[XEN PATCH v7 18/20] xen/arm: ffa: support sharing memory

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Adds support for a guest to share memory with an SP using FFA_MEM_SHARE
and FFA_MEM_RECLAIM. Only small memory regions can be shared using a
single call to FFA_MEM_SHARE are supported.

A memory region that doesn't need to be shared any longer can be
reclaimed with FFA_MEM_RECLAIM once the SP doesn't use it any longer.
This is checked by the SPMC and not in control of the mediator.

With this commit we have a FF-A version 1.1 [1] mediator able to
communicate with a Secure Partition in secure world using shared memory.
The secure world must use FF-A version 1.1, but the guest is free to use
version 1.0 or version 1.1.

Adds a check that the SP supports the needed FF-A features
FFA_MEM_SHARE_64 or FFA_MEM_SHARE_32.

[1] https://developer.arm.com/documentation/den0077/latest
Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
---
 xen/arch/arm/tee/ffa.c | 491 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 491 insertions(+)

diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
index 94c90b252454..cdc286caf62c 100644
--- a/xen/arch/arm/tee/ffa.c
+++ b/xen/arch/arm/tee/ffa.c
@@ -270,6 +270,38 @@ struct ffa_mem_transaction_1_1 {
     uint8_t reserved[12];
 };
 
+/* Calculate offset of struct ffa_mem_access from start of buffer */
+#define MEM_ACCESS_OFFSET(access_idx) \
+    ( sizeof(struct ffa_mem_transaction_1_1) + \
+      ( access_idx ) * sizeof(struct ffa_mem_access) )
+
+/* Calculate offset of struct ffa_mem_region from start of buffer */
+#define REGION_OFFSET(access_count, region_idx) \
+    ( MEM_ACCESS_OFFSET(access_count) + \
+      ( region_idx ) * sizeof(struct ffa_mem_region) )
+
+/* Calculate offset of struct ffa_address_range from start of buffer */
+#define ADDR_RANGE_OFFSET(access_count, region_count, range_idx) \
+    ( REGION_OFFSET(access_count, region_count) + \
+      ( range_idx ) * sizeof(struct ffa_address_range) )
+
+/*
+ * The parts needed from struct ffa_mem_transaction_1_0 or struct
+ * ffa_mem_transaction_1_1, used to provide an abstraction of difference in
+ * data structures between version 1.0 and 1.1. This is just an internal
+ * interface and can be changed without changing any ABI.
+ */
+struct ffa_mem_transaction_x {
+    uint16_t sender_id;
+    uint8_t mem_reg_attr;
+    uint8_t flags;
+    uint8_t mem_access_size;
+    uint8_t mem_access_count;
+    uint16_t mem_access_offs;
+    uint64_t global_handle;
+    uint64_t tag;
+};
+
 /* Endpoint RX/TX descriptor */
 struct ffa_endpoint_rxtx_descriptor_1_0 {
     uint16_t sender_id;
@@ -294,8 +326,20 @@ struct ffa_ctx {
     uint32_t guest_vers;
     bool tx_is_mine;
     bool interrupted;
+    struct list_head shm_list;
+    unsigned int shm_count;
     spinlock_t lock;
 };
+
+struct ffa_shm_mem {
+    struct list_head list;
+    uint16_t sender_id;
+    uint16_t ep_id;     /* endpoint, the one lending */
+    uint64_t handle;    /* FFA_HANDLE_INVALID if not set yet */
+    unsigned int page_count;
+    struct page_info *pages[];
+};
+
 /* Negotiated FF-A version to use with the SPMC */
 static uint32_t ffa_version __ro_after_init;
 
@@ -310,6 +354,8 @@ static unsigned int subscr_vm_destroyed_count __read_mostly;
  *
  * ffa_page_count is the number of pages used in each of these buffers.
  *
+ * The TX buffer is protected from concurrent usage with ffa_tx_buffer_lock.
+ *
  * The RX buffer is protected from concurrent usage with ffa_rx_buffer_lock.
  * Note that the SPMC is also tracking the ownership of our RX buffer so
  * for calls which uses our RX buffer to deliver a result we must call
@@ -319,6 +365,7 @@ static void *ffa_rx __read_mostly;
 static void *ffa_tx __read_mostly;
 static unsigned int ffa_page_count __read_mostly;
 static DEFINE_SPINLOCK(ffa_rx_buffer_lock);
+static DEFINE_SPINLOCK(ffa_tx_buffer_lock);
 
 static bool ffa_get_version(uint32_t *vers)
 {
@@ -429,6 +476,42 @@ static int32_t ffa_rx_release(void)
     return ffa_simple_call(FFA_RX_RELEASE, 0, 0, 0, 0);
 }
 
