<div dir="ltr"><br><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">---------- Forwarded message ---------<br>De: <strong class="gmail_sendername" dir="auto">Sergi Perich</strong> <span dir="auto"><<a href="mailto:info@sergiperich.es">info@sergiperich.es</a>></span><br>Date: sáb, 14 mar 2026 a las 13:24<br>Subject: nvidia-kernel-dkms 550.163.01 DKMS build fails on kernel 6.19 - root cause and fix<br>To: <<a href="mailto:1130057@bugs.debian.org">1130057@bugs.debian.org</a>><br></div><br><br><div dir="ltr"><div>To: <a href="mailto:1130057@bugs.debian.org" target="_blank">1130057@bugs.debian.org</a><br><br>Hello,<br><br>I am providing a detailed root cause analysis for this bug based on<br>direct inspection of the 550.163.01 source on a Debian trixie system.<br><br>== ROOT CAUSE ==<br><br>The problem is in conftest.sh, in the vm_area_struct_has_const_vm_flags<br>detection block (line 6529).<br><br>The conftest detects NV_VM_AREA_STRUCT_HAS_CONST_VM_FLAGS by compiling:<br><br> #include <linux/mm_types.h><br> int conftest_vm_area_struct_has_const_vm_flags(void) {<br> return offsetof(struct vm_area_struct, __vm_flags);<br> }<br><br>In kernel 6.19, __vm_flags was removed from the vm_area_struct union,<br>so this compile test fails and NV_VM_AREA_STRUCT_HAS_CONST_VM_FLAGS<br>is left undefined.<br><br>With that macro undefined, nv-mm.h evaluates nv_vm_flags_set() and<br>nv_vm_flags_clear() as follows:<br><br> static inline void nv_vm_flags_set(struct vm_area_struct *vma,<br> vm_flags_t flags)<br> {<br> #if !NV_CAN_CALL_VMA_START_WRITE<br> nv_vma_start_write(vma);<br> ACCESS_PRIVATE(vma, __vm_flags) |= flags; /* FAILS on 6.19 */<br> #elif defined(NV_VM_AREA_STRUCT_HAS_CONST_VM_FLAGS)<br> vm_flags_set(vma, flags); /* correct for 6.19 */<br> #else<br> vma->vm_flags |= flags;<br> #endif<br> }<br><br>NV_CAN_CALL_VMA_START_WRITE is defined in nv-mm.h based on whether<br>NV_IS_EXPORT_SYMBOL_GPL___vma_start_write is set. On Debian kernels<br>__vma_start_write is GPL-only, so NV_IS_EXPORT_SYMBOL_GPL___vma_start_write<br>is never set, NV_CAN_CALL_VMA_START_WRITE is always 0, and the first<br>branch is always taken — hitting the now-missing __vm_flags field.<br><br>The correct branch for kernel 6.19 is the second one (vm_flags_set),<br>but it is never reached because NV_VM_AREA_STRUCT_HAS_CONST_VM_FLAGS<br>is undefined.<br><br>== FIX ==<br><br>Add a second compile test in the same case block in conftest.sh,<br>immediately after the existing one and before the ;; terminator.<br>The second test checks for vm_flags_set(). If it compiles, it defines<br>NV_VM_AREA_STRUCT_HAS_CONST_VM_FLAGS to 1, overriding the previous<br>#undef. This is safe because append_conftest() writes sequentially<br>to stdout and the C preprocessor uses the last definition.<br><br>--- a/conftest.sh<br>+++ b/conftest.sh<br>@@ -6542,6 +6542,13 @@ vm_area_struct_has_const_vm_flags)<br> }"<br> compile_check_conftest "$CODE" \<br> "NV_VM_AREA_STRUCT_HAS_CONST_VM_FLAGS" "" "types"<br>+ CODE="<br>+ #include <linux/mm_types.h><br>+ #include <linux/mm.h><br>+ void conftest_vm_flags_set_exists(struct vm_area_struct *vma) {<br>+ vm_flags_set(vma, (vm_flags_t)0);<br>+ }"<br>+ compile_check_conftest "$CODE" \<br>+ "NV_VM_AREA_STRUCT_HAS_CONST_VM_FLAGS" "1" "types"<br> ;;<br><br>== AFFECTED ==<br><br>nvidia-kernel-dkms 550.163.01-4 on Linux 6.19.6+deb14-amd64.<br>Linux <= 6.18 unaffected.<br><br>== NOTE ==<br><br>The 550 branch is required for Maxwell (GTX 900) and Pascal (GTX 1000)<br>GPUs which are not supported by the 575+ driver.<br><br>Regards</div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div style="text-align:left"></div></div></div></div>
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