
> + size -= slot_size;
> + }
>
> out:
> kvm_slots_unlock(kml);
> @@ -497,11 +503,14 @@ static void kvm_log_stop(MemoryListener *listener,
>
> /* get kvm's dirty pages bitmap and update qemu's */
> static int kvm_get_dirty_pages_log_range(MemoryRegionSection *section,
> + hwaddr offset_in_section,
> + hwaddr range_size,
> unsigned long *bitmap)
> {
> ram_addr_t start = section->offset_within_region +
> + offset_in_section +
> memory_region_get_ram_addr(section->mr);
> - ram_addr_t pages = int128_get64(section->size) / getpagesize();
> + ram_addr_t pages = range_size / getpagesize();
I feel like we can avoid touching kvm_get_dirty_pages_log_range() by
passing in a correct MemoryRegionSection* to it (please see [1]
below).
>
> cpu_physical_memory_set_dirty_lebitmap(bitmap, start, pages);
> return 0;
> @@ -527,11 +536,13 @@ static int
> kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
> struct kvm_dirty_log d = {};
> KVMSlot *mem;
> hwaddr start_addr, size;
> + hwaddr slot_size, slot_offset = 0;
> int ret = 0;
>
> size = kvm_align_section(section, &start_addr);
> - if (size) {
> - mem = kvm_lookup_matching_slot(kml, start_addr, size);
> + while (size) {
> + slot_size = kvm_max_slot_size < size ? kvm_max_slot_size : size;
(use MIN?)
> + mem = kvm_lookup_matching_slot(kml, start_addr, slot_size);
> if (!mem) {
> /* We don't have a slot if we want to trap every access. */
> goto out;
> @@ -549,11 +560,11 @@ static int
> kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
> * So for now, let's align to 64 instead of HOST_LONG_BITS here, in
> * a hope that sizeof(long) won't become >8 any time soon.
> */
> - size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS),
> - /*HOST_LONG_BITS*/ 64) / 8;
> if (!mem->dirty_bmap) {
> + hwaddr bitmap_size = ALIGN(((mem->memory_size) >>
> TARGET_PAGE_BITS),
> + /*HOST_LONG_BITS*/ 64) / 8;
> /* Allocate on the first log_sync, once and for all */
> - mem->dirty_bmap = g_malloc0(size);
> + mem->dirty_bmap = g_malloc0(bitmap_size);
> }
>
> d.dirty_bitmap = mem->dirty_bmap;
> @@ -564,7 +575,12 @@ static int
> kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
> goto out;
> }
>
> - kvm_get_dirty_pages_log_range(section, d.dirty_bitmap);
> + kvm_get_dirty_pages_log_range(section, slot_offset, slot_size,
> + d.dirty_bitmap);
[1]
Here can we hand-made a MemoryRegionSection which covers the
slot_offset/slot_size region and pass it to
kvm_get_dirty_pages_log_range()?
> +
> + slot_offset += slot_size;
> + start_addr += slot_size;
> + size -= slot_size;
> }
> out:
> return ret;
> @@ -575,55 +591,14 @@ out:
> #define KVM_CLEAR_LOG_ALIGN (qemu_real_host_page_size <<
> KVM_CLEAR_LOG_SHIFT)
> #define KVM_CLEAR_LOG_MASK (-KVM_CLEAR_LOG_ALIGN)
>
> -/**
> - * kvm_physical_log_clear - Clear the kernel's dirty bitmap for range
> - *
> - * NOTE: this will be a no-op if we haven't enabled manual dirty log
> - * protection in the host kernel because in that case this operation
> - * will be done within log_sync().
