On 2/24/2022 12:56 PM, Dr. David Alan Gilbert wrote:
> * Steve Sistare (steven.sist...@oracle.com) wrote:
>> Allocate anonymous memory using memfd_create if the memfd-alloc machine
>> option is set.
>>
>> Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
>
> So other than the minor error nit that Guoyi spotted, I think this is
> pretty good, one other comment below:
>
>> ---
>> hw/core/machine.c | 19 +++++++++++++++++++
>> include/hw/boards.h | 1 +
>> qemu-options.hx | 6 ++++++
>> softmmu/physmem.c | 47 ++++++++++++++++++++++++++++++++++++++---------
>> softmmu/vl.c | 1 +
>> trace-events | 1 +
>> util/qemu-config.c | 4 ++++
>> 7 files changed, 70 insertions(+), 9 deletions(-)
>>
>> diff --git a/hw/core/machine.c b/hw/core/machine.c
>> index 53a99ab..7739d88 100644
>> --- a/hw/core/machine.c
>> +++ b/hw/core/machine.c
>> @@ -392,6 +392,20 @@ static void machine_set_mem_merge(Object *obj, bool
>> value, Error **errp)
>> ms->mem_merge = value;
>> }
>>
>> +static bool machine_get_memfd_alloc(Object *obj, Error **errp)
>> +{
>> + MachineState *ms = MACHINE(obj);
>> +
>> + return ms->memfd_alloc;
>> +}
>> +
>> +static void machine_set_memfd_alloc(Object *obj, bool value, Error **errp)
>> +{
>> + MachineState *ms = MACHINE(obj);
>> +
>> + ms->memfd_alloc = value;
>> +}
>> +
>> static bool machine_get_usb(Object *obj, Error **errp)
>> {
>> MachineState *ms = MACHINE(obj);
>> @@ -829,6 +843,11 @@ static void machine_class_init(ObjectClass *oc, void
>> *data)
>> object_class_property_set_description(oc, "mem-merge",
>> "Enable/disable memory merge support");
>>
>> + object_class_property_add_bool(oc, "memfd-alloc",
>> + machine_get_memfd_alloc, machine_set_memfd_alloc);
>> + object_class_property_set_description(oc, "memfd-alloc",
>> + "Enable/disable allocating anonymous memory using memfd_create");
>> +
>> object_class_property_add_bool(oc, "usb",
>> machine_get_usb, machine_set_usb);
>> object_class_property_set_description(oc, "usb",
>> diff --git a/include/hw/boards.h b/include/hw/boards.h
>> index 9c1c190..a57d7a0 100644
>> --- a/include/hw/boards.h
>> +++ b/include/hw/boards.h
>> @@ -327,6 +327,7 @@ struct MachineState {
>> char *dt_compatible;
>> bool dump_guest_core;
>> bool mem_merge;
>> + bool memfd_alloc;
>> bool usb;
>> bool usb_disabled;
>> char *firmware;
>> diff --git a/qemu-options.hx b/qemu-options.hx
>> index 7d47510..33c8173 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -30,6 +30,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>> " vmport=on|off|auto controls emulation of vmport
>> (default: auto)\n"
>> " dump-guest-core=on|off include guest memory in a core
>> dump (default=on)\n"
>> " mem-merge=on|off controls memory merge support
>> (default: on)\n"
>> + " memfd-alloc=on|off controls allocating anonymous guest
>> RAM using memfd_create (default: off)\n"
>> " aes-key-wrap=on|off controls support for AES key
>> wrapping (default=on)\n"
>> " dea-key-wrap=on|off controls support for DEA key
>> wrapping (default=on)\n"
>> " suppress-vmdesc=on|off disables self-describing
>> migration (default=off)\n"
>> @@ -76,6 +77,11 @@ SRST
>> supported by the host, de-duplicates identical memory pages
>> among VMs instances (enabled by default).
>>
>> + ``memfd-alloc=on|off``
>> + Enables or disables allocation of anonymous guest RAM using
>> + memfd_create. Any associated memory-backend objects are created
>> with
>> + share=on. The memfd-alloc default is off.
>> +
>> ``aes-key-wrap=on|off``
>> Enables or disables AES key wrapping support on s390-ccw hosts.
>> This feature controls whether AES wrapping keys will be created
>> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
>> index 3524c04..95e2b49 100644
>> --- a/softmmu/physmem.c
>> +++ b/softmmu/physmem.c
>> @@ -41,6 +41,7 @@
>> #include "qemu/config-file.h"
>> #include "qemu/error-report.h"
>> #include "qemu/qemu-print.h"
>> +#include "qemu/memfd.h"
>> #include "exec/memory.h"
>> #include "exec/ioport.h"
>> #include "sysemu/dma.h"
>> @@ -1964,35 +1965,63 @@ static void ram_block_add(RAMBlock *new_block, Error
>> **errp)
>> const bool shared = qemu_ram_is_shared(new_block);
>> RAMBlock *block;
>> RAMBlock *last_block = NULL;
>> + struct MemoryRegion *mr = new_block->mr;
>> ram_addr_t old_ram_size, new_ram_size;
>> Error *err = NULL;
>> + const char *name;
>> + void *addr = 0;
>> + size_t maxlen;
>
> You could move some of these down to the top of the block you're using
> them.
