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b=JLTGDx4jkYO6rCsLPTkfwcGiYcDeLR7/nVDsghDGniU+c6haoY7REaiN1wy3sBlq9 S1Nx/SQUNHYJzFYW4DRllsixtoyyp/z5EwPSAfaxytqjmLjM5Dyz9qZOt9GuNlhP9S CEDQmNM5EHH2448doM3f0Cx8X+uz/iUSnP+Ojva/p3O6299cR8zioP7BcoYWpmAUo2 8TrFbVfbFfqiy5367kLCW+wwOTigWd0zQxJceJ5lXZ+N1IwOPma7GgW0fQskrRVRo2 PPso+aj/XoqEE0emE98JGMwkcULoKFxl0uhcw0ahNwqCoY4uoeT7hW5MCZUSasVRxk Uc9tZlxit/BCg== Date: Tue, 18 Nov 2025 15:44:48 -0700 From: Nathan Chancellor To: "Vishal Moola (Oracle)" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Uladzislau Rezki , Christoph Hellwig , Andrew Morton , Christoph Hellwig , kvmarm@lists.linux.dev Subject: Re: [PATCH v3 1/4] mm/vmalloc: warn on invalid vmalloc gfp flags Message-ID: <20251118224448.GA998046@ax162> References: <20251117173530.43293-1-vishal.moola@gmail.com> <20251117173530.43293-2-vishal.moola@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251117173530.43293-2-vishal.moola@gmail.com> X-Stat-Signature: fmh1d33wqr7617pqmitunj9dmeax4mmb X-Rspam-User: X-Rspamd-Queue-Id: 7D405160009 X-Rspamd-Server: rspam10 X-HE-Tag: 1763505896-393543 X-HE-Meta: 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 h26p+PfZ A04tJqW8IV42RUiyFPNqXYoXGRdH4BI5Y3k8do9UtZMBat+FH9KditkEZsCvVOY0ZKcmdCzsmHJgReC+RDBPrtmJO4hCJa194Yn8r7H/jekrOzcArHEBlJM4jFhtWjM61eWx0b0jJwcDr9AXPJ33LBjPZP00AlvUbtYkWJB1kyfs15YsMVakFy79s+77AeAKvPC4b17wTKvNo90WiCwbzdX58/F+okx7KMdlOuhtsH7/TuJqtjw1rsvdP8IA1LQIBOO/23CZy1SOcIcrlBD7dM+KTSPlvg4W1SNp3ulVf/zTzT7jg+y/fxGexYpv9GoOcplco8Hn+oqVsBOhlQGcacspIdpIy9vq9REFIhmbF0TuRkCqi31d+FCPGF9Ew834N1VIeISzR6kstwCr3+NDOqYeA4A== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Vishal, On Mon, Nov 17, 2025 at 09:35:27AM -0800, Vishal Moola (Oracle) wrote: > Vmalloc explicitly supports a list of flags, but we never enforce them. > vmalloc has been trying to handle unsupported flags by clearing and > setting flags wherever necessary. This is messy and makes the code > harder to understand, when we could simply check for a supported input > immediately instead. > > Define a helper mask and function telling callers they have passed in > invalid flags, and clear those unsupported vmalloc flags. > > Suggested-by: Christoph Hellwig > Signed-off-by: Vishal Moola (Oracle) > Reviewed-by: Christoph Hellwig > --- > mm/vmalloc.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 0832f944544c..5dc467c6cab4 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3911,6 +3911,28 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, > return NULL; > } > > +/* > + * See __vmalloc_node_range() for a clear list of supported vmalloc flags. > + * This gfp lists all flags currently passed through vmalloc. Currently, > + * __GFP_ZERO is used by BPF and __GFP_NORETRY is used by percpu. Both drm > + * and BPF also use GFP_USER. Additionally, various users pass > + * GFP_KERNEL_ACCOUNT. > + */ > +#define GFP_VMALLOC_SUPPORTED (GFP_KERNEL | GFP_ATOMIC | GFP_NOWAIT |\ > + __GFP_NOFAIL | __GFP_ZERO | __GFP_NORETRY |\ > + GFP_NOFS | GFP_NOIO | GFP_KERNEL_ACCOUNT |\ > + GFP_USER) > + > +static gfp_t vmalloc_fix_flags(gfp_t flags) > +{ > + gfp_t invalid_mask = flags & ~GFP_VMALLOC_SUPPORTED; > + > + flags &= GFP_VMALLOC_SUPPORTED; > + WARN(1, "Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n", > + invalid_mask, &invalid_mask, flags, &flags); > + return flags; > +} I am seeing this warning trigger when starting a VM on one of my arm64 boxes. [ 6345.145795] ------------[ cut here ]------------ [ 6345.145803] Unexpected gfp: 0x2 (__GFP_HIGHMEM). Fixing up to gfp: 0x400dc0 (GFP_KERNEL_ACCOUNT|__GFP_ZERO). Fix your code! [ 6345.145819] WARNING: mm/vmalloc.c:3940 at vmalloc_fix_flags+0x60/0x90, CPU#32: qemu-system-aar/4325 [ 6345.176990] Modules linked in: ... [ 6345.254421] CPU: 32 UID: 1000 PID: 4325 Comm: qemu-system-aar Not tainted 6.18.0-rc6-next-20251118-00002-g2331e73a4769 #1 PREEMPT(voluntary) [ 6345.267101] Hardware name: To be filled by O.E.M Ampere Altra Developer Platform/Ampere Altra Developer Platform, BIOS TianoCore 2.10.100.02 (SYS: 2.10.20 [ 6345.280907] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 6345.287856] pc : vmalloc_fix_flags+0x60/0x90 [ 6345.292115] lr : vmalloc_fix_flags+0x58/0x90 [ 6345.296374] sp : ffff80008d5b3a10 [ 6345.299676] x29: ffff80008d5b3a20 x28: ffff07ff8a148000 x27: 0000000000000000 [ 6345.306800] x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 [ 6345.313923] x23: 000000000000000b x22: 000000000000ae01 x21: 0000000000000028 [ 6345.321047] x20: ffffc682ea643fbc x19: 0000000000001040 x18: ffff800083465050 [ 6345.328170] x17: 00000000d949c370 x16: 00000000d949c370 x15: 0000000000000004 [ 6345.335294] x14: 0000000000000002 x13: 0000000000000002 x12: 0000000000000000 [ 6345.342417] x11: 0000000000000001 x10: ffffc682ec577744 x9 : bf6a46a6bf3b7900 [ 6345.349541] x8 : bf6a46a6bf3b7900 x7 : 65646f632072756f x6 : 7920786946202e29 [ 6345.356664] x5 : ffff081f6fcdc678 x4 : 0000000000000000 x3 : ffff80008d5b3688 [ 6345.363788] x2 : 0000000000000021 x1 : 0000000000000000 x0 : 000000000000006f [ 6345.370911] Call trace: [ 6345.373346] vmalloc_fix_flags+0x60/0x90 (P) [ 6345.377606] __vmalloc_noprof+0xa0/0xb0 [ 6345.381431] kvm_arch_alloc_vm+0x64/0x70 [ 6345.385344] kvm_dev_ioctl+0x9c/0x58c [ 6345.388997] __arm64_sys_ioctl+0xb0/0x100 [ 6345.392995] invoke_syscall+0x84/0xf4 [ 6345.396648] el0_svc_common.llvm.4390888008543260363+0x90/0xf4 [ 6345.402469] do_el0_svc+0x2c/0x3c [ 6345.405773] el0_svc+0x54/0x2a8 [ 6345.408905] el0t_64_sync_handler+0x88/0x134 [ 6345.413164] el0t_64_sync+0x1b8/0x1bc [ 6345.416815] ---[ end trace 0000000000000000 ]--- where kvm_arch_alloc_vm() from arch/arm64/kvm/arm.c is struct kvm *kvm_arch_alloc_vm(void) { size_t sz = sizeof(struct kvm); if (!has_vhe()) return kzalloc(sz, GFP_KERNEL_ACCOUNT); return __vmalloc(sz, GFP_KERNEL_ACCOUNT | __GFP_HIGHMEM | __GFP_ZERO); } Should __GFP_HIGHMEM be dropped from the call to __vmalloc? It looks like it was added by commit 115bae923ac8 ("KVM: arm64: Add memcg accounting to KVM allocations") back in 5.16. Cheers, Nathan