arch/mips/kvm/mmu.c:701:29: warning: variable 'old_pte' set but not used
From: kernel test robot
Date: Fri Oct 06 2023 - 17:24:40 EST
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: af95dc6fdc25e616051d0234aad638e15c02ec8f
commit: 0f78355c450835053fed85828c9d6526594c0921 KVM: MIPS: Enable KVM support for Loongson-3
date: 3 years, 4 months ago
config: mips-loongson3_defconfig (https://download.01.org/0day-ci/archive/20231007/202310070530.aARZCSfh-lkp@xxxxxxxxx/config)
compiler: mips64el-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231007/202310070530.aARZCSfh-lkp@xxxxxxxxx/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310070530.aARZCSfh-lkp@xxxxxxxxx/
All warnings (new ones prefixed by >>):
In file included from include/linux/gfp.h:6,
from include/linux/xarray.h:14,
from include/linux/radix-tree.h:18,
from include/linux/fs.h:15,
from include/linux/highmem.h:5,
from arch/mips/kvm/mmu.c:12:
include/linux/mmzone.h: In function '__nr_to_section':
include/linux/mmzone.h:1201:13: warning: the comparison will always evaluate as 'true' for the address of 'mem_section' will never be NULL [-Waddress]
1201 | if (!mem_section[SECTION_NR_TO_ROOT(nr)])
| ^
include/linux/mmzone.h:1187:27: note: 'mem_section' declared here
1187 | extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
| ^~~~~~~~~~~
arch/mips/kvm/mmu.c: In function 'kvm_mips_map_page':
>> arch/mips/kvm/mmu.c:701:29: warning: variable 'old_pte' set but not used [-Wunused-but-set-variable]
701 | pte_t *ptep, entry, old_pte;
| ^~~~~~~
--
In file included from include/linux/topology.h:33,
from include/linux/irq.h:19,
from include/asm-generic/hardirq.h:13,
from arch/mips/include/asm/hardirq.h:16,
from include/linux/hardirq.h:10,
from include/linux/kvm_host.h:7,
from arch/mips/kvm/loongson_ipi.c:11:
include/linux/mmzone.h: In function '__nr_to_section':
include/linux/mmzone.h:1201:13: warning: the comparison will always evaluate as 'true' for the address of 'mem_section' will never be NULL [-Waddress]
1201 | if (!mem_section[SECTION_NR_TO_ROOT(nr)])
| ^
include/linux/mmzone.h:1187:27: note: 'mem_section' declared here
1187 | extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
| ^~~~~~~~~~~
arch/mips/kvm/loongson_ipi.c: At top level:
>> arch/mips/kvm/loongson_ipi.c:190:6: warning: no previous prototype for 'kvm_init_loongson_ipi' [-Wmissing-prototypes]
190 | void kvm_init_loongson_ipi(struct kvm *kvm)
| ^~~~~~~~~~~~~~~~~~~~~
--
>> arch/mips/kvm/emulate.c:274: warning: Function parameter or member 'out' not described in 'kvm_get_badinstr'
>> arch/mips/kvm/emulate.c:295: warning: Function parameter or member 'out' not described in 'kvm_get_badinstrp'
>> arch/mips/kvm/emulate.c:328: warning: Function parameter or member 'vcpu' not described in 'kvm_mips_ktime_to_count'
>> arch/mips/kvm/emulate.c:328: warning: Function parameter or member 'now' not described in 'kvm_mips_ktime_to_count'
arch/mips/kvm/emulate.c:2376: warning: Function parameter or member 'vcpu' not described in 'kvm_mips_guest_exception_base'
vim +/old_pte +701 arch/mips/kvm/mmu.c
b5f1dd1ba4042bda James Hogan 2016-12-06 667
06c158c96ed8909a James Hogan 2015-05-01 668 /**
06c158c96ed8909a James Hogan 2015-05-01 669 * kvm_mips_map_page() - Map a guest physical page.