Will do.
One question: I added this to shorten lines and make my code additions more
readable:
size_t maxlen;
maxlen = new_block->max_length;
However, I did not change new_block->max_length to maxlen in the second half of
the
function which I did not modify, to avoid noise in the patch that is unrelated
to cpr.
Making those changes would shorten a few multi-liners. What is your preference
--
make those changes or not?
- Steve
>> + MachineState *ms = MACHINE(qdev_get_machine());
>>
>> old_ram_size = last_ram_page();
>>
>> qemu_mutex_lock_ramlist();
>> - new_block->offset = find_ram_offset(new_block->max_length);
>> + maxlen = new_block->max_length;
>> + new_block->offset = find_ram_offset(maxlen);
>>
>> if (!new_block->host) {
>> if (xen_enabled()) {
>> - xen_ram_alloc(new_block->offset, new_block->max_length,
>> - new_block->mr, &err);
>> + xen_ram_alloc(new_block->offset, maxlen, new_block->mr, &err);
>> if (err) {
>> error_propagate(errp, err);
>> qemu_mutex_unlock_ramlist();
>> return;
>> }
>> } else {
>> - new_block->host = qemu_anon_ram_alloc(new_block->max_length,
>> - &new_block->mr->align,
>> - shared, noreserve);
>> - if (!new_block->host) {
>> + name = memory_region_name(mr);
>> + if (ms->memfd_alloc) {
>> + Object *parent = &mr->parent_obj;
>> + int mfd = -1; /* placeholder until next patch */
>> + mr->align = QEMU_VMALLOC_ALIGN;
>> + if (mfd < 0) {
>> + mfd = qemu_memfd_create(name, maxlen + mr->align,
>> + 0, 0, 0, &err);
>> + if (mfd < 0) {
>> + return;
>> + }
>> + }
>> + qemu_set_cloexec(mfd);
>> + /* The memory backend already set its desired flags. */
>> + if (!object_dynamic_cast(parent, TYPE_MEMORY_BACKEND)) {
>> + new_block->flags |= RAM_SHARED;
>> + }
>> + addr = file_ram_alloc(new_block, maxlen, mfd,
>> + false, false, 0, errp);
>> + trace_anon_memfd_alloc(name, maxlen, addr, mfd);
>> + } else {
>> + addr = qemu_anon_ram_alloc(maxlen, &mr->align,
>> + shared, noreserve);
>> + }
>> +
>> + if (!addr) {
>> error_setg_errno(errp, errno,
>> "cannot set up guest memory '%s'",
>> - memory_region_name(new_block->mr));
>> + name);
>> qemu_mutex_unlock_ramlist();
>> return;
>> }
>> - memory_try_enable_merging(new_block->host,
>> new_block->max_length);
>> + memory_try_enable_merging(addr, maxlen);
>> + new_block->host = addr;
>> }
>> }
>>
>> diff --git a/softmmu/vl.c b/softmmu/vl.c
>> index 620a1f1..ab3648a 100644
>> --- a/softmmu/vl.c
>> +++ b/softmmu/vl.c
>> @@ -2440,6 +2440,7 @@ static void create_default_memdev(MachineState *ms,
>> const char *path)
>> object_property_set_str(obj, "mem-path", path, &error_fatal);
>> }
>> object_property_set_int(obj, "size", ms->ram_size, &error_fatal);
>> + object_property_set_bool(obj, "share", ms->memfd_alloc, &error_fatal);
>> object_property_add_child(object_get_objects_root(), mc->default_ram_id,
>> obj);
>> /* Ensure backend's memory region name is equal to mc->default_ram_id */
>> diff --git a/trace-events b/trace-events
>> index a637a61..770a9ac 100644
>> --- a/trace-events
>> +++ b/trace-events
>> @@ -45,6 +45,7 @@ ram_block_discard_range(const char *rbname, void *hva,
>> size_t length, bool need_
>> # accel/tcg/cputlb.c
>> memory_notdirty_write_access(uint64_t vaddr, uint64_t ram_addr, unsigned
>> size) "0x%" PRIx64 " ram_addr 0x%" PRIx64 " size %u"
>> memory_notdirty_set_dirty(uint64_t vaddr) "0x%" PRIx64
>> +anon_memfd_alloc(const char *name, size_t size, void *ptr, int fd) "%s size
>> %zu ptr %p fd %d"
>>
>> # gdbstub.c
>> gdbstub_op_start(const char *device) "Starting gdbstub using device %s"
>> diff --git a/util/qemu-config.c b/util/qemu-config.c
>> index 436ab63..3606e5c 100644
>> --- a/util/qemu-config.c
>> +++ b/util/qemu-config.c
>> @@ -207,6 +207,10 @@ static QemuOptsList machine_opts = {
>> .type = QEMU_OPT_BOOL,
>> .help = "enable/disable memory merge support",
>> },{
>> + .name = "memfd-alloc",
>> + .type = QEMU_OPT_BOOL,
>> + .help = "enable/disable memfd_create for anonymous memory",
>> + },{
>> .name = "usb",
>> .type = QEMU_OPT_BOOL,
>> .help = "Set on/off to enable/disable usb",
>> --
>> 1.8.3.1
>>
