On Mon, May 04, 2026 at 04:30:18PM +0400, Marc-André Lureau wrote:
> Add a new 'info ramblock-attributes' HMP command and the corresponding
> 'x-query-ramblock-attributes' QMP command to display the shared/private
> memory attributes for ram blocks.
>
> The QMP command returns structured data (RamBlockAttributesInfo list
> with per-range shared/populated attributes), while HMP formats it for
> human consumption.
>
> This is useful for debugging confidential guests (TDX, SNP) to inspect
> which memory regions are shared vs private, and their population state
> when a RamDiscardManager is present (e.g. virtio-mem).
>
> Signed-off-by: Marc-André Lureau <[email protected]>
Nobody is copied on this patch.. Let me add Markus and Dave at minimum..
Only one trivial question below:
> ---
> qapi/machine.json | 55 +++++++++++++++++++++++++++++++++
> include/monitor/hmp.h | 1 +
> hw/core/machine-hmp-cmds.c | 32 +++++++++++++++++++
> system/ram-block-attributes.c | 72
> +++++++++++++++++++++++++++++++++++++++++++
> hmp-commands-info.hx | 13 ++++++++
> 5 files changed, 173 insertions(+)
>
> diff --git a/qapi/machine.json b/qapi/machine.json
> index 685e4e29b87..aac8a235cf6 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1738,6 +1738,61 @@
> 'returns': 'HumanReadableText',
> 'features': [ 'unstable' ] }
>
> +##
> +# @RamBlockAttributeRange:
> +#
> +# A contiguous range within a ram block with uniform attributes.
> +#
> +# @start: start offset in bytes within the ram block
> +#
> +# @length: length in bytes of the range
> +#
> +# @shared: true if the range is shared, false if private
> +#
> +# @populated: true if the range is populated (only present when a
> +# RamDiscardManager is managing the block)
> +#
> +# Since: 11.1
> +##
> +{ 'struct': 'RamBlockAttributeRange',
> + 'data': { 'start': 'uint64',
> + 'length': 'uint64',
> + 'shared': 'bool',
> + '*populated': 'bool' } }
> +
> +##
> +# @RamBlockAttributesInfo:
> +#
> +# Shared/private memory attributes for a ram block.
> +#
> +# @name: the ram block identifier
> +#
> +# @ranges: list of attribute ranges
> +#
> +# Since: 11.1
> +##
> +{ 'struct': 'RamBlockAttributesInfo',
> + 'data': { 'name': 'str',
> + 'ranges': [ 'RamBlockAttributeRange' ] } }
> +
> +##
> +# @x-query-ramblock-attributes:
> +#
> +# Query ram block shared/private attributes. This is useful
> +# to debug confidential guests.
> +#
> +# Features:
> +#
> +# @unstable: This command is meant for debugging.
> +#
> +# Returns: list of ram block attributes
> +#
> +# Since: 11.1
> +##
> +{ 'command': 'x-query-ramblock-attributes',
> + 'returns': [ 'RamBlockAttributesInfo' ],
> + 'features': [ 'unstable' ] }
> +
> ##
> # @x-query-roms:
> #
> diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h
> index e222bea60cd..4493952b417 100644
> --- a/include/monitor/hmp.h
> +++ b/include/monitor/hmp.h
> @@ -143,6 +143,7 @@ void hmp_info_dump(Monitor *mon, const QDict *qdict);
> void hmp_hotpluggable_cpus(Monitor *mon, const QDict *qdict);
> void hmp_info_vm_generation_id(Monitor *mon, const QDict *qdict);
> void hmp_info_memory_size_summary(Monitor *mon, const QDict *qdict);
> +void hmp_info_ramblock_attributes(Monitor *mon, const QDict *qdict);
> void hmp_info_replay(Monitor *mon, const QDict *qdict);
> void hmp_replay_break(Monitor *mon, const QDict *qdict);
> void hmp_replay_delete_break(Monitor *mon, const QDict *qdict);
> diff --git a/hw/core/machine-hmp-cmds.c b/hw/core/machine-hmp-cmds.c
> index 46846f741a2..122e1a0f735 100644
> --- a/hw/core/machine-hmp-cmds.c
> +++ b/hw/core/machine-hmp-cmds.c
> @@ -24,6 +24,7 @@
> #include "qapi/string-output-visitor.h"
> #include "qemu/error-report.h"
> #include "system/numa.h"
> +#include "system/ramblock.h"
> #include "hw/core/boards.h"
>
> void hmp_info_cpus(Monitor *mon, const QDict *qdict)
> @@ -388,3 +389,34 @@ void hmp_info_memory_size_summary(Monitor *mon, const
> QDict *qdict)
> }
> hmp_handle_error(mon, err);
> }
> +
> +void hmp_info_ramblock_attributes(Monitor *mon, const QDict *qdict)
> +{
> + Error *err = NULL;
> + g_autoptr(RamBlockAttributesInfoList) list = NULL;
> + RamBlockAttributesInfoList *it;
> +
> + list = qmp_x_query_ramblock_attributes(&err);
> + if (hmp_handle_error(mon, err)) {
> + return;
> + }
> +
> + for (it = list; it; it = it->next) {
> + RamBlockAttributesInfo *rba = it->value;
> + RamBlockAttributeRangeList *r;
> +
> + monitor_printf(mon, "%s:\n", rba->name);
> + for (r = rba->ranges; r; r = r->next) {
> + RamBlockAttributeRange *range = r->value;
> + const char *shared = range->shared ? "shared" : "private";
> + const char *pop = range->has_populated ?
