From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DFE77C4332F for ; Mon, 17 Oct 2022 08:32:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230102AbiJQIc4 (ORCPT ); Mon, 17 Oct 2022 04:32:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230110AbiJQIcn (ORCPT ); Mon, 17 Oct 2022 04:32:43 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C5EB3FEF9 for ; Mon, 17 Oct 2022 01:32:41 -0700 (PDT) Received: from dggpeml500024.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4MrVc24CRyzHvsJ; Mon, 17 Oct 2022 16:32:34 +0800 (CST) Received: from huawei.com (10.44.134.232) by dggpeml500024.china.huawei.com (7.185.36.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 17 Oct 2022 16:32:08 +0800 From: Yunfeng Ye To: , , , , , CC: Subject: [PATCH 4/5] arm64: mm: Support ASID isolation feature Date: Mon, 17 Oct 2022 16:32:02 +0800 Message-ID: <20221017083203.3690346-5-yeyunfeng@huawei.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20221017083203.3690346-1-yeyunfeng@huawei.com> References: <20221017083203.3690346-1-yeyunfeng@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.44.134.232] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500024.china.huawei.com (7.185.36.10) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After a rollover, the global generation will be flushed, which will cause the process mm->context.id on all CPUs do not match the generation. Thus, the process will compete for the global spinlock lock to reallocate a new ASID and refresh the TLBs of all CPUs on context switch. This will lead to the increase of scheduling delay and TLB miss. In some delay-sensitive scenarios, for example, part of CPUs are isolated, only a limited number of processes are deployed to run on the isolated CPUs. In this case, we do not want these key processes to be affected by the rollover of ASID. An ASID isolation method can reduce interference. We divide the asid_generation into different domains, for example, HOUSEKEEPING and ISOLATION. Processes in different domains allocate ASID from the shared asid_map pool, then combine with the generation of local domain as the mm->context.id. After an ASID rollover, the generation of the HOUSEKEEPING domain can be flushed independently, and only the TLB of HOUSEKEEPING domain CPUs will be flushed, so the processes of ISOLATION domain will not be affected. In addition, the ASID of the ISOLATION domain is stored in the isolated_asid bitmap. When the asid_map is refreshed, the isolated_asid must be copied to the asid_map to ensure that the ASID of the ISOLATION domain is not allocated by other processes. The following figure shows the example: HOUSEKEEPING (genid: G1) ISOLATION (genid: G2) task1(G1,1) task2(G2,2) task3(G2,3) cpu0 cpu1 cpu3 cpu4 cpu5 ------------------------- ----------------------- \ / | \ / isolated_asid: [2,3] \ / asid_map: [1,2,3,4,...,65536] The task1 is running on the HOUSEKEEPING domain, it allocate ASID 1 from shared asid_map, so the context id of task1 is (G1,1). The task2 and task3 are running on the ISOLATION domain, they allocate ASID 2,3 from shared asid_map, and store ASID 2,3 to isolated_asid. the context id of task2 is (G2,2), and the context id of task3 is (G2,3). After a rollover, the generation of HOUSEKEEPING doamin is flushed, for example, it becomes to G3, then the context id of task1 is changed to (G3,1). In this time, the generation of ISOLATION domain is not affected. In some scenarios, a process has multiple threads, and different threads run in different domains, or processes migrate between different domains. But the process has only one context ID, there is a problem that how to select generation in this