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Re: [qemu-s390x] [PATCH for-4.2 v3 1/2] kvm: s390: split too big memory
From: |
Christian Borntraeger |
Subject: |
Re: [qemu-s390x] [PATCH for-4.2 v3 1/2] kvm: s390: split too big memory section on several memslots |
Date: |
Fri, 2 Aug 2019 15:50:47 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 |
On 02.08.19 15:32, 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 baord 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 <address@hidden>
> ---
> 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.
> ---
/home/cborntra/REPOS/qemu/target/s390x/kvm.c: In function ‘kvm_arch_init’:
/home/cborntra/REPOS/qemu/target/s390x/kvm.c:350:5: error: implicit declaration
of function ‘kvm_set_max_memslot_size’; did you mean ‘kvm_get_max_memslots’?
[-Werror=implicit-function-declaration]
350 | kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES);
| ^~~~~~~~~~~~~~~~~~~~~~~~
| kvm_get_max_memslots
/home/cborntra/REPOS/qemu/target/s390x/kvm.c:350:5: error: nested extern
declaration of ‘kvm_set_max_memslot_size’ [-Werror=nested-externs]
cc1: all warnings being treated as errors
make[1]: *** [/home/cborntra/REPOS/qemu/rules.mak:69: target/s390x/kvm.o] Error
1
make: *** [Makefile:472: s390x-softmmu/all] Error 2
We probably need an include of sysemu/kvm_int.h in target/s390x/kvm.c
I will test with that fixup....
> include/hw/s390x/s390-virtio-ccw.h | 10 ++++
> include/sysemu/kvm_int.h | 1 +
> accel/kvm/kvm-all.c | 79 ++++++++++++++++++------------
> hw/s390x/s390-virtio-ccw.c | 9 ----
> target/s390x/kvm.c | 1 +
> 5 files changed, 60 insertions(+), 40 deletions(-)
>
> diff --git a/include/hw/s390x/s390-virtio-ccw.h
> b/include/hw/s390x/s390-virtio-ccw.h
> index 8aa27199c9..00632f94b4 100644
> --- a/include/hw/s390x/s390-virtio-ccw.h
> +++ b/include/hw/s390x/s390-virtio-ccw.h
> @@ -21,6 +21,16 @@
> #define S390_MACHINE_CLASS(klass) \
> OBJECT_CLASS_CHECK(S390CcwMachineClass, (klass), TYPE_S390_CCW_MACHINE)
>
> +/*
> + * 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)
> +
> typedef struct S390CcwMachineState {
> /*< private >*/
> MachineState parent_obj;
> diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
> index 31df465fdc..7f7520bce2 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 f450f25295..7a6efb9612 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -138,6 +138,7 @@ 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),
> @@ -951,6 +952,14 @@ 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)
> {
> @@ -958,7 +967,7 @@ 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)) {
> @@ -983,41 +992,49 @@ 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;
> + 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;
> + } while ((size -= slot_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;
> + 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;
> + } while ((size -= slot_size));
>
> out:
> kvm_slots_unlock(kml);
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 5b6a9a4e55..0c03ffb7c7 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -151,15 +151,6 @@ 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)
> 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 6e814c230b..d0267da8e1 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -347,6 +347,7 @@ 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;
> }
>
>