spapr: nested: Add support for reporting Hostwide state counter

Add support for reporting Hostwide state counters for nested KVM pseries
guests running with 'cap-nested-papr' on Qemu-TCG acting as
L0-hypervisor. The Hostwide state counters are statistics about state that
L0-hypervisor maintains for the L2-guests and represent the state of all
L2-guests, not just a specific one.

These stats counters are exposed to L1-Hypervisor by the L0-Hypervisor via a
new bit-flag named 'getHostWideState' for the H_GUEST_GET_STATE hcall which
is documented at [1]. Once this flag is set the hcall should populate the
Guest-State-Elements in the requested GSB with the stat counter
values. Currently following five counters are supported:

* l0_guest_heap_size_inuse
* l0_guest_heap_size_max
* l0_guest_pagetable_size_inuse
* l0_guest_pagetable_size_max
* l0_guest_pagetable_reclaimed

At the moment '0' is being reported for all these counters as these
counters doesn't align with how L0-Qemu manages Guest memory.

The patch implements support for these counters by adding new members to
the 'struct SpaprMachineStateNested'. These new members are then plugged
into the existing 'guest_state_element_types[]' with the help of a new
macro 'GSBE_NESTED_MACHINE_DW' together with a new helper
'get_machine_ptr()'. guest_state_request_check() is updated to ensure
correctness of the requested GSB and finally h_guest_getset_state() is
updated to handle the newly introduced flag
'GUEST_STATE_REQUEST_HOST_WIDE'.

This patch is tested with the proposed linux-kernel implementation to
expose these stat-counter as perf-events at [2].

[1]
https://lore.kernel.org/all/20241222140247.174998-2-vaibhav@linux.ibm.com

[2]
https://lore.kernel.org/all/20241222140247.174998-1-vaibhav@linux.ibm.com

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Message-ID: <20250221155449.530645-1-vaibhav@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

1 files changed, 61 insertions, 6 deletions

diff --git a/include/hw/ppc/spapr_nested.h b/include/hw/ppc/spapr_nested.h
index e420220484..f7be0d5a95 100644
--- a/include/hw/ppc/spapr_nested.h
+++ b/include/hw/ppc/spapr_nested.h
@@ -11,7 +11,13 @@
 #define GSB_TB_OFFSET           0x0004 /* Timebase Offset */
 #define GSB_PART_SCOPED_PAGETBL 0x0005 /* Partition Scoped Page Table */
 #define GSB_PROCESS_TBL         0x0006 /* Process Table */
-                    /* RESERVED 0x0007 - 0x0BFF */
+                    /* RESERVED 0x0007 - 0x07FF */
+#define GSB_L0_GUEST_HEAP_INUSE 0x0800 /* Guest Management Heap Size */
+#define GSB_L0_GUEST_HEAP_MAX   0x0801 /* Guest Management Heap Max Size */
+#define GSB_L0_GUEST_PGTABLE_SIZE_INUSE  0x0802 /* Guest Pagetable Size */
+#define GSB_L0_GUEST_PGTABLE_SIZE_MAX    0x0803 /* Guest Pagetable Max Size */
+#define GSB_L0_GUEST_PGTABLE_RECLAIMED   0x0804 /* Pagetable Reclaim in bytes */
+                    /* RESERVED 0x0805 - 0xBFF */
 #define GSB_VCPU_IN_BUFFER      0x0C00 /* Run VCPU Input Buffer */
 #define GSB_VCPU_OUT_BUFFER     0x0C01 /* Run VCPU Out Buffer */
 #define GSB_VCPU_VPA            0x0C02 /* HRA to Guest VCPU VPA */
@@ -196,6 +202,38 @@ typedef struct SpaprMachineStateNested {
 #define NESTED_API_PAPR    2
     bool capabilities_set;
     uint32_t pvr_base;
+
+    /**
+     * l0_guest_heap_inuse: The currently used bytes in the Hypervisor's Guest
+     * Management Space associated with the Host Partition.
+     **/
+    uint64_t l0_guest_heap_inuse;
+
+    /**
+     * host_heap_max: The maximum bytes available in the Hypervisor's Guest
+     * Management Space associated with the Host Partition.
+     **/
+    uint64_t l0_guest_heap_max;
+
+    /**
+     * host_pagetable: The currently used bytes in the Hypervisor's Guest
+     * Page Table Management Space associated with the Host Partition.
+     **/
+    uint64_t l0_guest_pgtable_size_inuse;
+
+    /**
+     * host_pagetable_max: The maximum bytes available in the Hypervisor's Guest
+     * Page Table Management Space associated with the Host Partition.
+     **/
+    uint64_t l0_guest_pgtable_size_max;
+
+    /**
+     * host_pagetable_reclaim: The amount of space in bytes that has been
+     * reclaimed due to overcommit in the  Hypervisor's Guest Page Table
+     * Management Space associated with the Host Partition.
+     **/
+    uint64_t l0_guest_pgtable_reclaimed;
+
     GHashTable *guests;
 } SpaprMachineStateNested;
 
