There's an ongoing effort to remove VLAs[1] from the kernel to eventually turn on -Wvla. It turns out, the few VLAs in use in Xen produce only a single entry array that is always bounded by GDT_SIZE. Clean up the code to get rid of the VLA and the loop.
[1] https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Laura Abbott <labb...@redhat.com> --- v2: Updated the code to reflect that we know size is always bounded by GDT_SIZE. This gets rid of the array and the loop. I can throw a few more comments in there if someone thinks they need to be updated. --- arch/x86/xen/enlighten_pv.c | 84 ++++++++++++++++----------------------------- 1 file changed, 29 insertions(+), 55 deletions(-) diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index c36d23aa6c35..1254f2fa3a89 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -421,45 +421,32 @@ static void xen_load_gdt(const struct desc_ptr *dtr) { unsigned long va = dtr->address; unsigned int size = dtr->size + 1; - unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE); - unsigned long frames[pages]; - int f; - - /* - * A GDT can be up to 64k in size, which corresponds to 8192 - * 8-byte entries, or 16 4k pages.. - */ + unsigned long pfn, mfn; + int level; + pte_t *ptep; + void *virt; - BUG_ON(size > 65536); + BUG_ON(size > GDT_SIZE); BUG_ON(va & ~PAGE_MASK); - for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) { - int level; - pte_t *ptep; - unsigned long pfn, mfn; - void *virt; - - /* - * The GDT is per-cpu and is in the percpu data area. - * That can be virtually mapped, so we need to do a - * page-walk to get the underlying MFN for the - * hypercall. The page can also be in the kernel's - * linear range, so we need to RO that mapping too. - */ - ptep = lookup_address(va, &level); - BUG_ON(ptep == NULL); - - pfn = pte_pfn(*ptep); - mfn = pfn_to_mfn(pfn); - virt = __va(PFN_PHYS(pfn)); + /* + * The GDT is per-cpu and is in the percpu data area. + * That can be virtually mapped, so we need to do a + * page-walk to get the underlying MFN for the + * hypercall. The page can also be in the kernel's + * linear range, so we need to RO that mapping too. + */ + ptep = lookup_address(va, &level); + BUG_ON(ptep == NULL); - frames[f] = mfn; + pfn = pte_pfn(*ptep); + mfn = pfn_to_mfn(pfn); + virt = __va(PFN_PHYS(pfn)); - make_lowmem_page_readonly((void *)va); - make_lowmem_page_readonly(virt); - } + make_lowmem_page_readonly((void *)va); + make_lowmem_page_readonly(virt); - if (HYPERVISOR_set_gdt(frames, size / sizeof(struct desc_struct))) + if (HYPERVISOR_set_gdt(&mfn, size / sizeof(struct desc_struct))) BUG(); } @@ -470,34 +457,21 @@ static void __init xen_load_gdt_boot(const struct desc_ptr *dtr) { unsigned long va = dtr->address; unsigned int size = dtr->size + 1; - unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE); - unsigned long frames[pages]; - int f; - - /* - * A GDT can be up to 64k in size, which corresponds to 8192 - * 8-byte entries, or 16 4k pages.. - */ + unsigned long pfn, mfn; + pte_t pte; - BUG_ON(size > 65536); + BUG_ON(size > GDT_SIZE); BUG_ON(va & ~PAGE_MASK); - for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) { - pte_t pte; - unsigned long pfn, mfn; + pfn = virt_to_pfn(va); + mfn = pfn_to_mfn(pfn); - pfn = virt_to_pfn(va); - mfn = pfn_to_mfn(pfn); + pte = pfn_pte(pfn, PAGE_KERNEL_RO); - pte = pfn_pte(pfn, PAGE_KERNEL_RO); - - if (HYPERVISOR_update_va_mapping((unsigned long)va, pte, 0)) - BUG(); - - frames[f] = mfn; - } + if (HYPERVISOR_update_va_mapping((unsigned long)va, pte, 0)) + BUG(); - if (HYPERVISOR_set_gdt(frames, size / sizeof(struct desc_struct))) + if (HYPERVISOR_set_gdt(&mfn, size / sizeof(struct desc_struct))) BUG(); } -- 2.14.3 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
