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Mon, 26 Jan 2026 02:44:48 -0800 (PST) Date: Mon, 26 Jan 2026 10:44:13 +0000 In-Reply-To: <20260126104419.1649811-1-vdonnefort@google.com> Mime-Version: 1.0 References: <20260126104419.1649811-1-vdonnefort@google.com> X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog Message-ID: <20260126104419.1649811-25-vdonnefort@google.com> Subject: [PATCH v10 24/30] KVM: arm64: Add trace remote for the nVHE/pKVM hyp From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, jstultz@google.com, qperret@google.com, will@kernel.org, aneesh.kumar@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260126_024450_494255_4E09EFC5 X-CRM114-Status: GOOD ( 19.01 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org In both protected and nVHE mode, the hypervisor is capable of writing events into tracefs compatible ring-buffers. Create a trace remote so the kernel can read those buffers. This currently doesn't provide any event support which will come later. Signed-off-by: Vincent Donnefort diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index c7f50492f2cf..aad0228f24db 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -76,6 +76,7 @@ if NVHE_EL2_DEBUG config NVHE_EL2_TRACING bool depends on TRACING + select TRACE_REMOTE default y config PKVM_DISABLE_STAGE2_ON_PANIC diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile index 3ebc0570345c..59612d2f277c 100644 --- a/arch/arm64/kvm/Makefile +++ b/arch/arm64/kvm/Makefile @@ -30,6 +30,8 @@ kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o kvm-$(CONFIG_PTDUMP_STAGE2_DEBUGFS) += ptdump.o +kvm-$(CONFIG_NVHE_EL2_TRACING) += hyp_trace.o + always-y := hyp_constants.h hyp-constants.s define rule_gen_hyp_constants diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index be1fd6c5f74c..f7f222ecaf88 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -24,6 +24,7 @@ #define CREATE_TRACE_POINTS #include "trace_arm.h" +#include "hyp_trace.h" #include #include @@ -2361,6 +2362,10 @@ static int __init init_subsystems(void) kvm_register_perf_callbacks(NULL); + err = kvm_hyp_trace_init(); + if (err) + kvm_err("Failed to initialize Hyp tracing\n"); + out: if (err) hyp_cpu_pm_exit(); diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c new file mode 100644 index 000000000000..2866effe28ec --- /dev/null +++ b/arch/arm64/kvm/hyp_trace.c @@ -0,0 +1,219 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2025 Google LLC + * Author: Vincent Donnefort + */ + +#include +#include + +#include +#include +#include + +#include "hyp_trace.h" + +/* Access to this struct within the trace_remote_callbacks are protected by the trace_remote lock */ +static struct hyp_trace_buffer { + struct hyp_trace_desc *desc; + size_t desc_size; +} trace_buffer; + +static int __map_hyp(void *start, size_t size) +{ + if (is_protected_kvm_enabled()) + return 0; + + return create_hyp_mappings(start, start + size, PAGE_HYP); +} + +static int __share_page(unsigned long va) +{ + return kvm_share_hyp((void *)va, (void *)va + 1); +} + +static void __unshare_page(unsigned long va) +{ + kvm_unshare_hyp((void *)va, (void *)va + 1); +} + +static int hyp_trace_buffer_alloc_bpages_backing(struct hyp_trace_buffer *trace_buffer, size_t size) +{ + int nr_bpages = (PAGE_ALIGN(size) / PAGE_SIZE) + 1; + size_t backing_size; + void *start; + + backing_size = PAGE_ALIGN(sizeof(struct simple_buffer_page) * nr_bpages * + num_possible_cpus()); + + start = alloc_pages_exact(backing_size, GFP_KERNEL_ACCOUNT); + if (!start) + return -ENOMEM; + + trace_buffer->desc->bpages_backing_start = (unsigned long)start; + trace_buffer->desc->bpages_backing_size = backing_size; + + return __map_hyp(start, backing_size); +} + +static void hyp_trace_buffer_free_bpages_backing(struct hyp_trace_buffer *trace_buffer) +{ + free_pages_exact((void *)trace_buffer->desc->bpages_backing_start, + trace_buffer->desc->bpages_backing_size); +} + +static void hyp_trace_buffer_unshare_hyp(struct hyp_trace_buffer *trace_buffer, int last_cpu) +{ + struct ring_buffer_desc *rb_desc; + int cpu, p; + + for_each_ring_buffer_desc(rb_desc, cpu, &trace_buffer->desc->trace_buffer_desc) { + if (cpu > last_cpu) + break; + + __share_page(rb_desc->meta_va); + for (p = 0; p < rb_desc->nr_page_va; p++) + __unshare_page(rb_desc->page_va[p]); + } +} + +static int hyp_trace_buffer_share_hyp(struct hyp_trace_buffer *trace_buffer) +{ + struct ring_buffer_desc *rb_desc; + int cpu, p, ret = 0; + + for_each_ring_buffer_desc(rb_desc, cpu, &trace_buffer->desc->trace_buffer_desc) { + ret = __share_page(rb_desc->meta_va); + if (ret) + break; + + for (p = 0; p < rb_desc->nr_page_va; p++) { + ret = __share_page(rb_desc->page_va[p]); + if (ret) + break; + } + + if (ret) { + for (p--; p >= 0; p--) + __unshare_page(rb_desc->page_va[p]); + break; + } + } + + if (ret) + hyp_trace_buffer_unshare_hyp(trace_buffer, cpu--); + + return ret; +} + +static struct trace_buffer_desc *hyp_trace_load(unsigned long size, void *priv) +{ + struct hyp_trace_buffer *trace_buffer = priv; + struct hyp_trace_desc *desc; + size_t desc_size; + int ret; + + if (WARN_ON(trace_buffer->desc)) + return ERR_PTR(-EINVAL); + + desc_size = trace_buffer_desc_size(size, num_possible_cpus()); + if (desc_size == SIZE_MAX) + return ERR_PTR(-E2BIG); + + desc_size = PAGE_ALIGN(desc_size); + desc = (struct hyp_trace_desc *)alloc_pages_exact(desc_size, GFP_KERNEL); + if (!desc) + return ERR_PTR(-ENOMEM); + + ret = __map_hyp(desc, desc_size); + if (ret) + goto err_free_desc; + + trace_buffer->desc = desc; + + ret = hyp_trace_buffer_alloc_bpages_backing(trace_buffer, size); + if (ret) + goto err_free_desc; + + ret = trace_remote_alloc_buffer(&desc->trace_buffer_desc, desc_size, size, + cpu_possible_mask); + if (ret) + goto err_free_backing; + + ret = hyp_trace_buffer_share_hyp(trace_buffer); + if (ret) + goto err_free_buffer; + + ret = kvm_call_hyp_nvhe(__tracing_load, (unsigned long)desc, desc_size); + if (ret) + goto err_unload_pages; + + return &desc->trace_buffer_desc; + +err_unload_pages: + hyp_trace_buffer_unshare_hyp(trace_buffer, INT_MAX); + +err_free_buffer: + trace_remote_free_buffer(&desc->trace_buffer_desc); + +err_free_backing: + hyp_trace_buffer_free_bpages_backing(trace_buffer); + +err_free_desc: + free_pages_exact(desc, desc_size); + trace_buffer->desc = NULL; + + return ERR_PTR(ret); +} + +static void hyp_trace_unload(struct trace_buffer_desc *desc, void *priv) +{ + struct hyp_trace_buffer *trace_buffer = priv; + + if (WARN_ON(desc != &trace_buffer->desc->trace_buffer_desc)) + return; + + kvm_call_hyp_nvhe(__tracing_unload); + hyp_trace_buffer_unshare_hyp(trace_buffer, INT_MAX); + trace_remote_free_buffer(desc); + hyp_trace_buffer_free_bpages_backing(trace_buffer); + free_pages_exact(trace_buffer->desc, trace_buffer->desc_size); + trace_buffer->desc = NULL; +} + +static int hyp_trace_enable_tracing(bool enable, void *priv) +{ + return kvm_call_hyp_nvhe(__tracing_enable, enable); +} + +static int hyp_trace_swap_reader_page(unsigned int cpu, void *priv) +{ + return kvm_call_hyp_nvhe(__tracing_swap_reader, cpu); +} + +static int hyp_trace_reset(unsigned int cpu, void *priv) +{ + return 0; +} + +static int hyp_trace_enable_event(unsigned short id, bool enable, void *priv) +{ + return 0; +} + +static struct trace_remote_callbacks trace_remote_callbacks = { + .load_trace_buffer = hyp_trace_load, + .unload_trace_buffer = hyp_trace_unload, + .enable_tracing = hyp_trace_enable_tracing, + .swap_reader_page = hyp_trace_swap_reader_page, + .reset = hyp_trace_reset, + .enable_event = hyp_trace_enable_event, +}; + +int __init kvm_hyp_trace_init(void) +{ + if (is_kernel_in_hyp_mode()) + return 0; + + return trace_remote_register("hypervisor", &trace_remote_callbacks, &trace_buffer, NULL, 0); +} diff --git a/arch/arm64/kvm/hyp_trace.h b/arch/arm64/kvm/hyp_trace.h new file mode 100644 index 000000000000..c991b1ec65f1 --- /dev/null +++ b/arch/arm64/kvm/hyp_trace.h @@ -0,0 +1,11 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef __ARM64_KVM_HYP_TRACE_H__ +#define __ARM64_KVM_HYP_TRACE_H__ + +#ifdef CONFIG_NVHE_EL2_TRACING +int kvm_hyp_trace_init(void); +#else +static inline int kvm_hyp_trace_init(void) { return 0; } +#endif +#endif -- 2.52.0.457.g6b5491de43-goog