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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 63219CA5FCB for ; Wed, 30 Sep 2026 15:35:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:Cc:To:From: Subject:Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=22jRFGKxaXFtlNaZ+C1HtHMLzFRhPhrTjV8Sjs2+m0c=; b=gcGvep+Yc1fz7xiaswE25sDXJ/ s72OqZS1l1hbe89sRNjXW384oAeWi0ft5hxNpGcacFcz5KrzzFrD0R0Tw15cPe3gWcGmMJL7dH8+L w6gFFxZj99kpZK76SPjjcSfyldezv4sEjRDHXQqIcoVbOI1Oz+w/4gzua0YZVDe9HzQjuZN/iEtf8 72dGvos3Pg8HMoGORk2mNXoGPKghcySXeQq6GGe/DXyd1cpPgXpSH5+2y1zWpLEcDhX30XhGaDkgG XponPtYItXaOyl+lCXjgT3hE+9JPKPFjE3JVztLoG4bkiQXlmgArqQyB45Y6BaYI0yUaRZYZIbKL3 l25Vl+TA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBwLJ-00000006XKX-2vIr; Wed, 30 Sep 2026 15:35:37 +0000 Received: from mail-wm1-f71.google.com ([209.85.128.71]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBwLC-00000006XHQ-1aFx for linux-arm-kernel@lists.infradead.org; Wed, 30 Sep 2026 15:35:32 +0000 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-495689bfcc8so47040605e9.1 for ; Wed, 30 Sep 2026 08:35:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790782527; x=1791387327; darn=lists.infradead.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=22jRFGKxaXFtlNaZ+C1HtHMLzFRhPhrTjV8Sjs2+m0c=; b=vKXY4E0KD3Y6BVd1xx9Va6e2slGiHPLPJFd7OnZwulY3GYJ85VNyGO4cfDy3L+f44p Rr7FbhfQeha0x9oZjqzVxr5fkgLG55E4PqyOMU50E/dBQqMUbeC4YE0ikWhppE347G5o or5ySOSfcE6v/EOOL19znTrtQP5l55PRZKAhCjsd38olfNtcKDKoYmauD+L74B4h21IM OoxqvR1k3kSbGY2uzVVercHm/Nt7t3zzcSb16s293+Syn5/BMSKcSgFl+VKe8bH8MHWa gwDtoXYncaMAOgXFpj5ygy1yu/xCS3fDKtXS7Fe39KKGQunwCs2TM6493c5b5hcEKhrX kieA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790782527; x=1791387327; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=22jRFGKxaXFtlNaZ+C1HtHMLzFRhPhrTjV8Sjs2+m0c=; b=PwrjSEbKUZ523RlNwZwAWoEUPzLexUHdkuxf54o+KB9FSVsfAhpwhgJsWerjhZcMoc nkCaMOA7oi2003b84UFa28PCostfTkGRvUrsnlcLP0s2Mog8vgA+jm7Qtn5/Z6jcDVXZ 0DmT+P71i0yxNIQrsNz0qCQyN72t7wIjVBDswY9V8A54ffc/s8Rjq/4Bbbc8rXwTdttx wPCMDpsWx/Bw5wcHWyCRInJq9acJE6sooC42K1Sb19KgRVbBH/Dc4HXDGTf2POfZm3CD JgM+txWtOGsajwJ3g15/mP8Bx2mhXqe4ZBC1Jy1jS16uDIQPqdlpSoJ0zuGPh8M7g8Dc 2/aA== X-Forwarded-Encrypted: i=1; AKwUvBwg4B05RIo/PeHUd60yXyP2b4eNwHXUCpzIi6Zq1YtXExHkBHgaXzkptMrUTQapDpnPqd2q6ZLZ/6zoa8fHpqFe@lists.infradead.org X-Gm-Message-State: AFuF++nux9TNceAD2BeogC6QpHNOC7BuDIWoMuN6VfVgBQepBm4LwqtI 4nth9ogf2r5aF470C40D6S+QqOt32KCdYb3bJdItLBhBdd8PNo95Grmxma5F8kXz5DljWn1H8Xt 1/a89ONxWE5KfrFVnyyS6Qg== X-Received: from wmox21.prod.google.com ([2002:a05:600c:1795:b0:4a0:1203:95d0]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:3b21:b0:49e:817a:ca7 with SMTP id 5b1f17b1804b1-4a01afe1ec3mr31096795e9.8.1790782527166; Wed, 30 Sep 2026 08:35:27 -0700 (PDT) Date: Wed, 30 Sep 2026 16:35:05 +0100 In-Reply-To: <20260930153505.2144559-1-vdonnefort@google.com> Mime-Version: 1.0 References: <20260930153505.2144559-1-vdonnefort@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260930153505.2144559-5-vdonnefort@google.com> Subject: [PATCH v3 4/4] KVM: arm64: Add hyp_printk event to nVHE/pKVM hyp From: Vincent Donnefort To: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, kernel-team@android.com, fuad.tabba@linux.dev, Vincent Donnefort , Fuad Tabba Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260930_083530_491738_4A49C39E X-CRM114-Status: GOOD ( 26.40 ) 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 Create an event to allow developers to log pretty