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Re: [Xen-devel] [PATCH v2 08/13] optee: add support for RPC SHM buffers
Hi Julien,
On 10.09.18 16:01, Julien Grall wrote:
Hi Volodymyr,
On 03/09/18 17:54, Volodymyr Babchuk wrote:
OP-TEE usually uses the same idea with command buffers (see
previous commit) to issue RPC requests. Problem is that initially
it has no buffer, where it can write request. So the first RPC
request it makes is special: it requests NW to allocate shared
buffer for other RPC requests. Usually this buffer is allocated
only once for every OP-TEE thread and it remains allocated all
the time until shutdown.
Mediator needs to pin this buffer(s) to make sure that domain can't
transfer it to someone else. Also it should be mapped into XEN
address space, because mediator needs to check responses from
guests.
Can you explain why you always need to keep the shared buffer mapped in
Xen? Why not using access_guest_memory_by_ipa every time you want to get
information from the guest?
Sorry, I just didn't know about this mechanism. But for performance reasons,
I'd like to keep this buffers always mapped. You see, RPC returns are
very frequent (for every IRQ, actually). So I think, it will be costly
to map/unmap this buffer every time.
Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
---
xen/arch/arm/tee/optee.c | 121
++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 119 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/tee/optee.c b/xen/arch/arm/tee/optee.c
index 1008eba..6d6b51d 100644
--- a/xen/arch/arm/tee/optee.c
+++ b/xen/arch/arm/tee/optee.c
@@ -21,6 +21,7 @@
#include <asm/tee/optee_smc.h>
#define MAX_STD_CALLS 16
+#define MAX_RPC_SHMS 16
/*
* Call context. OP-TEE can issue multiple RPC returns during one call.
@@ -35,11 +36,22 @@ struct std_call_ctx {
int rpc_op;
};
+/* Pre-allocated SHM buffer for RPC commands */
+struct shm_rpc {
+ struct list_head list;
+ struct optee_msg_arg *guest_arg;
+ struct page *guest_page;
+ mfn_t guest_mfn;
+ uint64_t cookie;
+};
+
struct domain_ctx {
struct list_head list;
struct list_head call_ctx_list;
+ struct list_head shm_rpc_list;
struct domain *domain;
atomic_t call_ctx_count;
+ atomic_t shm_rpc_count;
spinlock_t lock;
};
@@ -145,8 +157,10 @@ static int optee_enable(struct domain *d)
ctx->domain = d;
INIT_LIST_HEAD(&ctx->call_ctx_list);
+ INIT_LIST_HEAD(&ctx->shm_rpc_list);
atomic_set(&ctx->call_ctx_count, 0);
+ atomic_set(&ctx->shm_rpc_count, 0);
spin_lock_init(&ctx->lock);
spin_lock(&domain_ctx_list_lock);
@@ -256,11 +270,81 @@ static struct std_call_ctx *find_call_ctx(struct
domain_ctx *ctx, int thread_id)
return NULL;
}
+static struct shm_rpc *allocate_and_map_shm_rpc(struct domain_ctx
*ctx, paddr_t gaddr,
I would prefer if you pass a gfn instead of the address here.
+ uint64_t cookie)
NIT: Indentation
+{
+ struct shm_rpc *shm_rpc;
+ int count;
+
+ count = atomic_add_unless(&ctx->shm_rpc_count, 1, MAX_RPC_SHMS);
+ if ( count == MAX_RPC_SHMS )
+ return NULL;
+
+ shm_rpc = xzalloc(struct shm_rpc);
+ if ( !shm_rpc )
+ goto err;
+
+ shm_rpc->guest_mfn = lookup_and_pin_guest_ram_addr(gaddr, NULL);
+
+ if ( mfn_eq(shm_rpc->guest_mfn, INVALID_MFN) )
+ goto err;
+
+ shm_rpc->guest_arg = map_domain_page_global(shm_rpc->guest_mfn);
+ if ( !shm_rpc->guest_arg )
+ {
+ gprintk(XENLOG_INFO, "Could not map domain page\n");
You don't unpin the guest page if Xen can't map the page.
+ goto err;
+ }
+ shm_rpc->cookie = cookie;
+
+ spin_lock(&ctx->lock);
+ list_add_tail(&shm_rpc->list, &ctx->shm_rpc_list);
+ spin_unlock(&ctx->lock);
+
+ return shm_rpc;
+
+err:
+ atomic_dec(&ctx->shm_rpc_count);
+ xfree(shm_rpc);
+ return NULL;
+}
+
+static void free_shm_rpc(struct domain_ctx *ctx, uint64_t cookie)
+{
+ struct shm_rpc *shm_rpc;
+ bool found = false;
+
+ spin_lock(&ctx->lock);
+
+ list_for_each_entry( shm_rpc, &ctx->shm_rpc_list, list )
+ {
+ if ( shm_rpc->cookie == cookie )
What does guarantee you the cookie will be uniq?
