xen/arm: Reduce struct membank size on static shared memory

Currently the memory footprint of the static shared memory feature
is impacting all the struct meminfo instances with memory space
that is not going to be used.

To solve this issue, rework the static shared memory extra
information linked to the memory bank to another structure,
struct shmem_membank_extra, and exploit the struct membank
padding to host a pointer to that structure in a union with the
enum membank_type, with this trick the 'struct membank' has the
same size with or without the static shared memory, given that
the 'type' and 'shmem_extra' are never used at the same time,
hence the 'struct membank' won't grow in size.

Afterwards, create a new structure 'struct shared_meminfo' which
has the same interface of 'struct meminfo', but requires less
banks, defined by the number in NR_SHMEM_BANKS, which is 32 at the
moment and should be enough for the current use cases, the value
might be increased in te future if needed.
Finally, this structure hosts also the extra information for the
static shared memory banks.
The fields 'bank' and 'extra' of this structure are meant to be
linked by the index (e.g. extra[idx] will have the information for
the bank[idx], for i=0..NR_SHMEM_BANKS), the convinient pointer
'shmem_extra' of 'struct membank' is then linked to the related
'extra' bank to ease the fruition when a function has access only
to the 'struct membanks common' of 'struct shared_meminfo'.

The last part of this work is to move the allocation of the
static shared memory banks from the 'reserved_mem' to a new
'shmem' member of the 'struct bootinfo'.
Change also the 'shm_mem' member type to be 'struct shared_meminfo'
in order to match the above changes and allow a memory space
reduction also in 'struct kernel_info'.

Now that the structure

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

xen/arch/arm/arm32/mmu/mm.c

@@ -8,6 +8,7 @@
 #include <xen/pfn.h>
 #include <asm/fixmap.h>
 #include <asm/static-memory.h>
+#include <asm/static-shmem.h>
 
 static unsigned long opt_xenheap_megabytes __initdata;
 integer_param("xenheap_megabytes", opt_xenheap_megabytes);
@@ -43,6 +44,9 @@ static paddr_t __init consider_modules(paddr_t s, paddr_t e,
                                        int first_mod)
 {
     const struct membanks *reserved_mem = bootinfo_get_reserved_mem();
+#ifdef CONFIG_STATIC_SHM
+    const struct membanks *shmem = bootinfo_get_shmem();
+#endif
     const struct bootmodules *mi = &bootinfo.modules;
     int i;
     int nr;
@@ -119,6 +123,25 @@ static paddr_t __init consider_modules(paddr_t s, paddr_t e,
             return consider_modules(s, r_s, size, align, i + 1);
         }
     }
+
+#ifdef CONFIG_STATIC_SHM
+    nr += reserved_mem->nr_banks;
+    for ( ; i - nr < shmem->nr_banks; i++ )
+    {
+        paddr_t r_s = shmem->bank[i - nr].start;
+        paddr_t r_e = r_s + shmem->bank[i - nr].size;
+
+        if ( s < r_e && r_s < e )
+        {
+            r_e = consider_modules(r_e, e, size, align, i + 1);
+            if ( r_e )
+                return r_e;
+
+            return consider_modules(s, r_s, size, align, i + 1);
+        }
+    }
+#endif
+
     return e;
 }
 
@@ -295,6 +318,7 @@ void __init setup_mm(void)
                        mfn_to_maddr(directmap_mfn_end));
 
     init_staticmem_pages();
+    init_sharedmem_pages();
 }
 
 /*

xen/arch/arm/arm64/mmu/mm.c

@@ -6,6 +6,7 @@
 
 #include <asm/setup.h>
 #include <asm/static-memory.h>
+#include <asm/static-shmem.h>
 