> + (range->populated ? "+populated" : "-populated") : "";
> +
> + monitor_printf(mon,
> + " 0x%016" PRIx64 "-0x%016" PRIx64 " %s%s\n",
> + range->start,
> + range->start + range->length - 1,
> + shared, pop);
> + }
> + }
> +}
> diff --git a/system/ram-block-attributes.c b/system/ram-block-attributes.c
> index 59ec7a28eb0..f9573801b60 100644
> --- a/system/ram-block-attributes.c
> +++ b/system/ram-block-attributes.c
> @@ -11,6 +11,7 @@
>
> #include "qemu/osdep.h"
> #include "qemu/error-report.h"
> +#include "qapi/qapi-commands-machine.h"
> #include "system/ramblock.h"
> #include "trace.h"
>
> @@ -221,3 +222,74 @@ static void ram_block_attributes_class_init(ObjectClass
> *klass,
> rdsc->get_min_granularity = ram_block_attributes_rds_get_min_granularity;
> rdsc->is_populated = ram_block_attributes_rds_is_populated;
> }
> +
> +RamBlockAttributesInfoList *qmp_x_query_ramblock_attributes(Error **errp)
> +{
> + RamBlockAttributesInfoList *head = NULL, **tail = &head;
> + RAMBlock *block;
> + size_t rba_block_size = ram_block_attributes_get_block_size();
> +
> + RCU_READ_LOCK_GUARD();
> +
> + RAMBLOCK_FOREACH(block) {
> + RamBlockAttributesInfo *rba;
> + RamBlockAttributeRangeList **range_tail;
> + RamBlockAttributes *attr = block->attributes;
> + RamDiscardManager *rdm;
> + bool has_rdm;
> + unsigned long pos;
> +
> + if (!attr) {
> + continue;
> + }
> +
> + rdm = memory_region_get_ram_discard_manager(block->mr);
> + has_rdm = rdm != NULL;
> +
> + rba = g_new0(RamBlockAttributesInfo, 1);
> + rba->name = g_strdup(block->idstr);
> + range_tail = &rba->ranges;
> +
> + pos = 0;
> + while (pos < attr->bitmap_size) {
> + bool is_shared = test_bit(pos, attr->bitmap);
> + unsigned long next;
> + uint64_t start_offset, length;
> + RamBlockAttributeRange *range;
> +
> + if (is_shared) {
> + next = find_next_zero_bit(attr->bitmap,
> + attr->bitmap_size, pos);
> + } else {
> + next = find_next_bit(attr->bitmap,
> + attr->bitmap_size, pos);
> + }
> +
> + start_offset = (uint64_t)pos * rba_block_size;
> + length = (uint64_t)(next - pos) * rba_block_size;
> +
> + range = g_new0(RamBlockAttributeRange, 1);
> + range->start = start_offset;
> + range->length = length;
> + range->shared = is_shared;
> +
> + if (has_rdm) {
Is this only for extra safety? My understanding is when reaching here,
attr!=NULL, which means we have at least one disgard manager source, then
the manager must be there. So I wonder if we could assert. But not a big
deal. Maybe I overlooked that it is needed?
> + MemoryRegionSection section = {
> + .mr = block->mr,
> + .offset_within_region = start_offset,
> + .size = int128_make64(length),
> + };
> + range->has_populated = true;
> + range->populated =
> + ram_discard_manager_is_populated(rdm, §ion);
> + }
> +
> + QAPI_LIST_APPEND(range_tail, range);
> + pos = next;
> + }
> +
> + QAPI_LIST_APPEND(tail, rba);
> + }
> +
> + return head;
> +}
> diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
> index 74c741f80e2..1168b4c20ca 100644
> --- a/hmp-commands-info.hx
> +++ b/hmp-commands-info.hx
> @@ -774,6 +774,19 @@ SRST
> Dump all the ramblocks of the system.
> ERST
>
> + {
> + .name = "ramblock-attributes",
> + .args_type = "",
> + .params = "",
> + .help = "Display ramblock shared/private attributes",
> + .cmd = hmp_info_ramblock_attributes,
> + },
> +
> +SRST
> + ``info ramblock-attributes``
> + Display the shared/private memory attributes for ram blocks.
> +ERST
> +
> {
> .name = "hotpluggable-cpus",
> .args_type = "",
>
> --
> 2.54.0
>
>
--
Peter Xu