Normal World guarantees. This is the part of the protocol.
+ {
+ found = true;
+ list_del(&shm_rpc->list);
+ break;
+ }
+ }
+ spin_unlock(&ctx->lock);
At this point you have a shm_rpc in hand to free. But what does
guarantee you no-one will use it?
This is valid point. I'll revisit this part of the code, thank you.
Looks like I need some refcount there.
+
+ if ( !found ) {
+ return;
+ }
No need for the {} in a one-liner.
+
+ if ( shm_rpc->guest_arg ) {
Coding style:
if ( ... )
{
+ unpin_guest_ram_addr(shm_rpc->guest_mfn);
+ unmap_domain_page_global(shm_rpc->guest_arg);
+ }
+
+ xfree(shm_rpc);
+}
+
static void optee_domain_destroy(struct domain *d)
{
struct arm_smccc_res resp;
struct domain_ctx *ctx;
struct std_call_ctx *call, *call_tmp;
+ struct shm_rpc *shm_rpc, *shm_rpc_tmp;
bool found = false;
/* At this time all domain VCPUs should be stopped */
@@ -290,7 +374,11 @@ static void optee_domain_destroy(struct domain *d)
list_for_each_entry_safe( call, call_tmp, &ctx->call_ctx_list,
list )
free_std_call_ctx(ctx, call);
+ list_for_each_entry_safe( shm_rpc, shm_rpc_tmp,
&ctx->shm_rpc_list, list )
+ free_shm_rpc(ctx, shm_rpc->cookie);
+
ASSERT(!atomic_read(&ctx->call_ctx_count));
+ ASSERT(!atomic_read(&ctx->shm_rpc_count));
xfree(ctx);
}
@@ -452,6 +540,32 @@ out:
return ret;
}
+static void handle_rpc_func_alloc(struct domain_ctx *ctx,
+ struct cpu_user_regs *regs)
+{
+ paddr_t ptr = get_user_reg(regs, 1) << 32 | get_user_reg(regs, 2);
+
+ if ( ptr & (OPTEE_MSG_NONCONTIG_PAGE_SIZE - 1) )
+ gprintk(XENLOG_WARNING, "Domain returned invalid RPC command
buffer\n");
+
+ if ( ptr ) {
+ uint64_t cookie = get_user_reg(regs, 4) << 32 |
get_user_reg(regs, 5);
+ struct shm_rpc *shm_rpc;
+
+ shm_rpc = allocate_and_map_shm_rpc(ctx, ptr, cookie);
+ if ( !shm_rpc )
+ {
+ gprintk(XENLOG_WARNING, "Failed to allocate shm_rpc
object\n");
+ ptr = 0;
+ }
+ else
+ ptr = mfn_to_maddr(shm_rpc->guest_mfn);
+
+ set_user_reg(regs, 1, ptr >> 32);
+ set_user_reg(regs, 2, ptr & 0xFFFFFFFF);
+ }
+}
+
static bool handle_rpc(struct domain_ctx *ctx, struct cpu_user_regs
*regs)
{
struct std_call_ctx *call;
@@ -465,11 +579,14 @@ static bool handle_rpc(struct domain_ctx *ctx,
struct cpu_user_regs *regs)
switch ( call->rpc_op ) {
case OPTEE_SMC_RPC_FUNC_ALLOC:
- /* TODO: Add handling */
+ handle_rpc_func_alloc(ctx, regs);
break;
case OPTEE_SMC_RPC_FUNC_FREE:
- /* TODO: Add handling */
+ {
+ uint64_t cookie = get_user_reg(regs, 1) << 32 |
get_user_reg(regs, 2);
Newline here.
+ free_shm_rpc(ctx, cookie);
It feels quite suspicious to free the memory in Xen before calling
OP-TEE. I think this need to be done afterwards.
No, it is OP-TEE asked to free buffer. This function is called, when NW
returns from the RPC. So at this moment NW freed the buffer.
break;
+ }
case OPTEE_SMC_RPC_FUNC_FOREIGN_INTR:
break;
case OPTEE_SMC_RPC_FUNC_CMD:
Cheers,
--
Volodymyr Babchuk
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