i386/tdx: Track RAM entries for TDX VM

The RAM of TDX VM can be classified into two types:

 - TDX_RAM_UNACCEPTED: default type of TDX memory, which needs to be
   accepted by TDX guest before it can be used and will be all-zeros
   after being accepted.

 - TDX_RAM_ADDED: the RAM that is ADD'ed to TD guest before running, and
   can be used directly. E.g., TD HOB and TEMP MEM that needed by TDVF.

Maintain TdxRamEntries[] which grabs the initial RAM info from e820 table
and mark each RAM range as default type TDX_RAM_UNACCEPTED.

Then turn the range of TD HOB and TEMP MEM to TDX_RAM_ADDED since these
ranges will be ADD'ed before TD runs and no need to be accepted runtime.

The TdxRamEntries[] are later used to setup the memory TD resource HOB
that passes memory info from QEMU to TDVF.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-22-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/kvm/tdx.c

@@ -18,6 +18,7 @@
 #include "crypto/hash.h"
 #include "system/system.h"
 
+#include "hw/i386/e820_memory_layout.h"
 #include "hw/i386/tdvf.h"
 #include "hw/i386/x86.h"
 #include "kvm_i386.h"
@@ -146,11 +147,110 @@ void tdx_set_tdvf_region(MemoryRegion *tdvf_mr)
     tdx_guest->tdvf_mr = tdvf_mr;
 }
 
+static void tdx_add_ram_entry(uint64_t address, uint64_t length,
+                              enum TdxRamType type)
+{
+    uint32_t nr_entries = tdx_guest->nr_ram_entries;
+    tdx_guest->ram_entries = g_renew(TdxRamEntry, tdx_guest->ram_entries,
+                                     nr_entries + 1);
+
+    tdx_guest->ram_entries[nr_entries].address = address;
+    tdx_guest->ram_entries[nr_entries].length = length;
+    tdx_guest->ram_entries[nr_entries].type = type;
+    tdx_guest->nr_ram_entries++;
+}
+
+static int tdx_accept_ram_range(uint64_t address, uint64_t length)
+{
+    uint64_t head_start, tail_start, head_length, tail_length;
+    uint64_t tmp_address, tmp_length;
+    TdxRamEntry *e;
+    int i = 0;
+
+    do {
+        if (i == tdx_guest->nr_ram_entries) {
+            return -1;
+        }
+
+        e = &tdx_guest->ram_entries[i++];
+    } while (address + length <= e->address || address >= e->address + e->length);
+
+    /*
+     * The to-be-accepted ram range must be fully contained by one
+     * RAM entry.
+     */
+    if (e->address > address ||
+        e->address + e->length < address + length) {
+        return -1;
+    }
+
+    if (e->type == TDX_RAM_ADDED) {
+        return 0;
+    }
+
+    tmp_address = e->address;
+    tmp_length = e->length;
+
+    e->address = address;
+    e->length = length;
+    e->type = TDX_RAM_ADDED;
+
+    head_length = address - tmp_address;
+    if (head_length > 0) {
+        head_start = tmp_address;
+        tdx_add_ram_entry(head_start, head_length, TDX_RAM_UNACCEPTED);
+    }
+
+    tail_start = address + length;
+    if (tail_start < tmp_address + tmp_length) {
+        tail_length = tmp_address + tmp_length - tail_start;
+        tdx_add_ram_entry(tail_start, tail_length, TDX_RAM_UNACCEPTED);
+    }
+
+    return 0;
+}
+
+static int tdx_ram_entry_compare(const void *lhs_, const void* rhs_)
+{
+    const TdxRamEntry *lhs = lhs_;
+    const TdxRamEntry *rhs = rhs_;
+
+    if (lhs->address == rhs->address) {
+        return 0;
+    }
+    if (le64_to_cpu(lhs->address) > le64_to_cpu(rhs->address)) {
+        return 1;
+    }
+    return -1;
+}
+
+static void tdx_init_ram_entries(void)
+{
+    unsigned i, j, nr_e820_entries;
+
+    nr_e820_entries = e820_get_table(NULL);
+    tdx_guest->ram_entries = g_new(TdxRamEntry, nr_e820_entries);
+
+    for (i = 0, j = 0; i < nr_e820_entries; i++) {
+        uint64_t addr, len;
+
+        if (e820_get_entry(i, E820_RAM, &addr, &len)) {
+            tdx_guest->ram_entries[j].address = addr;
+            tdx_guest->ram_entries[j].length = len;
+            tdx_guest->ram_entries[j].type = TDX_RAM_UNACCEPTED;
+            j++;
+        }
+    }
+    tdx_guest->nr_ram_entries = j;
+}
+
 static void tdx_finalize_vm(Notifier *notifier, void *unused)
 {
     TdxFirmware *tdvf = &tdx_guest->tdvf;
     TdxFirmwareEntry *entry;
 
+    tdx_init_ram_entries();
+
     for_each_tdx_fw_entry(tdvf, entry) {
         switch (entry->type) {
         case TDVF_SECTION_TYPE_BFV:
@@ -166,12 +266,21 @@ static void tdx_finalize_vm(Notifier *notifier, void *unused)
                              entry->type);
                 exit(1);
             }
+            if (tdx_accept_ram_range(entry->address, entry->size)) {
+                error_report("Failed to accept memory for TDVF section %d",
+                             entry->type);
+                qemu_ram_munmap(-1, entry->mem_ptr, entry->size);
+                exit(1);
+            }
             break;
         default:
             error_report("Unsupported TDVF section %d", entry->type);
             exit(1);
         }
     }
+
+    qsort(tdx_guest->ram_entries, tdx_guest->nr_ram_entries,
+          sizeof(TdxRamEntry), &tdx_ram_entry_compare);
 }
 
 static Notifier tdx_machine_done_notify = {

target/i386/kvm/tdx.h

@@ -20,6 +20,17 @@ typedef struct TdxGuestClass {
 /* TDX requires bus frequency 25MHz */
 #define TDX_APIC_BUS_CYCLES_NS 40
 
+enum TdxRamType {
+    TDX_RAM_UNACCEPTED,
+    TDX_RAM_ADDED,
+};
+
+typedef struct TdxRamEntry {
+    uint64_t address;
+    uint64_t length;
+    enum TdxRamType type;
+} TdxRamEntry;
+
 typedef struct TdxGuest {
     X86ConfidentialGuest parent_obj;
 
@@ -34,6 +45,9 @@ typedef struct TdxGuest {
 
     MemoryRegion *tdvf_mr;
     TdxFirmware tdvf;
+
+    uint32_t nr_ram_entries;
+    TdxRamEntry *ram_entries;
 } TdxGuest;
 
 #ifdef CONFIG_TDX