much anything into the hypervisor tracing buffer with trace_hyp_printk(), just like the kernel tracing has the function trace_printk(). trace_hyp_printk("foobar"); trace_hyp_printk("foo=%d", foo); trace_hyp_printk("foo=%d bar=0x%016llx", foo, bar); To ensure writing into the tracing buffer is fast, store the string format into a kernel-accessible ELF section. The hypervisor only has to write into the event the string ID, which is the delta between the hyp_string_fmt and the start of the ELF section. The string format is parsed by the kernel. It is therefore not possible to dereference hypervisor pointers and the format specifier %s is not supported. Also the %p specifiers will fail to find the hypervisor function. To not waste tracing buffer data, use a dynamic size. Each argument is 8 bytes and the in-kernel printing function can simply know how many of them there are by looking at the event length. Signed-off-by: Vincent Donnefort Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba --- arch/arm64/include/asm/kvm_hypevents.h | 14 ++++ arch/arm64/include/asm/kvm_hyptrace.h | 8 +++ arch/arm64/kernel/image-vars.h | 1 + arch/arm64/kernel/vmlinux.lds.S | 4 ++ .../kvm/hyp/include/nvhe/define_events.h | 2 - arch/arm64/kvm/hyp/include/nvhe/trace.h | 65 +++++++++++++++++++ arch/arm64/kvm/hyp/nvhe/events.c | 6 ++ arch/arm64/kvm/hyp_trace.c | 61 +++++++++++++++++ 8 files changed, 159 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/kvm_hypevents.h b/arch/arm64/include/asm/kvm_hypevents.h index 5f6e6789d121..3396deb1a1f8 100644 --- a/arch/arm64/include/asm/kvm_hypevents.h +++ b/arch/arm64/include/asm/kvm_hypevents.h @@ -58,4 +58,18 @@ HYP_EVENT(selftest, ), RE_PRINTK("id=%llu", __entry->id) ); + +/* + * trace_hyp_printk() has too many specificities to be declared with HYP_EVENT(). + * However, we can use a REMOTE_EVENT macro to automatically do the declaration + * for the kernel side. + */ +REMOTE_EVENT_CUSTOM_PRINTK(hyp_printk, + 0, /* id will be overwritten during hyp event init */ + RE_STRUCT( + re_field(u16, fmt_id) + re_field(u64, args[]) + ), + __hyp_trace_printk(evt, seq) +); #endif diff --git a/arch/arm64/include/asm/kvm_hyptrace.h b/arch/arm64/include/asm/kvm_hyptrace.h index de133b735f72..46097105fdd8 100644 --- a/arch/arm64/include/asm/kvm_hyptrace.h +++ b/arch/arm64/include/asm/kvm_hyptrace.h @@ -23,4 +23,12 @@ extern struct remote_event __hyp_events_end[]; extern struct hyp_event_id __hyp_event_ids_start[]; extern struct hyp_event_id __hyp_event_ids_end[]; +#define HYP_STRING_FMT_MAX_SIZE 128 + +struct hyp_string_fmt { + const char fmt[HYP_STRING_FMT_MAX_SIZE]; +}; + +extern struct hyp_string_fmt __hyp_string_fmts_start[]; +extern struct hyp_string_fmt __hyp_string_fmts_end[]; #endif diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h index 14beb7b9d304..ef9875a95f95 100644 --- a/arch/arm64/kernel/image-vars.h +++ b/arch/arm64/kernel/image-vars.h @@ -143,6 +143,7 @@ KVM_NVHE_ALIAS(__hyp_rodata_end); #ifdef CONFIG_NVHE_EL2_TRACING KVM_NVHE_ALIAS(__hyp_event_ids_start); KVM_NVHE_ALIAS(__hyp_event_ids_end); +KVM_NVHE_ALIAS(__hyp_string_fmts_start); #endif /* pKVM static key */ diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index af1d72020976..7f9b6c7dfe70 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -324,6 +324,10 @@ SECTIONS __hyp_events_start = .; *(SORT(_hyp_events.