From 8d30b16f75feb556fd6d38b05fae1b23923a8f16 Mon Sep 17 00:00:00 2001
From: Arthur Hanson Rasmusson <arthur@vgpu.io>
Date: Thu, 24 Sep 2026 08:53:00 -0400
Subject: tools/guest-diag: add UVM rm_mem kprobe dump for VA->PA ground truth

The probe dumps {type, CPU VA, GPU VAs, size} on every
uvm_rm_mem_get_cpu_va call (and the first 64 bytes of the object's CPU
mapping with nested fetchargs), which is how the host-side learned map
can be checked against what the guest actually created.
---
 tools/guest-diag/uvm_rmmem_probe.sh | 40 +++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100755 tools/guest-diag/uvm_rmmem_probe.sh

(limited to 'tools')

diff --git a/tools/guest-diag/uvm_rmmem_probe.sh b/tools/guest-diag/uvm_rmmem_probe.sh
new file mode 100755
index 0000000..15ad73f
--- /dev/null
+++ b/tools/guest-diag/uvm_rmmem_probe.sh
@@ -0,0 +1,40 @@
+#!/bin/sh
+# uvm_rmmem_probe.sh - guest-side kprobe that dumps every UVM rm_mem mapping
+# as it is used: {type, CPU VA, GPU0 VA, GPU1 VA, size} for each call to
+# uvm_rm_mem_get_cpu_va. This is the ground truth for VA -> physical
+# translations that the host-side scan has to rediscover (the CPU VA is a
+# direct-map address for sysmem objects that are mapped page by page, and a
+# vmap address for objects mapped through nv_vm_map_pages; only the former can
+# be turned into a physical address by subtracting the direct-map base).
+#
+# The pushbuffer/semaphore-pool content can also be read straight out of the
+# kernel with nested fetchargs, e.g. a0=+0(+48(%di)):x64 reads the first u64
+# of the object's CPU mapping.
+#
+# Run as root in the guest, after nvidia-uvm is loaded and before starting the
+# client (the first calls happen during bring-up):
+#   sudo sh uvm_rmmem_probe.sh
+#   ... start the CUDA workload ...
+#   sudo grep rmcpu /sys/kernel/tracing/trace
+#
+# Note: kprobe writes must be plain "echo ... >> file" redirections. Piping
+# through tee returns EINVAL on this kernel.
+set -e
+T=/sys/kernel/tracing
+
+echo 0 >> $T/events/kprobes/rmcpu/enable 2>/dev/null || true
+echo 0 >> $T/events/kprobes/pb/enable 2>/dev/null || true
+echo > $T/kprobe_events
+printf 'p:rmcpu uvm_rm_mem_get_cpu_va type=+0(%%di):u32 cpu_va=+48(%%di):x64 gpu0=+56(%%di):x64 gpu1=+64(%%di):x64 size=+2120(%%di):x64\n' >> $T/kprobe_events
+printf 'p:pb uvm_rm_mem_get_cpu_va gpu0=+56(%%di):x64 a0=+0(+48(%%di)):x64 a1=+8(+48(%%di)):x64 a2=+16(+48(%%di)):x64 a3=+24(+48(%%di)):x64 a4=+32(+48(%%di)):x64 a5=+40(+48(%%di)):x64 a6=+48(+48(%%di)):x64 a7=+56(+48(%%di)):x64\n' >> $T/kprobe_events
+cat > $T/events/kprobes/rmcpu/filter <<'EOF'
+gpu0 != 0x121000000
+EOF
+cat > $T/events/kprobes/pb/filter <<'EOF'
+gpu0 == 0x120000000
+EOF
+echo > $T/trace
+echo 1 >> $T/events/kprobes/rmcpu/enable
+echo 1 >> $T/events/kprobes/pb/enable
+cat $T/kprobe_events
+echo "enabled; traces in $T/trace"
\ No newline at end of file
-- 
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