case. The way we're thinking is, as long as the process has run to ISOLATION doamin, select generation of ISOLATION doamin. For example: HOUSEKEEPING (genid: G1) ISOLATION (genid: G2) task1(G1,1) ====> task1(G2,1) task2(G2,2) <==== task2(G2,2) cpu0 cpu1 cpu3 cpu4 cpu5 ------------------------- ----------------------- When task1 is migrated from HOUSEKEEPING domain to ISOLATION domain, the generation G1 must be changed to G2, and save the ASID 1 to isolated_asid bitmap. But when task2 is migrated from ISOLATION domain to HOUSEKEEPING domain, it still use generation G2. In this way, we solve the problem that which generation should be selected in the scenario of process migration. As mentioned before, the generation of different domains is different. we divide the generation into two parts, the lowest bit is used as the Flag bit to indicate the HOUSEKEEPING and ISOLATION domain, and the rest bits are used as the Upper-generation. After a rollover, only the Upper-generation is flushed, the Flag part does not change in the entire life. This ensures that the genrentaion of different domains is different. asid_generation |---------------------------|-|--------| Upper-generation Flag Finally, it is important to select which domain generation and TLBs are flushed after a rollover. By default, only the HOUSEKEEPING domain is selected. When the number of ASIDs in the ISOLATION domain exceeds the max threshold, the ISOLATION domain is selected too. By default, the ASID isolation feature is disabled, and a cmdline parameter is provided to control whether the ASID isolation feature is enabled. Signed-off-by: Yunfeng Ye --- arch/arm64/mm/context.c | 203 ++++++++++++++++++++++++++++++++++++---- 1 file changed, 183 insertions(+), 20 deletions(-) diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index e402997aa1c2..0ea3e7485ae7 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include @@ -24,10 +25,20 @@ struct asid_bitmap { unsigned long max; }; +enum { + ASID_HOUSEKEEPING = 0, + ASID_ISOLATION = 1, + ASID_TYPE_MAX, +}; + +struct asid_domain { + atomic64_t asid_generation; +}; + static u32 asid_bits; static DEFINE_RAW_SPINLOCK(cpu_asid_lock); -static atomic64_t asid_generation; +static struct asid_domain asid_domain[ASID_TYPE_MAX]; static unsigned long *asid_map; static DEFINE_PER_CPU(atomic64_t, active_asids); @@ -36,11 +47,16 @@ static cpumask_t tlb_flush_pending; static const struct cpumask *asid_housekeeping_mask; static struct asid_bitmap pinned_asid; +static struct asid_bitmap isolated_asid; + +static int asid_isolation_cmdline; +static DEFINE_STATIC_KEY_FALSE(asid_isolation_enable); #define ASID_MASK (~GENMASK(asid_bits - 1, 0)) -#define ASID_FIRST_VERSION (1UL << asid_bits) +#define NUM_USER_ASIDS (1UL << asid_bits) -#define NUM_USER_ASIDS ASID_FIRST_VERSION +#define ASID_ISOLATION_FLAG (NUM_USER_ASIDS) +#define ASID_FIRST_VERSION (NUM_USER_ASIDS << 1) #define ctxid2asid(asid) ((asid) & ~ASID_MASK) #define asid2ctxid(asid, genid) ((asid) | (genid)) @@ -94,6 +110,61 @@ static void set_kpti_asid_bits(unsigned long *map) memset(map, 0xaa, len); } +static inline bool is_isolated_asid(u64 asid) +{ + /* + * Note that asid 0 is not the isolated asid. The judgment + * is correct in this situation since the ASID_ISOLATION_FLAG + * bit is defined as 1 to indicate ISOLATION domain. + */ + return asid & ASID_ISOLATION_FLAG; +} + +static inline bool on_isolated_cpu(int cpu) +{ + return !cpumask_test_cpu(cpu, asid_housekeeping_mask); +} + +static inline int asid_domain_type(u64 asid, unsigned int cpu) +{ + if (on_isolated_cpu(cpu) || is_isolated_asid(asid)) + return ASID_ISOLATION; + + return ASID_HOUSEKEEPING; +} + +static inline int asid_flush_type(void) +{ + if (isolated_asid.nr > isolated_asid.max) + return ASID_ISOLATION; + else + return ASID_HOUSEKEEPING; +} + +static void asid_try_to_isolate(u64 asid) +{ + if (!static_branch_unlikely(&asid_isolation_enable)) + return; + + if (!is_isolated_asid(asid)) + return; + if (!