+static int32_t ffa_mem_share(uint32_t tot_len, uint32_t frag_len,
+                             register_t addr, uint32_t pg_count,
+                             uint64_t *handle)
+{
+    struct arm_smccc_1_2_regs arg = {
+        .a0 = FFA_MEM_SHARE_32,
+        .a1 = tot_len,
+        .a2 = frag_len,
+        .a3 = addr,
+        .a4 = pg_count,
+    };
+    struct arm_smccc_1_2_regs resp;
+
+    if ( IS_ENABLED(CONFIG_ARM_64) )
+        arg.a0 = FFA_MEM_SHARE_64;
+
+    arm_smccc_1_2_smc(&arg, &resp);
+
+    switch ( resp.a0 )
+    {
+    case FFA_ERROR:
+        if ( resp.a2 )
+            return resp.a2;
+        else
+            return FFA_RET_NOT_SUPPORTED;
+    case FFA_SUCCESS_32:
+        *handle = regpair_to_uint64(resp.a3, resp.a2);
+        return FFA_RET_OK;
+    case FFA_MEM_FRAG_RX:
+        *handle = regpair_to_uint64(resp.a2, resp.a1);
+        return resp.a3;
+    default:
+        return FFA_RET_NOT_SUPPORTED;
+    }
+}
+
 static int32_t ffa_direct_req_send_vm(uint16_t sp_id, uint16_t vm_id,
                                       uint8_t msg)
 {
@@ -757,6 +840,404 @@ out:
              resp.a4 & mask, resp.a5 & mask, resp.a6 & mask, resp.a7 & mask);
 }
 