06c158c96ed8909a James Hogan 2015-05-01 670 * @vcpu: VCPU pointer.
06c158c96ed8909a James Hogan 2015-05-01 671 * @gpa: Guest physical address of fault.
577ed7f71e9c37a4 James Hogan 2015-05-01 672 * @write_fault: Whether the fault was due to a write.
06c158c96ed8909a James Hogan 2015-05-01 673 * @out_entry: New PTE for @gpa (written on success unless NULL).
06c158c96ed8909a James Hogan 2015-05-01 674 * @out_buddy: New PTE for @gpa's buddy (written on success unless
06c158c96ed8909a James Hogan 2015-05-01 675 * NULL).
06c158c96ed8909a James Hogan 2015-05-01 676 *
06c158c96ed8909a James Hogan 2015-05-01 677 * Handle GPA faults by creating a new GPA mapping (or updating an existing
06c158c96ed8909a James Hogan 2015-05-01 678 * one).
06c158c96ed8909a James Hogan 2015-05-01 679 *
411740f5422a960c James Hogan 2016-12-13 680 * This takes care of marking pages young or dirty (idle/dirty page tracking),
411740f5422a960c James Hogan 2016-12-13 681 * asking KVM for the corresponding PFN, and creating a mapping in the GPA page
411740f5422a960c James Hogan 2016-12-13 682 * tables. Derived mappings (GVA page tables and TLBs) must be handled by the
411740f5422a960c James Hogan 2016-12-13 683 * caller.
06c158c96ed8909a James Hogan 2015-05-01 684 *
06c158c96ed8909a James Hogan 2015-05-01 685 * Returns: 0 on success, in which case the caller may use the @out_entry
06c158c96ed8909a James Hogan 2015-05-01 686 * and @out_buddy PTEs to update derived mappings and resume guest
06c158c96ed8909a James Hogan 2015-05-01 687 * execution.
06c158c96ed8909a James Hogan 2015-05-01 688 * -EFAULT if there is no memory region at @gpa or a write was
06c158c96ed8909a James Hogan 2015-05-01 689 * attempted to a read-only memory region. This is usually handled
06c158c96ed8909a James Hogan 2015-05-01 690 * as an MMIO access.
06c158c96ed8909a James Hogan 2015-05-01 691 */
06c158c96ed8909a James Hogan 2015-05-01 692 static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
577ed7f71e9c37a4 James Hogan 2015-05-01 693 bool write_fault,
06c158c96ed8909a James Hogan 2015-05-01 694 pte_t *out_entry, pte_t *out_buddy)
06c158c96ed8909a James Hogan 2015-05-01 695 {
06c158c96ed8909a James Hogan 2015-05-01 696 struct kvm *kvm = vcpu->kvm;
06c158c96ed8909a James Hogan 2015-05-01 697 struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
06c158c96ed8909a James Hogan 2015-05-01 698 gfn_t gfn = gpa >> PAGE_SHIFT;
06c158c96ed8909a James Hogan 2015-05-01 699 int srcu_idx, err;
06c158c96ed8909a James Hogan 2015-05-01 700 kvm_pfn_t pfn;
06c158c96ed8909a James Hogan 2015-05-01 @701 pte_t *ptep, entry, old_pte;
411740f5422a960c James Hogan 2016-12-13 702 bool writeable;
06c158c96ed8909a James Hogan 2015-05-01 703 unsigned long prot_bits;
411740f5422a960c James Hogan 2016-12-13 704 unsigned long mmu_seq;
403015b323a29747 James Hogan 2016-06-09 705
411740f5422a960c James Hogan 2016-12-13 706 /* Try the fast path to handle old / clean pages */
403015b323a29747 James Hogan 2016-06-09 707 srcu_idx = srcu_read_lock(&kvm->srcu);
b5f1dd1ba4042bda James Hogan 2016-12-06 708 err = _kvm_mips_map_page_fast(vcpu, gpa, write_fault, out_entry,
b5f1dd1ba4042bda James Hogan 2016-12-06 709 out_buddy);
b5f1dd1ba4042bda James Hogan 2016-12-06 710 if (!err)
b5f1dd1ba4042bda James Hogan 2016-12-06 711 goto out;
06c158c96ed8909a James Hogan 2015-05-01 712
06c158c96ed8909a James Hogan 2015-05-01 713 /* We need a minimum of cached pages ready for page table creation */
06c158c96ed8909a James Hogan 2015-05-01 714 err = mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES,
06c158c96ed8909a James Hogan 2015-05-01 715 KVM_NR_MEM_OBJS);
06c158c96ed8909a James Hogan 2015-05-01 716 if (err)
06c158c96ed8909a James Hogan 2015-05-01 717 goto out;
06c158c96ed8909a James Hogan 2015-05-01 718
411740f5422a960c James Hogan 2016-12-13 719 retry:
411740f5422a960c James Hogan 2016-12-13 720 /*
411740f5422a960c James Hogan 2016-12-13 721 * Used to check for invalidations in progress, of the pfn that is
411740f5422a960c James Hogan 2016-12-13 722 * returned by pfn_to_pfn_prot below.