> - *
> - * @kml: the kvm memory listener
> - * @section: the memory range to clear dirty bitmap
> - */
> -static int kvm_physical_log_clear(KVMMemoryListener *kml,
> - MemoryRegionSection *section)
> +static int kvm_physical_log_slot_clear(uint64_t start, uint64_t size,
> + KVMSlot *mem, int as_id)
> {
> KVMState *s = kvm_state;
> - struct kvm_clear_dirty_log d;
> - uint64_t start, end, bmap_start, start_delta, bmap_npages, size;
> unsigned long *bmap_clear = NULL, psize = qemu_real_host_page_size;
> - KVMSlot *mem = NULL;
> - int ret, i;
> -
> - if (!s->manual_dirty_log_protect) {
> - /* No need to do explicit clear */
> - return 0;
> - }
> -
> - start = section->offset_within_address_space;
> - size = int128_get64(section->size);
> -
> - if (!size) {
> - /* Nothing more we can do... */
> - return 0;
> - }
> -
> - kvm_slots_lock(kml);
> -
> - /* Find any possible slot that covers the section */
> - for (i = 0; i < s->nr_slots; i++) {
> - mem = &kml->slots[i];
> - if (mem->start_addr <= start &&
> - start + size <= mem->start_addr + mem->memory_size) {
> - break;
> - }
> - }
> -
> - /*
> - * We should always find one memslot until this point, otherwise
> - * there could be something wrong from the upper layer
> - */
> - assert(mem && i != s->nr_slots);
> + uint64_t end, bmap_start, start_delta, bmap_npages;
> + struct kvm_clear_dirty_log d;
> + int ret;
>
> /*
> * We need to extend either the start or the size or both to
> @@ -694,7 +669,7 @@ static int kvm_physical_log_clear(KVMMemoryListener *kml,
> /* It should never overflow. If it happens, say something */
> assert(bmap_npages <= UINT32_MAX);
> d.num_pages = bmap_npages;
> - d.slot = mem->slot | (kml->as_id << 16);
> + d.slot = mem->slot | (as_id << 16);
>
> if (kvm_vm_ioctl(s, KVM_CLEAR_DIRTY_LOG, &d) == -1) {
> ret = -errno;
> @@ -718,8 +693,66 @@ static int kvm_physical_log_clear(KVMMemoryListener *kml,
> /* This handles the NULL case well */
> g_free(bmap_clear);
>
> - kvm_slots_unlock(kml);
> + return ret;
> +}
> +
> +/**
> + * kvm_physical_log_clear - Clear the kernel's dirty bitmap for range
> + *
> + * NOTE: this will be a no-op if we haven't enabled manual dirty log
> + * protection in the host kernel because in that case this operation
> + * will be done within log_sync().
> + *
> + * @kml: the kvm memory listener
> + * @section: the memory range to clear dirty bitmap
> + */
> +static int kvm_physical_log_clear(KVMMemoryListener *kml,
> + MemoryRegionSection *section)
> +{
> + KVMState *s = kvm_state;
> + uint64_t start, size, slot_size;
> + KVMSlot *mem = NULL;
> + int i, ret = 0;
> +
> + if (!s->manual_dirty_log_protect) {
> + /* No need to do explicit clear */
> + return 0;
> + }
> +
> + start = section->offset_within_address_space;
> + size = int128_get64(section->size);
> +
> + if (!size) {
> + /* Nothing more we can do... */
> + return 0;
> + }
> +
> + kvm_slots_lock(kml);
> +
> + while (size) {
> + slot_size = kvm_max_slot_size < size ? kvm_max_slot_size : size;
MIN?
Also, the naming of slot_size might be a bit misleading here because
log_clear() is different in that it could happen with very small
memory region section passed in, hence slot_size could very probably
not be the size of slot. Maybe range_size or anything else?
> + /* Iterate over slots that cover the section */
> + for (i = 0; i < s->nr_slots; i++) {
> + mem = &kml->slots[i];
> + if (mem->start_addr <= start &&
> + start + slot_size <= mem->start_addr + mem->memory_size) {
> + break;
> + }
> + }
>
> + /*
> + * We should always find one memslot until this point, otherwise
> + * there could be something wrong from the upper layer
> + */
> + assert(mem && i != s->nr_slots);
> +
> + kvm_physical_log_slot_clear(start, slot_size, mem, kml->as_id);
Use ret to capture errors?
> +
> + size -= slot_size;
> + start += slot_size;
> + }
> +
> + kvm_slots_unlock(kml);
> return ret;
> }
>
> @@ -953,6 +986,14 @@ kvm_check_extension_list(KVMState *s, const
> KVMCapabilityInfo *list)
> return NULL;
> }
>
> +void kvm_set_max_memslot_size(hwaddr max_slot_size)
> +{
> + g_assert(
> + ROUND_UP(max_slot_size, qemu_real_host_page_size) == max_slot_size
> + );
> + kvm_max_slot_size = max_slot_size;
> +}
> +
> static void kvm_set_phys_mem(KVMMemoryListener *kml,
> MemoryRegionSection *section, bool add)
> {
> @@ -960,7 +1001,7 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
> int err;
> MemoryRegion *mr = section->mr;
> bool writeable = !mr->readonly && !mr->rom_device;
> - hwaddr start_addr, size;
> + hwaddr start_addr, size, slot_size;
> void *ram;
>
> if (!memory_region_is_ram(mr)) {
> @@ -985,41 +1026,52 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
> kvm_slots_lock(kml);
>
> if (!add) {
> - mem = kvm_lookup_matching_slot(kml, start_addr, size);
> - if (!mem) {
> - goto out;
> - }
> - if (mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
> - kvm_physical_sync_dirty_bitmap(kml, section);
> - }
> + do {
> + slot_size = kvm_max_slot_size < size ? kvm_max_slot_size : size;
Same
> + mem = kvm_lookup_matching_slot(kml, start_addr, slot_size);
> + if (!mem) {
> + goto out;
> + }
> + if (mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
> + kvm_physical_sync_dirty_bitmap(kml, section);
> + }
>
> - /* unregister the slot */
> - g_free(mem->dirty_bmap);
> - mem->dirty_bmap = NULL;
> - mem->memory_size = 0;
> - mem->flags = 0;
> - err = kvm_set_user_memory_region(kml, mem, false);
> - if (err) {
> - fprintf(stderr, "%s: error unregistering slot: %s\n",
> - __func__, strerror(-err));
> - abort();
> - }
> + /* unregister the slot */
> + g_free(mem->dirty_bmap);
> + mem->dirty_bmap = NULL;
> + mem->memory_size = 0;
> + mem->flags = 0;
> + err = kvm_set_user_memory_region(kml, mem, false);
> + if (err) {
> + fprintf(stderr, "%s: error unregistering slot: %s\n",
> + __func__, strerror(-err));
> + abort();
> + }
> + start_addr += slot_size;
> + size -= slot_size;
> + } while (size);
> goto out;
> }
>
> /* register the new slot */
> - mem = kvm_alloc_slot(kml);
> - mem->memory_size = size;
> - mem->start_addr = start_addr;
> - mem->ram = ram;
> - mem->flags = kvm_mem_flags(mr);
> -
> - err = kvm_set_user_memory_region(kml, mem, true);
> - if (err) {
> - fprintf(stderr, "%s: error registering slot: %s\n", __func__,
> - strerror(-err));
> - abort();
> - }
> + do {
> + slot_size = kvm_max_slot_size < size ? kvm_max_slot_size : size;
Same.