+/*
+ * Gets all page and assigns them to the supplied shared memory object. If
+ * this function fails then the caller is still expected to call
+ * put_shm_pages() as a cleanup.
+ */
+static int get_shm_pages(struct domain *d, struct ffa_shm_mem *shm,
+                         const struct ffa_address_range *range,
+                         uint32_t range_count, unsigned int start_page_idx,
+                         unsigned int *last_page_idx)
+{
+    unsigned int pg_idx = start_page_idx;
+    gfn_t gfn;
+    unsigned int n;
+    unsigned int m;
+    p2m_type_t t;
+    uint64_t addr;
+
+    for ( n = 0; n < range_count; n++ )
+    {
+        for ( m = 0; m < range[n].page_count; m++ )
+        {
+            if ( pg_idx >= shm->page_count )
+                return FFA_RET_INVALID_PARAMETERS;
+
+            addr = read_atomic(&range[n].address);
+            gfn = gaddr_to_gfn(addr + m * FFA_PAGE_SIZE);
+            shm->pages[pg_idx] = get_page_from_gfn(d, gfn_x(gfn), &t,
+                                                  P2M_ALLOC);
+            if ( !shm->pages[pg_idx] )
+                return FFA_RET_DENIED;
+            pg_idx++;
+            /* Only normal RAM for now */
+            if ( !p2m_is_ram(t) )
+                return FFA_RET_DENIED;
+        }
+    }
+
+    *last_page_idx = pg_idx;
+
+    return FFA_RET_OK;
+}
+
+static void put_shm_pages(struct ffa_shm_mem *shm)
+{
+    unsigned int n;
+
+    for ( n = 0; n < shm->page_count && shm->pages[n]; n++ )
+    {
+        put_page(shm->pages[n]);
+        shm->pages[n] = NULL;
+    }
+}
+
+static struct ffa_shm_mem *alloc_ffa_shm_mem(struct ffa_ctx *ctx,
+                                             unsigned int page_count)
+{
+    struct ffa_shm_mem *shm;
+
+    if ( page_count >= FFA_MAX_SHM_PAGE_COUNT ||
+         ctx->shm_count >= FFA_MAX_SHM_COUNT )
+        return NULL;
+
+    shm = xzalloc_flex_struct(struct ffa_shm_mem, pages, page_count);
+    if ( shm )
+    {
+        ctx->shm_count++;
+        shm->page_count = page_count;
+    }
+
+    return shm;
+}
+
+static void free_ffa_shm_mem(struct ffa_ctx *ctx, struct ffa_shm_mem *shm)
+{
+    if ( shm ) {
+        ASSERT(ctx->shm_count > 0);
+        ctx->shm_count--;
+        put_shm_pages(shm);
+        xfree(shm);
+    }
+}
+
+static void init_range(struct ffa_address_range *addr_range,
+                       paddr_t pa)
+{
+    memset(addr_range, 0, sizeof(*addr_range));
+    addr_range->address = pa;
+    addr_range->page_count = 1;
+}
+
+/*
+ * This function uses the ffa_tx buffer to transmit the memory transaction
+ * descriptor. The function depends ffa_tx_buffer_lock to be used to guard
+ * the buffer from concurrent use.
+ */
+static int share_shm(struct ffa_shm_mem *shm)
+{
+    const uint32_t max_frag_len = ffa_page_count * FFA_PAGE_SIZE;
+    struct ffa_mem_access *mem_access_array;
+    struct ffa_mem_transaction_1_1 *descr;
+    struct ffa_address_range *addr_range;
+    struct ffa_mem_region *region_descr;
+    const unsigned int region_count = 1;
+    void *buf = ffa_tx;
+    uint32_t frag_len;
+    uint32_t tot_len;
+    paddr_t last_pa;
+    unsigned int n;
+    paddr_t pa;
+
+    ASSERT(spin_is_locked(&ffa_tx_buffer_lock));
+    if ( !shm->page_count )
+    {
+        ASSERT_UNREACHABLE();
+        return FFA_RET_INVALID_PARAMETERS;
+    }
+
+    descr = buf;
+    memset(descr, 0, sizeof(*descr));
+    descr->sender_id = shm->sender_id;
+    descr->global_handle = shm->handle;
+    descr->mem_reg_attr = FFA_NORMAL_MEM_REG_ATTR;
+    descr->mem_access_count = 1;
+    descr->mem_access_size = sizeof(*mem_access_array);
+    descr->mem_access_offs = MEM_ACCESS_OFFSET(0);
+
+    mem_access_array = buf + descr->mem_access_offs;
+    memset(mem_access_array, 0, sizeof(*mem_access_array));
+    mem_access_array[0].access_perm.endpoint_id = shm->ep_id;
+    mem_access_array[0].access_perm.perm = FFA_MEM_ACC_RW;
+    mem_access_array[0].region_offs = REGION_OFFSET(descr->mem_access_count, 
0);
+
+    region_descr = buf + mem_access_array[0].region_offs;
+    memset(region_descr, 0, sizeof(*region_descr));
+    region_descr->total_page_count = shm->page_count;
+
+    region_descr->address_range_count = 1;
+    last_pa = page_to_maddr(shm->pages[0]);
+    for ( n = 1; n < shm->page_count; last_pa = pa, n++ )
+    {
