On Wed, 31 Jan 2024 at 14:56, Thomas Huth <th...@redhat.com> wrote: > There's still a vla left in the ppc kvm code: > > https://gitlab.com/thuth/qemu/-/jobs/6063230079#L2005 > > ../target/ppc/kvm.c: In function ‘kvmppc_save_htab’: > ../target/ppc/kvm.c:2691:5: error: ISO C90 forbids variable length array > ‘buf’ [-Werror=vla] > 2691 | uint8_t buf[bufsize]; > | ^~~~~~~ > ../target/ppc/kvm.c: In function ‘kvmppc_read_hptes’: > ../target/ppc/kvm.c:2773:9: error: ISO C90 forbids variable length array > ‘buf’ [-Werror=vla] > 2773 | char buf[sizeof(*hdr) + m * HASH_PTE_SIZE_64]; > | ^~~~ > cc1: all warnings being treated as errors
Thanks for catching that -- it being in code built only on ppc hosts I missed it. kvm_ppc_save_htab() is called twice, and in both cases the bufsize passed in is MAX_KVM_BUF_SIZE. So we could drop that argument and have the buf[] array always be MAX_KVM_BUF_SIZE. kvmppc_read_hptes() does this: int m = n < HPTES_PER_GROUP ? n : HPTES_PER_GROUP; char buf[sizeof(*hdr) + m * HASH_PTE_SIZE_64]; HPTES_PER_GROUP is 8 and HASH_PTE_SIZE_64 is 16, so we aren't saving many bytes of stack by trying to make the buf smaller based on the value of n. So we could have the buf always be [sizeof(*hdr) + HPTES_PER_GROUP * HASH_PTE_SIZE_64]. thanks -- PMM