__test_and_set_bit(ctxid2asid(asid), isolated_asid.map)) + isolated_asid.nr++; +} + +static void update_reserved_asid_bits(void) +{ + if (!static_branch_unlikely(&asid_isolation_enable)) + return; + + if (asid_flush_type() == ASID_HOUSEKEEPING) { + bitmap_or(asid_map, asid_map, isolated_asid.map, NUM_USER_ASIDS); + } else { + bitmap_zero(isolated_asid.map, NUM_USER_ASIDS); + isolated_asid.nr = 0; + } +} + static void set_reserved_asid_bits(void) { if (pinned_asid.map) @@ -102,23 +173,51 @@ static void set_reserved_asid_bits(void) set_kpti_asid_bits(asid_map); else bitmap_clear(asid_map, 0, NUM_USER_ASIDS); + + update_reserved_asid_bits(); } static void asid_generation_init(void) { - atomic64_set(&asid_generation, ASID_FIRST_VERSION); + struct asid_domain *ad; + + ad = &asid_domain[ASID_HOUSEKEEPING]; + atomic64_set(&ad->asid_generation, ASID_FIRST_VERSION); + + ad = &asid_domain[ASID_ISOLATION]; + atomic64_set(&ad->asid_generation, ASID_ISOLATION_FLAG); } static void flush_generation(void) { + struct asid_domain *ad = &asid_domain[ASID_HOUSEKEEPING]; + /* We're out of ASIDs, so increment the global generation count */ atomic64_add_return_relaxed(ASID_FIRST_VERSION, - &asid_generation); + &ad->asid_generation); + + if (asid_flush_type() == ASID_ISOLATION) { + ad = &asid_domain[ASID_ISOLATION]; + atomic64_add_return_relaxed(ASID_FIRST_VERSION, + &ad->asid_generation); + } } -static inline u64 asid_read_generation(void) +static inline u64 asid_read_generation(int type) { - return atomic64_read(&asid_generation); + struct asid_domain *ad = &asid_domain[type]; + + return atomic64_read(&ad->asid_generation); +} + +static inline u64 asid_curr_generation(u64 asid) +{ + int type = ASID_HOUSEKEEPING; + + if (static_branch_unlikely(&asid_isolation_enable)) + type = asid_domain_type(asid, smp_processor_id()); + + return asid_read_generation(type); } static inline bool asid_match(u64 asid, u64 genid) @@ -128,12 +227,28 @@ static inline bool asid_match(u64 asid, u64 genid) static inline bool asid_gen_match(u64 asid) { - return asid_match(asid, asid_read_generation()); + return asid_match(asid, asid_curr_generation(asid)); +} + +static bool asid_is_migrated(u64 asid, u64 newasid) +{ + if (!static_branch_unlikely(&asid_isolation_enable)) + return false; + + if (!is_isolated_asid(asid) && is_isolated_asid(newasid)) { + u64 generation = asid_read_generation(ASID_HOUSEKEEPING); + + return asid_match(asid, generation); + } + return false; } static const struct cpumask *flush_cpumask(void) { - return asid_housekeeping_mask; + if (asid_flush_type() == ASID_HOUSEKEEPING) + return asid_housekeeping_mask; + + return cpu_possible_mask; } static void flush_context(void) @@ -159,6 +274,7 @@ static void flush_context(void) if (asid == 0) asid = per_cpu(reserved_asids, i); __set_bit(ctxid2asid(asid), asid_map); + asid_try_to_isolate(asid); per_cpu(reserved_asids, i) = asid; } @@ -193,21 +309,23 @@ static bool check_update_reserved_asid(u64 asid, u64 newasid) return hit; } -static u64 new_context(struct mm_struct *mm) +static u64 new_context(struct mm_struct *mm, unsigned int cpu) { static u32 cur_idx = 1; u64 asid = atomic64_read(&mm->context.id); - u64 generation = asid_read_generation(); + int domain = asid_domain_type(asid, cpu); + u64 generation = asid_read_generation(domain); + u64 newasid; if (asid != 0) { - u64 newasid = asid2ctxid(ctxid2asid(asid), generation); + newasid = asid2ctxid(ctxid2asid(asid), generation); /* * If our current ASID was active during a rollover, we * can continue to use it and this was just a false alarm. */ if (check_update_reserved_asid(asid, newasid)) - return newasid; + goto out; /* * If it is pinned, we can keep using it. Note that reserved @@ -215,14 +333,21 @@ static u64 new_context(struct mm_struct *mm) * update the generation into the reserved_asids. */ if (refcount_read(&mm->context.pinned)) - return newasid; + goto out; /* * We had a valid ASID in a previous life, so try to re-use * it if possible. */ if (!__test_and_set_bit(ctxid2asid(asid), asid_map)) - return newasid; + goto out; + + /* + * We still have a valid ASID now, but the ASID is migrated from + * normal to isolated domain, we should re-use it. + */ + if (asid_is_migrated(asid, newasid)) + goto out; } /* @@ -241,11 +366,14 @@ static u64 new_context(struct mm_struct *mm) /* We have more ASIDs than CPUs, so this will always succeed */ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1); - generation = asid_read_generation(); + generation = asid_read_generation(domain); set_asid: __set_bit(asid, asid_map); cur_idx = asid; - return asid2ctxid(asid, generation); + newasid = asid2ctxid(asid, generation); +out: + asid_try_to_isolate(newasid); + return newasid; } void check_and_switch_context(struct mm_struct *mm) @@ -282,12 +410,12 @@ void check_and_switch_context(struct mm_struct *mm) raw_spin_lock_irqsave(&cpu_asid_lock, flags); /* Check that our ASID belongs to the current generation. */ asid = atomic64_read(&mm->context.id); + cpu = smp_processor_id(); if (!asid_gen_match(asid)) { - asid = new_context(mm); + asid = new_context(mm, cpu); atomic64_set(&mm->context.id, asid); } - cpu = smp_processor_id(); if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) local_flush_tlb_all(); @@ -327,11 +455,12 @@ unsigned long arm64_mm_context_get(struct mm_struct *mm) } if (!asid_gen_match(asid)) { + unsigned int cpu = smp_processor_id(); /* * We went through one or more rollover since that ASID was * used. Ensure that it is still valid, or generate a new one. */ - asid = new_context(mm); + asid = new_context(mm, cpu); atomic64_set(&mm->context.id, asid); } @@ -430,10 +559,36 @@ static int asids_update_limit(void) * are pinned, there still is at least one empty slot in the ASID map. */ pinned_asid.max = num_available_asids - num_possible_cpus() - 2; + + /* + * Generally, the user does not care about the number of asids, so set + * to half of the total number as the default setting of the maximum + * threshold of the isolated asid. + */ + if (isolated_asid.map) + isolated_asid.max = num_available_asids / 2; + return 0; } arch_initcall(asids_update_limit); +static void asid_isolation_init(void) +{ + if (asid_isolation_cmdline == 0) + return; + + if (!housekeeping_enabled(HK_TYPE_DOMAIN)) + return; + + isolated_asid.map = bitmap_zalloc(NUM_USER_ASIDS, GFP_KERNEL); + if (!isolated_asid.map) + return; + + asid_housekeeping_mask = housekeeping_cpumask(HK_TYPE_DOMAIN); + static_branch_enable(&asid_isolation_enable); + pr_info("ASID Isolation enable\n"); +} + static int asids_init(void) { asid_bits = get_cpu_asid_bits(); @@ -448,6 +603,7 @@ static int asids_init(void) pinned_asid.nr = 0; asid_housekeeping_mask = cpu_possible_mask; + asid_isolation_init(); /* * We cannot call set_reserved_asid_bits() here because CPU @@ -459,3 +615,10 @@ static int asids_init(void) return 0; } early_initcall(asids_init); + +static int __init asid_isolation_setup(char *str) +{ + asid_isolation_cmdline = 1; + return 1; +} +__setup("asid_isolation", asid_isolation_setup); -- 2.27.0