@@ -229,9 +267,15 @@ typedef struct SpaprMachineStateNestedGuest {
 #define HVMASK_HDEXCR                 0x00000000FFFFFFFF
 #define HVMASK_TB_OFFSET              0x000000FFFFFFFFFF
 #define GSB_MAX_BUF_SIZE              (1024 * 1024)
-#define H_GUEST_GETSET_STATE_FLAG_GUEST_WIDE 0x8000000000000000
-#define GUEST_STATE_REQUEST_GUEST_WIDE       0x1
-#define GUEST_STATE_REQUEST_SET              0x2
+#define H_GUEST_GET_STATE_FLAGS_MASK   0xC000000000000000ULL
+#define H_GUEST_SET_STATE_FLAGS_MASK   0x8000000000000000ULL
+#define H_GUEST_SET_STATE_FLAGS_GUEST_WIDE 0x8000000000000000ULL
+#define H_GUEST_GET_STATE_FLAGS_GUEST_WIDE 0x8000000000000000ULL
+#define H_GUEST_GET_STATE_FLAGS_HOST_WIDE  0x4000000000000000ULL
+
+#define GUEST_STATE_REQUEST_GUEST_WIDE     0x1
+#define GUEST_STATE_REQUEST_HOST_WIDE      0x2
+#define GUEST_STATE_REQUEST_SET            0x4
 
 /*
  * As per ISA v3.1B, following bits are reserved:
@@ -251,6 +295,15 @@ typedef struct SpaprMachineStateNestedGuest {
     .copy = (c)                                    \
 }
 
+#define GSBE_NESTED_MACHINE_DW(i, f)  {                             \
+        .id = (i),                                                  \
+        .size = 8,                                                  \
+        .location = get_machine_ptr,                                \
+        .offset = offsetof(struct SpaprMachineStateNested, f),     \
+        .copy = copy_state_8to8,                                    \
+        .mask = HVMASK_DEFAULT                                      \
+}
+
 #define GSBE_NESTED(i, sz, f, c) {                             \
     .id = (i),                                                 \
     .size = (sz),                                              \
@@ -509,9 +562,11 @@ struct guest_state_element_type {
     uint16_t id;
     int size;
 #define GUEST_STATE_ELEMENT_TYPE_FLAG_GUEST_WIDE 0x1
-#define GUEST_STATE_ELEMENT_TYPE_FLAG_READ_ONLY  0x2
+#define GUEST_STATE_ELEMENT_TYPE_FLAG_HOST_WIDE 0x2
+#define GUEST_STATE_ELEMENT_TYPE_FLAG_READ_ONLY 0x4
    uint16_t flags;
-    void *(*location)(SpaprMachineStateNestedGuest *, target_ulong);
+   void *(*location)(struct SpaprMachineState *, SpaprMachineStateNestedGuest *,
+                     target_ulong);
     size_t offset;
     void (*copy)(void *, void *, bool);
     uint64_t mask;