+        pa = page_to_maddr(shm->pages[n]);
+        if ( last_pa + FFA_PAGE_SIZE == pa )
+            continue;
+        region_descr->address_range_count++;
+    }
+
+    tot_len = ADDR_RANGE_OFFSET(descr->mem_access_count, region_count,
+                                region_descr->address_range_count);
+    if ( tot_len > max_frag_len )
+        return FFA_RET_NOT_SUPPORTED;
+
+    addr_range = region_descr->address_range_array;
+    frag_len = ADDR_RANGE_OFFSET(descr->mem_access_count, region_count, 1);
+    last_pa = page_to_maddr(shm->pages[0]);
+    init_range(addr_range, last_pa);
+    for ( n = 1; n < shm->page_count; last_pa = pa, n++ )
+    {
+        pa = page_to_maddr(shm->pages[n]);
+        if ( last_pa + FFA_PAGE_SIZE == pa )
+        {
+            addr_range->page_count++;
+            continue;
+        }
+
+        frag_len += sizeof(*addr_range);
+        addr_range++;
+        init_range(addr_range, pa);
+    }
+
+    return ffa_mem_share(tot_len, frag_len, 0, 0, &shm->handle);
+}
+
+static int read_mem_transaction(uint32_t ffa_vers, const void *buf, size_t 
blen,
+                                struct ffa_mem_transaction_x *trans)
+{
+    uint16_t mem_reg_attr;
+    uint32_t flags;
+    uint32_t count;
+    uint32_t offs;
+    uint32_t size;
+
+    if ( ffa_vers >= FFA_VERSION_1_1 )
+    {
+        const struct ffa_mem_transaction_1_1 *descr;
+
+        if ( blen < sizeof(*descr) )
+            return FFA_RET_INVALID_PARAMETERS;
+
+        descr = buf;
+        trans->sender_id = descr->sender_id;
+        mem_reg_attr = descr->mem_reg_attr;
+        flags = descr->flags;
+        trans->global_handle = descr->global_handle;
+        trans->tag = descr->tag;
+
+        count = descr->mem_access_count;
+        size = descr->mem_access_size;
+        offs = descr->mem_access_offs;
+    }
+    else
+    {
+        const struct ffa_mem_transaction_1_0 *descr;
+
+        if ( blen < sizeof(*descr) )
+            return FFA_RET_INVALID_PARAMETERS;
+
+        descr = buf;
+        trans->sender_id = descr->sender_id;
+        mem_reg_attr = descr->mem_reg_attr;
+        flags = descr->flags;
+        trans->global_handle = descr->global_handle;
+        trans->tag = descr->tag;
+
+        count = descr->mem_access_count;
+        size = sizeof(struct ffa_mem_access);
+        offs = offsetof(struct ffa_mem_transaction_1_0, mem_access_array);
+    }
+    /*
+     * Make sure that "descr" which is shared with the guest isn't accessed
+     * again after this point.
+     */
+    barrier();
+
+    /*
+     * We're doing a rough check to see that no information is lost when
+     * tranfering the values into a struct ffa_mem_transaction_x below. The
+     * fields in struct ffa_mem_transaction_x are wide enough to hold any
+     * valid value so being out of range means that something is wrong.
+     */
+    if ( mem_reg_attr > UINT8_MAX || flags > UINT8_MAX || size > UINT8_MAX ||
+        count > UINT8_MAX || offs > UINT16_MAX )
+        return FFA_RET_INVALID_PARAMETERS;
+
+    /* Check that the endpoint memory access descriptor array fits */
+    if ( size * count + offs > blen )
+        return FFA_RET_INVALID_PARAMETERS;
+
+    trans->mem_reg_attr = mem_reg_attr;
+    trans->flags = flags;
+    trans->mem_access_size = size;
+    trans->mem_access_count = count;
+    trans->mem_access_offs = offs;
+
+    return 0;
+}
+
+static void handle_mem_share(struct cpu_user_regs *regs)
+{
+    uint32_t tot_len = get_user_reg(regs, 1);
+    uint32_t frag_len = get_user_reg(regs, 2);
+    uint64_t addr = get_user_reg(regs, 3);
+    uint32_t page_count = get_user_reg(regs, 4);
+    const struct ffa_mem_region *region_descr;
+    const struct ffa_mem_access *mem_access;
+    struct ffa_mem_transaction_x trans;
+    struct domain *d = current->domain;
+    struct ffa_ctx *ctx = d->arch.tee;
+    struct ffa_shm_mem *shm = NULL;
+    unsigned int last_page_idx = 0;
+    register_t handle_hi = 0;
+    register_t handle_lo = 0;
+    int ret = FFA_RET_DENIED;
+    uint32_t range_count;
+    uint32_t region_offs;
+
+    /*
+     * We're only accepting memory transaction descriptors via the rx/tx
+     * buffer.
+     */
+    if ( addr )
+    {
+        ret = FFA_RET_NOT_SUPPORTED;
+        goto out_set_ret;
+    }
+
+    /* Check that fragment length doesn't exceed total length */