 /* Override macros from asm/page.h to make them work with mfn_t */
 #undef virt_to_mfn
@@ -236,6 +237,7 @@ void __init setup_mm(void)
     max_page = PFN_DOWN(ram_end);
 
     init_staticmem_pages();
+    init_sharedmem_pages();
 }
 
 /*

xen/arch/arm/bootfdt.c

@@ -511,6 +511,7 @@ static void __init early_print_info(void)
                mem_resv->bank[j].start,
                mem_resv->bank[j].start + mem_resv->bank[j].size - 1);
     }
+    early_print_info_shmem();
     printk("\n");
     for ( i = 0 ; i < cmds->nr_mods; i++ )
         printk("CMDLINE[%"PRIpaddr"]:%s %s\n", cmds->cmdline[i].start,

xen/arch/arm/domain_build.c

@@ -863,6 +863,7 @@ static int __init add_ext_regions(unsigned long s_gfn, unsigned long e_gfn,
  * regions we exclude every region assigned to Dom0 from the Host RAM:
  * - domain RAM
  * - reserved-memory
+ * - static shared memory
  * - grant table space
  */
 static int __init find_unallocated_memory(const struct kernel_info *kinfo,
@@ -872,6 +873,9 @@ static int __init find_unallocated_memory(const struct kernel_info *kinfo,
     const struct membanks *mem_banks[] = {
         kernel_info_get_mem(kinfo),
         bootinfo_get_reserved_mem(),
+#ifdef CONFIG_STATIC_SHM
+        bootinfo_get_shmem(),
+#endif
     };
     struct rangeset *unalloc_mem;
     paddr_t start, end;
@@ -903,6 +907,7 @@ static int __init find_unallocated_memory(const struct kernel_info *kinfo,
      * Exclude the following regions:
      * 1) Remove RAM assigned to Dom0
      * 2) Remove reserved memory
+     * 3) Remove static shared memory (when the feature is enabled)
      */
     for ( i = 0; i < ARRAY_SIZE(mem_banks); i++ )
         for ( j = 0; j < mem_banks[i]->nr_banks; j++ )

xen/arch/arm/include/asm/kernel.h

@@ -40,7 +40,7 @@ struct kernel_info {
     paddr_t unassigned_mem; /* RAM not (yet) assigned to a bank */
     struct meminfo mem;
 #ifdef CONFIG_STATIC_SHM
-    struct meminfo shm_mem;
+    struct shared_meminfo shm_mem;
 #endif
 
     /* kernel entry point */
@@ -83,7 +83,7 @@ struct kernel_info {
 #define kernel_info_get_mem(kinfo) (&(kinfo)->mem.common)
 
 #ifdef CONFIG_STATIC_SHM
-#define KERNEL_INFO_SHM_MEM_INIT .shm_mem.common.max_banks = NR_MEM_BANKS,
+#define KERNEL_INFO_SHM_MEM_INIT .shm_mem.common.max_banks = NR_SHMEM_BANKS,
 #else
 #define KERNEL_INFO_SHM_MEM_INIT
 #endif

xen/arch/arm/include/asm/setup.h

@@ -9,6 +9,7 @@
 #define MAX_FDT_SIZE SZ_2M
 
 #define NR_MEM_BANKS 256
+#define NR_SHMEM_BANKS 32
 
 #define MAX_MODULES 32 /* Current maximum useful modules */
 
@@ -46,14 +47,20 @@ enum membank_type {
 /* Indicates the maximum number of characters(\0 included) for shm_id */
 #define MAX_SHM_ID_LENGTH 16
 
+struct shmem_membank_extra {
+    char shm_id[MAX_SHM_ID_LENGTH];
+    unsigned int nr_shm_borrowers;
+};
+
 struct membank {
     paddr_t start;
     paddr_t size;
-    enum membank_type type;
+    union {
+        enum membank_type type;
 #ifdef CONFIG_STATIC_SHM
-    char shm_id[MAX_SHM_ID_LENGTH];
-    unsigned int nr_shm_borrowers;
+        struct shmem_membank_extra *shmem_extra;
 #endif
+    };
 };
 
 struct membanks {
@@ -67,6 +74,12 @@ struct meminfo {
     struct membank bank[NR_MEM_BANKS];
 };
 
+struct shared_meminfo {
+    struct membanks common;
+    struct membank bank[NR_SHMEM_BANKS];
+    struct shmem_membank_extra extra[NR_SHMEM_BANKS];
+};
+
 /*
  * The domU flag is set for kernels and ramdisks of "xen,domain" nodes.
  * The purpose of the domU flag is to avoid getting confused in
@@ -109,6 +122,9 @@ struct bootinfo {
     struct bootcmdlines cmdlines;
 #ifdef CONFIG_ACPI
     struct meminfo acpi;
+#endif
+#ifdef CONFIG_STATIC_SHM
+    struct shared_meminfo shmem;
 #endif
     bool static_heap;
 };
@@ -119,11 +135,18 @@ struct bootinfo {
 #define BOOTINFO_ACPI_INIT
 #endif
 