411740f5422a960c James Hogan 2016-12-13 723 */
411740f5422a960c James Hogan 2016-12-13 724 mmu_seq = kvm->mmu_notifier_seq;
411740f5422a960c James Hogan 2016-12-13 725 /*
411740f5422a960c James Hogan 2016-12-13 726 * Ensure the read of mmu_notifier_seq isn't reordered with PTE reads in
411740f5422a960c James Hogan 2016-12-13 727 * gfn_to_pfn_prot() (which calls get_user_pages()), so that we don't
411740f5422a960c James Hogan 2016-12-13 728 * risk the page we get a reference to getting unmapped before we have a
411740f5422a960c James Hogan 2016-12-13 729 * chance to grab the mmu_lock without mmu_notifier_retry() noticing.
411740f5422a960c James Hogan 2016-12-13 730 *
411740f5422a960c James Hogan 2016-12-13 731 * This smp_rmb() pairs with the effective smp_wmb() of the combination
411740f5422a960c James Hogan 2016-12-13 732 * of the pte_unmap_unlock() after the PTE is zapped, and the
411740f5422a960c James Hogan 2016-12-13 733 * spin_lock() in kvm_mmu_notifier_invalidate_<page|range_end>() before
411740f5422a960c James Hogan 2016-12-13 734 * mmu_notifier_seq is incremented.
411740f5422a960c James Hogan 2016-12-13 735 */
411740f5422a960c James Hogan 2016-12-13 736 smp_rmb();
403015b323a29747 James Hogan 2016-06-09 737
411740f5422a960c James Hogan 2016-12-13 738 /* Slow path - ask KVM core whether we can access this GPA */
411740f5422a960c James Hogan 2016-12-13 739 pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writeable);
ba913e4f72fc9cfd James Hogan 2016-08-19 740 if (is_error_noslot_pfn(pfn)) {
403015b323a29747 James Hogan 2016-06-09 741 err = -EFAULT;
403015b323a29747 James Hogan 2016-06-09 742 goto out;
403015b323a29747 James Hogan 2016-06-09 743 }
403015b323a29747 James Hogan 2016-06-09 744
06c158c96ed8909a James Hogan 2015-05-01 745 spin_lock(&kvm->mmu_lock);
411740f5422a960c James Hogan 2016-12-13 746 /* Check if an invalidation has taken place since we got pfn */
411740f5422a960c James Hogan 2016-12-13 747 if (mmu_notifier_retry(kvm, mmu_seq)) {
411740f5422a960c James Hogan 2016-12-13 748 /*
411740f5422a960c James Hogan 2016-12-13 749 * This can happen when mappings are changed asynchronously, but
411740f5422a960c James Hogan 2016-12-13 750 * also synchronously if a COW is triggered by
411740f5422a960c James Hogan 2016-12-13 751 * gfn_to_pfn_prot().
