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Subject[PATCH v12 10/13] x86/sgx: sgx_einit()
Date
From: Sean Christopherson <sean.j.christopherson@intel.com>

Implements function to perform ENCLS(EINIT) leaf function that initializes
an enclave, which can be used by a driver for running enclaves and VMMs.

Writing the LE hash MSRs is extraordinarily expensive, e.g. 3-4x slower
than normal MSRs, so we use a per-cpu cache to track the last known value
of the MSRs to avoid unnecessarily writing the MSRs with the current value.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/sgx.h | 2 ++
arch/x86/kernel/cpu/intel_sgx.c | 46 +++++++++++++++++++++++++++++++++
2 files changed, 48 insertions(+)

diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
index 4f5f32b37b5d..bc09b4576d68 100644
--- a/arch/x86/include/asm/sgx.h
+++ b/arch/x86/include/asm/sgx.h
@@ -215,6 +215,8 @@ void *sgx_get_page(struct sgx_epc_page *ptr);
void sgx_put_page(void *epc_page_ptr);
struct page *sgx_get_backing(struct file *file, pgoff_t index);
void sgx_put_backing(struct page *backing_page, bool write);
+int sgx_einit(struct sgx_sigstruct *sigstruct, struct sgx_einittoken *token,
+ struct sgx_epc_page *secs_page, u64 le_pubkey_hash[4]);

#define SGX_FN(name, params...) \
{ \
diff --git a/arch/x86/kernel/cpu/intel_sgx.c b/arch/x86/kernel/cpu/intel_sgx.c
index b52bab8eff99..53dd91cb7a49 100644
--- a/arch/x86/kernel/cpu/intel_sgx.c
+++ b/arch/x86/kernel/cpu/intel_sgx.c
@@ -31,6 +31,12 @@ static int sgx_nr_epc_banks;
static struct task_struct *ksgxswapd_tsk;
static DECLARE_WAIT_QUEUE_HEAD(ksgxswapd_waitq);

+/*
+ * A cache for last known values of IA32_SGXLEPUBKEYHASHx MSRs. Cache entries
+ * are initialized when they are first used by sgx_einit().
+ */
+static DEFINE_PER_CPU(u64 [4], sgx_le_pubkey_hash_cache);
+
static void sgx_swap_cluster(void)
{
struct sgx_epc_page *cluster[SGX_NR_TO_SCAN + 1];
@@ -255,6 +261,46 @@ void sgx_put_backing(struct page *backing_page, bool write)
}
EXPORT_SYMBOL(sgx_put_backing);

+/**
+ * sgx_einit - EINIT an enclave with the appropriate LE pubkey hash
+ * @sigstruct: a pointer to the enclave's sigstruct
+ * @token: a pointer to the enclave's EINIT token
+ * @secs_page: a pointer to the enclave's SECS EPC page
+ * @le_pubkey_hash: the desired LE pubkey hash for EINIT
+ */
+int sgx_einit(struct sgx_sigstruct *sigstruct, struct sgx_einittoken *token,
+ struct sgx_epc_page *secs_page, u64 le_pubkey_hash[4])
+{
+ u64 __percpu *cache;
+ void *secs;
+ int i, ret;
+
+ secs = sgx_get_page(secs_page);
+
+ if (!sgx_lc_enabled) {
+ ret = __einit(sigstruct, token, secs);
+ goto out;
+ }
+
+ cache = per_cpu(sgx_le_pubkey_hash_cache, smp_processor_id());
+
+ preempt_disable();
+ for (i = 0; i < 4; i++) {
+ if (le_pubkey_hash[i] == cache[i])
+ continue;
+
+ wrmsrl(MSR_IA32_SGXLEPUBKEYHASH0 + i, le_pubkey_hash[i]);
+ cache[i] = le_pubkey_hash[i];
+ }
+ ret = __einit(sigstruct, token, secs);
+ preempt_enable();
+
+out:
+ sgx_put_page(secs);
+ return ret;
+}
+EXPORT_SYMBOL(sgx_einit);
+
static __init int sgx_init_epc_bank(unsigned long addr, unsigned long size,
unsigned long index,
struct sgx_epc_bank *bank)
--
2.17.1
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