arch/x86/kvm/mmu/paging_tmpl.h:106:24: sparse: sparse: cast truncates bits from constant value (ffffffffff000 becomes fffff000)

From: kernel test robot
Date: Mon Sep 19 2022 - 11:32:23 EST


Hi Sean,

FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 521a547ced6477c54b4b0cc206000406c221b4d6
commit: 70e41c31bc7776b262cd9f524df3dfc2b5869a0a KVM: x86/mmu: Use common logic for computing the 32/64-bit base PA mask
date: 3 months ago
config: x86_64-randconfig-s022-20220919 (https://download.01.org/0day-ci/archive/20220919/202209192330.x51kM4LB-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-5) 11.3.0
reproduce:
# apt-get install sparse
# sparse version: v0.6.4-39-gce1a6720-dirty
# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=70e41c31bc7776b262cd9f524df3dfc2b5869a0a
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout 70e41c31bc7776b262cd9f524df3dfc2b5869a0a
# save the config file
mkdir build_dir && cp config build_dir/.config
make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash arch/x86/kvm/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

sparse warnings: (new ones prefixed by >>)
arch/x86/kvm/mmu/mmu.c:610:9: sparse: sparse: context imbalance in 'walk_shadow_page_lockless_begin' - different lock contexts for basic block
arch/x86/kvm/mmu/mmu.c: note: in included file (through include/linux/rbtree.h, include/linux/mm_types.h, arch/x86/kvm/irq.h):
include/linux/rcupdate.h:726:9: sparse: sparse: context imbalance in 'walk_shadow_page_lockless_end' - unexpected unlock
arch/x86/kvm/mmu/mmu.c:2550:9: sparse: sparse: context imbalance in 'mmu_try_to_unsync_pages' - different lock contexts for basic block
arch/x86/kvm/mmu/mmu.c: note: in included file:
>> arch/x86/kvm/mmu/paging_tmpl.h:106:24: sparse: sparse: cast truncates bits from constant value (ffffffffff000 becomes fffff000)
arch/x86/kvm/mmu/paging_tmpl.h:426:24: sparse: sparse: cast truncates bits from constant value (ffffffffff000 becomes fffff000)
arch/x86/kvm/mmu/mmu.c:4618:57: sparse: sparse: cast truncates bits from constant value (ffffff33 becomes 33)
arch/x86/kvm/mmu/mmu.c:4620:56: sparse: sparse: cast truncates bits from constant value (ffffff0f becomes f)
arch/x86/kvm/mmu/mmu.c:4622:57: sparse: sparse: cast truncates bits from constant value (ffffff55 becomes 55)

vim +106 arch/x86/kvm/mmu/paging_tmpl.h

b3fcdb04a98035 arch/x86/kvm/mmu/paging_tmpl.h Sean Christopherson 2022-06-14 103
e04da980c35d75 arch/x86/kvm/paging_tmpl.h Joerg Roedel 2009-07-27 104 static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl)
5fb07ddb183eb4 drivers/kvm/paging_tmpl.h Avi Kivity 2007-11-21 105 {
e04da980c35d75 arch/x86/kvm/paging_tmpl.h Joerg Roedel 2009-07-27 @106 return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT;
5fb07ddb183eb4 drivers/kvm/paging_tmpl.h Avi Kivity 2007-11-21 107 }
5fb07ddb183eb4 drivers/kvm/paging_tmpl.h Avi Kivity 2007-11-21 108

:::::: The code at line 106 was first introduced by commit
:::::: e04da980c35d75fa050ba4009ad99025432d8d7d KVM: MMU: make page walker aware of mapping levels

:::::: TO: Joerg Roedel <joerg.roedel@xxxxxxx>
:::::: CC: Avi Kivity <avi@xxxxxxxxxx>

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