411740f5422a960c James Hogan 2016-12-13 752 */
411740f5422a960c James Hogan 2016-12-13 753 spin_unlock(&kvm->mmu_lock);
411740f5422a960c James Hogan 2016-12-13 754 kvm_release_pfn_clean(pfn);
411740f5422a960c James Hogan 2016-12-13 755 goto retry;
411740f5422a960c James Hogan 2016-12-13 756 }
06c158c96ed8909a James Hogan 2015-05-01 757
b5f1dd1ba4042bda James Hogan 2016-12-06 758 /* Ensure page tables are allocated */
06c158c96ed8909a James Hogan 2015-05-01 759 ptep = kvm_mips_pte_for_gpa(kvm, memcache, gpa);
06c158c96ed8909a James Hogan 2015-05-01 760
b5f1dd1ba4042bda James Hogan 2016-12-06 761 /* Set up the PTE */
411740f5422a960c James Hogan 2016-12-13 762 prot_bits = _PAGE_PRESENT | __READABLE | _page_cachable_default;
411740f5422a960c James Hogan 2016-12-13 763 if (writeable) {
411740f5422a960c James Hogan 2016-12-13 764 prot_bits |= _PAGE_WRITE;
b5f1dd1ba4042bda James Hogan 2016-12-06 765 if (write_fault) {
b5f1dd1ba4042bda James Hogan 2016-12-06 766 prot_bits |= __WRITEABLE;
b5f1dd1ba4042bda James Hogan 2016-12-06 767 mark_page_dirty(kvm, gfn);
411740f5422a960c James Hogan 2016-12-13 768 kvm_set_pfn_dirty(pfn);
411740f5422a960c James Hogan 2016-12-13 769 }
b5f1dd1ba4042bda James Hogan 2016-12-06 770 }
06c158c96ed8909a James Hogan 2015-05-01 771 entry = pfn_pte(pfn, __pgprot(prot_bits));
06c158c96ed8909a James Hogan 2015-05-01 772
b5f1dd1ba4042bda James Hogan 2016-12-06 773 /* Write the PTE */
06c158c96ed8909a James Hogan 2015-05-01 774 old_pte = *ptep;
06c158c96ed8909a James Hogan 2015-05-01 775 set_pte(ptep, entry);
06c158c96ed8909a James Hogan 2015-05-01 776
06c158c96ed8909a James Hogan 2015-05-01 777 err = 0;
06c158c96ed8909a James Hogan 2015-05-01 778 if (out_entry)
06c158c96ed8909a James Hogan 2015-05-01 779 *out_entry = *ptep;
06c158c96ed8909a James Hogan 2015-05-01 780 if (out_buddy)
06c158c96ed8909a James Hogan 2015-05-01 781 *out_buddy = *ptep_buddy(ptep);
06c158c96ed8909a James Hogan 2015-05-01 782
06c158c96ed8909a James Hogan 2015-05-01 783 spin_unlock(&kvm->mmu_lock);
411740f5422a960c James Hogan 2016-12-13 784 kvm_release_pfn_clean(pfn);
411740f5422a960c James Hogan 2016-12-13 785 kvm_set_pfn_accessed(pfn);
403015b323a29747 James Hogan 2016-06-09 786 out:
403015b323a29747 James Hogan 2016-06-09 787 srcu_read_unlock(&kvm->srcu, srcu_idx);
403015b323a29747 James Hogan 2016-06-09 788 return err;
403015b323a29747 James Hogan 2016-06-09 789 }
403015b323a29747 James Hogan 2016-06-09 790
:::::: The code at line 701 was first introduced by commit
:::::: 06c158c96ed8909a1d8696d4f953ca8a9ef55574 KVM: MIPS/MMU: Convert guest physical map to page table
:::::: TO: James Hogan <james.hogan@xxxxxxxxxx>
:::::: CC: James Hogan <james.hogan@xxxxxxxxxx>
--
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