+#ifdef CONFIG_STATIC_SHM
+#define BOOTINFO_SHMEM_INIT .shmem.common.max_banks = NR_SHMEM_BANKS,
+#else
+#define BOOTINFO_SHMEM_INIT
+#endif
+
 #define BOOTINFO_INIT                               \
 {                                                   \
     .mem.common.max_banks = NR_MEM_BANKS,           \
     .reserved_mem.common.max_banks = NR_MEM_BANKS,  \
     BOOTINFO_ACPI_INIT                              \
+    BOOTINFO_SHMEM_INIT                             \
 }
 
 struct map_range_data
@@ -158,6 +181,18 @@ static inline struct membanks *bootinfo_get_acpi(void)
 }
 #endif
 
+#ifdef CONFIG_STATIC_SHM
+static inline struct membanks *bootinfo_get_shmem(void)
+{
+    return &bootinfo.shmem.common;
+}
+
+static inline struct shmem_membank_extra *bootinfo_get_shmem_extra(void)
+{
+    return bootinfo.shmem.extra;
+}
+#endif
+
 void copy_from_paddr(void *dst, paddr_t paddr, unsigned long len);
 
 size_t estimate_efi_size(unsigned int mem_nr_banks);

xen/arch/arm/include/asm/static-shmem.h

@@ -24,6 +24,10 @@ static inline int process_shm_chosen(struct domain *d,
 int process_shm_node(const void *fdt, int node, uint32_t address_cells,
                      uint32_t size_cells);
 
+void early_print_info_shmem(void);
+
+void init_sharedmem_pages(void);
+
 #else /* !CONFIG_STATIC_SHM */
 
 static inline int make_resv_memory_node(const struct kernel_info *kinfo,
@@ -51,6 +55,10 @@ static inline int process_shm_node(const void *fdt, int node,
     return -EINVAL;
 }
 
+static inline void early_print_info_shmem(void) {};
+
+static inline void init_sharedmem_pages(void) {};
+
 #endif /* CONFIG_STATIC_SHM */
 
 #endif /* __ASM_STATIC_SHMEM_H_ */

xen/arch/arm/setup.c

@@ -208,6 +208,9 @@ static void __init dt_unreserved_regions(paddr_t s, paddr_t e,
                                          unsigned int first)
 {
     const struct membanks *reserved_mem = bootinfo_get_reserved_mem();
+#ifdef CONFIG_STATIC_SHM
+    const struct membanks *shmem = bootinfo_get_shmem();
+#endif
     unsigned int i, nr;
     int rc;
 
@@ -258,6 +261,22 @@ static void __init dt_unreserved_regions(paddr_t s, paddr_t e,
         }
     }
 
+#ifdef CONFIG_STATIC_SHM
+    nr += reserved_mem->nr_banks;
+    for ( ; i - nr < shmem->nr_banks; i++ )
+    {
+        paddr_t r_s = shmem->bank[i - nr].start;
+        paddr_t r_e = r_s + shmem->bank[i - nr].size;
+
+        if ( s < r_e && r_s < e )
+        {
+            dt_unreserved_regions(r_e, e, cb, i + 1);
+            dt_unreserved_regions(s, r_s, cb, i + 1);
+            return;
+        }
+    }
+#endif
+
     cb(s, e);
 }
 
@@ -344,13 +363,17 @@ bool __init check_reserved_regions_overlap(paddr_t region_start,
         bootinfo_get_reserved_mem(),
 #ifdef CONFIG_ACPI
         bootinfo_get_acpi(),
+#endif
+#ifdef CONFIG_STATIC_SHM
+        bootinfo_get_shmem(),
 #endif
     };
     unsigned int i;
 
     /*
      * Check if input region is overlapping with reserved memory banks or
-     * ACPI EfiACPIReclaimMemory (when ACPI feature is enabled)
+     * ACPI EfiACPIReclaimMemory (when ACPI feature is enabled) or static
+     * shared memory banks (when static shared memory feature is enabled)
      */
     for ( i = 0; i < ARRAY_SIZE(mem_banks); i++ )
         if ( meminfo_overlap_check(mem_banks[i], region_start, region_size) )