+    if ( frag_len > tot_len )
+    {
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out_set_ret;
+    }
+
+    /* We currently only support a single fragment */
+    if ( frag_len != tot_len )
+    {
+        ret = FFA_RET_NOT_SUPPORTED;
+        goto out_set_ret;
+    }
+
+    spin_lock(&ctx->lock);
+
+    if ( frag_len > ctx->page_count * FFA_PAGE_SIZE )
+        goto out_unlock;
+
+    if ( !ffa_page_count )
+    {
+        ret = FFA_RET_NO_MEMORY;
+        goto out_unlock;
+    }
+
+    ret = read_mem_transaction(ctx->guest_vers, ctx->tx, frag_len, &trans);
+    if ( ret )
+        goto out_unlock;
+
+    if ( trans.mem_reg_attr != FFA_NORMAL_MEM_REG_ATTR )
+    {
+        ret = FFA_RET_NOT_SUPPORTED;
+        goto out_unlock;
+    }
+
+    /* Only supports sharing it with one SP for now */
+    if ( trans.mem_access_count != 1 )
+    {
+        ret = FFA_RET_NOT_SUPPORTED;
+        goto out_unlock;
+    }
+
+    if ( trans.sender_id != get_vm_id(d) )
+    {
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out_unlock;
+    }
+
+    /* Check that it fits in the supplied data */
+    if ( trans.mem_access_offs + trans.mem_access_size > frag_len )
+        goto out_unlock;
+
+    mem_access = ctx->tx + trans.mem_access_offs;
+    if ( read_atomic(&mem_access->access_perm.perm) != FFA_MEM_ACC_RW )
+    {
+        ret = FFA_RET_NOT_SUPPORTED;
+        goto out_unlock;
+    }
+
+    region_offs = read_atomic(&mem_access->region_offs);
+    if ( sizeof(*region_descr) + region_offs > frag_len )
+    {
+        ret = FFA_RET_NOT_SUPPORTED;
+        goto out_unlock;
+    }
+
+    region_descr = ctx->tx + region_offs;
+    range_count = read_atomic(&region_descr->address_range_count);
+    page_count = read_atomic(&region_descr->total_page_count);
+
+    shm = alloc_ffa_shm_mem(ctx, page_count);
+    if ( !shm )
+    {
+        ret = FFA_RET_NO_MEMORY;
+        goto out_unlock;
+    }
+    shm->sender_id = trans.sender_id;
+    shm->ep_id = read_atomic(&mem_access->access_perm.endpoint_id);
+
+    /*
+     * Check that the Composite memory region descriptor fits.
+     */
+    if ( sizeof(*region_descr) + region_offs +
+         range_count * sizeof(struct ffa_address_range) > frag_len )
+    {
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out;
+    }
+
+    ret = get_shm_pages(d, shm, region_descr->address_range_array, range_count,
+                        0, &last_page_idx);
+    if ( ret )
+        goto out;
+    if ( last_page_idx != shm->page_count )
+    {
+        ret = FFA_RET_INVALID_PARAMETERS;
+        goto out;
+    }
+
+    /* Note that share_shm() uses our tx buffer */
+    spin_lock(&ffa_tx_buffer_lock);
+    ret = share_shm(shm);
+    spin_unlock(&ffa_tx_buffer_lock);
+    if ( ret )
+        goto out;
+
+    list_add_tail(&shm->list, &ctx->shm_list);
+
+    uint64_to_regpair(&handle_hi, &handle_lo, shm->handle);
+
+out:
+    if ( ret )
+        free_ffa_shm_mem(ctx, shm);
+out_unlock:
+    spin_unlock(&ctx->lock);
+
+out_set_ret:
+    if ( ret == 0)
+            set_regs_success(regs, handle_lo, handle_hi);
+    else
+            set_regs_error(regs, ret);
+}
+
 static bool ffa_handle_call(struct cpu_user_regs *regs)
 {
     uint32_t fid = get_user_reg(regs, 0);
@@ -818,6 +1299,12 @@ static bool ffa_handle_call(struct cpu_user_regs *regs)
 #endif
         handle_msg_send_direct_req(regs, fid);
         return true;
+    case FFA_MEM_SHARE_32:
+#ifdef CONFIG_ARM_64
+    case FFA_MEM_SHARE_64:
+#endif
+        handle_mem_share(regs);
+        return true;
 
     default:
         gprintk(XENLOG_ERR, "ffa: unhandled fid 0x%x\n", fid);
@@ -857,6 +1344,8 @@ static int ffa_domain_init(struct domain *d)
         }
     }
 
+    INIT_LIST_HEAD(&ctx->shm_list);
+
     d->arch.tee = ctx;
 
     return 0;
@@ -1012,11 +1501,13 @@ static bool ffa_probe(void)
          !check_mandatory_feature(FFA_RX_RELEASE) ||
 #ifdef CONFIG_ARM_64
          !check_mandatory_feature(FFA_RXTX_MAP_64) ||
+         !check_mandatory_feature(FFA_MEM_SHARE_64) ||
 #endif
 #ifdef CONFIG_ARM_32
          !check_mandatory_feature(FFA_RXTX_MAP_32) ||
 #endif
          !check_mandatory_feature(FFA_RXTX_UNMAP) ||
+         !check_mandatory_feature(FFA_MEM_SHARE_32) ||
          !check_mandatory_feature(FFA_MSG_SEND_DIRECT_REQ_32) )
         return false;
 
-- 
2.34.1