*)) __hyp_events_end = .; + + __hyp_string_fmts_start = .; + *(_hyp_string_fmts) + __hyp_string_fmts_end = .; } #endif /* diff --git a/arch/arm64/kvm/hyp/include/nvhe/define_events.h b/arch/arm64/kvm/hyp/include/nvhe/define_events.h index 776d4c6cb702..370e8c2d39fe 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/define_events.h +++ b/arch/arm64/kvm/hyp/include/nvhe/define_events.h @@ -10,5 +10,3 @@ #define HYP_EVENT_MULTI_READ #include #undef HYP_EVENT_MULTI_READ - -#undef HYP_EVENT diff --git a/arch/arm64/kvm/hyp/include/nvhe/trace.h b/arch/arm64/kvm/hyp/include/nvhe/trace.h index 8813ff250f8e..3d0b5c634bb3 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/trace.h +++ b/arch/arm64/kvm/hyp/include/nvhe/trace.h @@ -46,6 +46,69 @@ static inline pid_t __tracing_get_vcpu_pid(struct kvm_cpu_context *host_ctxt) void *tracing_reserve_entry(unsigned long length); void tracing_commit_entry(void); +/* + * The trace_hyp_printk boilerplate is too fiddly to be declared with + * HYP_EVENT(): + * + * The string format is stored into a kernel-accessible ELF section. The + * hypervisor only writes the format ID. + * + * The function has a variadic prototype. We have no easy way to know each + * argument width so they must all cast to u64. + */ +#define REMOTE_EVENT_CUSTOM_PRINTK(...) + +#define __TO_U64_0() +#define __TO_U64_1(x) , (u64)(x) +#define __TO_U64_2(x, ...) , (u64)(x) __TO_U64_1(__VA_ARGS__) +#define __TO_U64_3(x, ...) , (u64)(x) __TO_U64_2(__VA_ARGS__) +#define __TO_U64_4(x, ...) , (u64)(x) __TO_U64_3(__VA_ARGS__) +#define __TO_U64_5(x, ...) , (u64)(x) __TO_U64_4(__VA_ARGS__) +#define __TO_U64_6(x, ...) , (u64)(x) __TO_U64_5(__VA_ARGS__) +#define __TO_U64_7(x, ...) , (u64)(x) __TO_U64_6(__VA_ARGS__) +#define __TO_U64_8(x, ...) , (u64)(x) __TO_U64_7(__VA_ARGS__) + +#define __TO_U64_X(N, ...) CONCATENATE(__TO_U64_, N)(__VA_ARGS__) +#define __TO_U64(...) __TO_U64_X(COUNT_ARGS(__VA_ARGS__), ##__VA_ARGS__) + +REMOTE_EVENT_FORMAT(hyp_printk, HE_STRUCT(he_field(u16, fmt_id) he_field(u64, args[]))); +extern struct hyp_event_id hyp_event_id_hyp_printk; + +static __always_inline void __trace_hyp_printk(struct hyp_string_fmt *fmt, int nr_args, ...) +{ + struct remote_event_format_hyp_printk *entry; + va_list va; + int i; + + if (!atomic_read(&hyp_event_id_hyp_printk.enabled)) + return; + + entry = tracing_reserve_entry(struct_size(entry, args, nr_args)); + if (!entry) + return; + + entry->hdr.id = hyp_event_id_hyp_printk.id; + entry->fmt_id = fmt - __hyp_string_fmts_start; + + va_start(va, nr_args); + for (i = 0; i < nr_args; i++) + entry->args[i] = va_arg(va, u64); + va_end(va); + + tracing_commit_entry(); +} + + +#define trace_hyp_printk(__fmt, __args...) \ +do { \ + static struct hyp_string_fmt __used __section("_hyp_string_fmts") fmt = { \ + .fmt = __fmt \ + }; \ + BUILD_BUG_ON(sizeof(__fmt) > HYP_STRING_FMT_MAX_SIZE); \ + /* __TO_U64 prepends a comma if there are arguments */ \ + __trace_hyp_printk(&fmt, COUNT_ARGS(__args) __TO_U64(__args)); \ +} while (0) + int __tracing_load(unsigned long desc_va, size_t desc_size); void __tracing_unload(void); int __tracing_enable(bool enable); @@ -58,6 +121,8 @@ static inline void *tracing_reserve_entry(unsigned long length) { return NULL; } static inline void tracing_commit_entry(void) { } #define HYP_EVENT(__name, __proto, __struct, __assign, __printk) \ static inline void trace_##__name(__proto) {} +#define REMOTE_EVENT_CUSTOM_PRINTK(...) +#define trace_hyp_printk(fmt, args...) do { } while (0) static inline int __tracing_load(unsigned long desc_va, size_t desc_size) { return -ENODEV; } static inline void __tracing_unload(void) { } diff --git a/arch/arm64/kvm/hyp/nvhe/events.c b/arch/arm64/kvm/hyp/nvhe/events.c index add9383aadb5..12223d2e3618 100644 --- a/arch/arm64/kvm/hyp/nvhe/events.c +++ b/arch/arm64/kvm/hyp/nvhe/events.c @@ -9,6 +9,12 @@ #include +/* + * The hyp_printk event is not declared with HYP_EVENT in kvm_hypevents.h, + * so we manually add the boilerplate here. + */ +HYP_EVENT(hyp_printk, 0, 0, 0, 0); + int __tracing_enable_event(unsigned short id, bool enable) { struct hyp_event_id *event_id = &__hyp_event_ids_start[id]; diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c index 8faaec899f92..9d4378bcad74 100644 --- a/arch/arm64/kvm/hyp_trace.c +++ b/arch/arm64/kvm/hyp_trace.c @@ -402,6 +402,9 @@ static struct trace_remote_callbacks trace_remote_callbacks = { static const char *__hyp_enter_exit_reason_str(u8 reason); +struct remote_event_format_hyp_printk; +static void __hyp_trace_printk(struct remote_event_format_hyp_printk *entry, struct trace_seq *seq); + #include "define_hypevents.h" static const char *__hyp_enter_exit_reason_str(u8 reason) @@ -421,6 +424,61 @@ static const char *__hyp_enter_exit_reason_str(u8 reason) return strs[min(reason, HYP_REASON_UNKNOWN)]; } +static void __hyp_trace_printk(struct remote_event_format_hyp_printk *entry, struct trace_seq *seq) +{ + const char *fmt = (const char *)(&__hyp_string_fmts_start[entry->fmt_id]); + struct ring_buffer_event *evt = (void *)entry - RB_EVNT_HDR_SIZE; + int nr_args; + + trace_seq_putc(seq, ' '); + + if ((void *)fmt >= (void *)__hyp_string_fmts_end) { + trace_seq_printf(seq, "Unknown hyp_string_fmt ID %d\n", entry->fmt_id); + return; + } + + nr_args = (ring_buffer_event_length(evt) - + offsetof(struct remote_event_format_hyp_printk, args)) / sizeof(entry->args[0]); + switch (nr_args) { + case 0: + trace_seq_printf(seq, fmt); + break; + case 1: + trace_seq_printf(seq, fmt, entry->args[0]); + break; + case 2: + trace_seq_printf(seq, fmt, entry->args[0], entry->args[1]); + break; + case 3: + trace_seq_printf(seq, fmt, entry->args[0], entry->args[1], entry->args[2]); + break; + case 4: + trace_seq_printf(seq, fmt, entry->args[0], entry->args[1], entry->args[2], + entry->args[3]); + break; + case 5: + trace_seq_printf(seq, fmt, entry->args[0], entry->args[1], entry->args[2], + entry->args[3], entry->args[4]); + break; + case 6: + trace_seq_printf(seq, fmt, entry->args[0], entry->args[1], entry->args[2], + entry->args[3], entry->args[4], entry->args[5]); + break; + case 7: + trace_seq_printf(seq, fmt, entry->args[0], entry->args[1], entry->args[2], + entry->args[3], entry->args[4], entry->args[5], entry->args[6]); + break; + default: + trace_seq_printf(seq, fmt, entry->args[0], entry->args[1], + entry->args[2], entry->args[3], entry->args[4], entry->args[5], + entry->args[6], entry->args[7]); + break; + } + + if (seq->buffer[trace_seq_used(seq) - 1] != '\n') + trace_seq_putc(seq, '\n'); +} + static void __init hyp_trace_init_events(void) { struct hyp_event_id *hyp_event_id = __hyp_event_ids_start; @@ -430,6 +488,9 @@ static void __init hyp_trace_init_events(void) /* Events on both sides hypervisor are sorted */ for (; event < __hyp_events_end; event++, hyp_event_id++, id++) event->id = hyp_event_id->id = id; + + WARN(__hyp_string_fmts_end - __hyp_string_fmts_start > U16_MAX + 1, + "Too many trace_hyp_printk() callsites\n"); } int __init kvm_hyp_trace_init(void) -- 2.56.0.rc1.315.gc6ed9934b7-goog