> + mem = kvm_alloc_slot(kml);
> + mem->memory_size = slot_size;
> + mem->start_addr = start_addr;
> + mem->ram = ram;
> + mem->flags = kvm_mem_flags(mr);
> +
> + err = kvm_set_user_memory_region(kml, mem, true);
> + if (err) {
> + fprintf(stderr, "%s: error registering slot: %s\n", __func__,
> + strerror(-err));
> + abort();
> + }
> + start_addr += slot_size;
> + ram += slot_size;
> + size -= slot_size;
> + } while (size);
>
> out:
> kvm_slots_unlock(kml);
> @@ -2859,6 +2911,7 @@ static bool kvm_accel_has_memory(MachineState *ms,
> AddressSpace *as,
>
> for (i = 0; i < kvm->nr_as; ++i) {
> if (kvm->as[i].as == as && kvm->as[i].ml) {
> + size = kvm_max_slot_size < size ? kvm_max_slot_size : size;
> return NULL != kvm_lookup_matching_slot(kvm->as[i].ml,
> start_addr, size);
> }
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 8bfb6684cb..baa95aad38 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -154,15 +154,6 @@ static void virtio_ccw_register_hcalls(void)
> virtio_ccw_hcall_early_printk);
> }
>
> -/*
> - * KVM does only support memory slots up to KVM_MEM_MAX_NR_PAGES pages
> - * as the dirty bitmap must be managed by bitops that take an int as
> - * position indicator. If we have a guest beyond that we will split off
> - * new subregions. The split must happen on a segment boundary (1MB).
> - */
> -#define KVM_MEM_MAX_NR_PAGES ((1ULL << 31) - 1)
> -#define SEG_MSK (~0xfffffULL)
> -#define KVM_SLOT_MAX_BYTES ((KVM_MEM_MAX_NR_PAGES * TARGET_PAGE_SIZE) &
> SEG_MSK)
(Nit: IMHO it'll be cleaner to keep these and in the next patch to
simply revert bb223055b9b327e)
> static void s390_memory_init(ram_addr_t mem_size)
> {
> MemoryRegion *sysmem = get_system_memory();
> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index cea71ac7c3..838d23cb17 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -28,6 +28,7 @@
> #include "cpu.h"
> #include "internal.h"
> #include "kvm_s390x.h"
> +#include "sysemu/kvm_int.h"
> #include "qapi/error.h"
> #include "qemu/error-report.h"
> #include "qemu/timer.h"
> @@ -123,6 +124,16 @@
> #define VCPU_IRQ_BUF_SIZE(max_cpus) (sizeof(struct kvm_s390_irq) * \
> (max_cpus + NR_LOCAL_IRQS))
>
> +/*
> + * KVM does only support memory slots up to KVM_MEM_MAX_NR_PAGES pages
> + * as the dirty bitmap must be managed by bitops that take an int as
> + * position indicator. If we have a guest beyond that we will split off
> + * new subregions. The split must happen on a segment boundary (1MB).
> + */
> +#define KVM_MEM_MAX_NR_PAGES ((1ULL << 31) - 1)
Not related to this series, but... should kvm export this to uapi
headers?
> +#define SEG_MSK (~0xfffffULL)
> +#define KVM_SLOT_MAX_BYTES ((KVM_MEM_MAX_NR_PAGES * TARGET_PAGE_SIZE) &
> SEG_MSK)
> +
> static CPUWatchpoint hw_watchpoint;
> /*
> * We don't use a list because this structure is also used to transmit the
> @@ -348,6 +359,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
> */
> /* kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0); */
>
> + kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES);
> return 0;
> }
>
> --
> 2.18.1
>
>
Regards,
--
Peter Xu
