port-amd64/59369: panic: kernel diagnostic assertion "!samepage" failed

[campbell+netbsd%mumble.net@localhost]

>Number:         59369
>Category:       port-amd64
>Synopsis:       panic: kernel diagnostic assertion "!samepage" failed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Apr 28 01:55:00 +0000 2025
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The PmapBSD Samepagination
>Environment:
NetBSD 10.99.14 (GENERIC) #0: Sun Apr 27 22:58:52 UTC 2025
	root%babylon4.netbsd.org@localhost:/tmp/build/2025.04.27.22.03.22-i386/obj/sys/arch/i386/compile/GENERIC
>Description:
[   7.0664833] boot device: wd0
[   7.0664833] root on dk0 dumps on dk1
[   7.0718669] root file system type: ffs
[   7.0718669] kern.module.path=/stand/i386/10.99.14/modules
[  41.9832245] panic: kernel diagnostic assertion "!samepage" failed: file "/tmp/build/2025.04.27.22.03.22-i386/src/sys/arch/x86/x86/pmap.c", line 5214 
[  41.9832245] cpu0: Begin traceback...
[  41.9832245] vpanic(c138c9a4,c91ac7e8,c91ac85c,c04d4856,c138c9a4,c1317c5b,c13418ed,c13cadd8,145e,0) at netbsd:vpanic+0x176
[  41.9832245] kern_assert(c138c9a4,c1317c5b,c13418ed,c13cadd8,145e,0,c170eca0,0,1d61315,1d66c67) at netbsd:kern_assert+0x23
[  41.9832245] pmap_enter_ma(c1f10040,b6000,1d66000,1d66000,7,22,0,22,c91ac934,c1f37040) at netbsd:pmap_enter_ma+0x1113
[  41.9832245] pmap_enter_default(c1f10040,b6000,1d66000,7,22,7,b6000,c1f10040,c91ac950,0) at netbsd:pmap_enter_default+0x43
[  41.9832245] uvm_fault_upper_enter(c1f38fe8,c1a11570,c1f38fe8,1,0,c91ac908,c91ac90c,c0d7a7cd,c1c2ac40,c16b9140) at netbsd:uvm_fault_upper_enter+0xb1
[  41.9947326] uvm_fault_internal(c1f0f0c0,b6000,2,0,0,c166b700,c91aca4c,c04cdc47,c1e37268,c1f0f0c0) at netbsd:uvm_fault_internal+0xf6c
[  41.9947326] trap() at netbsd:trap+0x6e1
[  41.9947326] --- trap (number 6) ---
[  41.9947326] copyout(c898e000,160,c91acc30,c91acb80,c91acb78,100,0,7000,0,2) at netbsd:copyout+0x32
[  41.9947326] ubc_uiomove(c1e28e00,c91acc30,160,0,109,c91acbe8,10,0,0,c1e28e00) at netbsd:ubc_uiomove+0xef
[  41.9947326] ffs_read(c91acbe8,201,c12fc9a0,c1e28e00,c91acc30,10,c1c37040,0,c91acc30,c91acc58) at netbsd:ffs_read+0x137
[  41.9947326] VOP_READ(c1e28e00,c91acc30,10,c1c37040,c0d308f0,c1f0f0c0,c91acc48,b6000,160,c91acc28) at netbsd:VOP_READ+0x44
[  42.0047425] vn_rdwr(0,c1e28e00,b6000,160,7000,0,0,10,c1c37040,0) at netbsd:vn_rdwr+0xd1
[  42.0047425] vmcmd_readvn(c1e21d00,c1d8d9b0,c91acd28,1,c91accfc,c0d7553c,c91ace5c,c91accfc,c91acd40,0) at netbsd:vmcmd_readvn+0x6b
[  42.0047425] execve_runproc(0,bfbfefe8,0,c0d69780,c91acd28,c1f3a000,c1f3a800,ffffffff,c1f3b000,404) at netbsd:execve_runproc+0x34e
[  42.0047425] execve1(c1e21d00,1,bfbfeff5,ffffffff,bfbfefe8,0,c0d69780,c91acf9c,c0d4de97,c1e21d00) at netbsd:execve1+0x61
[  42.0047425] sys_execve(c1e21d00,c91aceec,c91acee4,0,ffffffff,ffffffff,0,b0313,c1378002,c1e21d00) at netbsd:sys_execve+0x40
[  42.0134222] start_init(c1e21d00,1981000,198d000,0,c01005a8,0,0,0,0,0) at netbsd:start_init+0x26e
[  42.0134222] cpu0: End traceback...
[  42.0134222] fatal breakpoint trap in supervisor mode
[  42.0134222] trap type 1 code 0 eip 0xc0128094 cs 0x8 eflags 0x202 cr2 0xb6000 ilevel 0 esp 0xc91ac7cc
[  42.0134222] curlwp 0xc1e21d00 pid 1 lid 1 lowest kstack 0xc91aa2c0
Stopped in pid 1.1 (init) at    netbsd:breakpoint+0x4:  popl    %ebp
db{0}> 

Source: https://releng.netbsd.org/b5reports/i386/2025/2025.04.27.22.03.22/test.log
>How-To-Repeat:
Not a clue!
>Fix:
Yes, please!