diff options
| author | Li zeming <zeming@nfschina.com> | 2023-09-06 02:20:06 +0800 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-10-18 14:34:28 -0700 |
| commit | 1de9992f9de0a92b6e11133aba0e2be833c11084 (patch) | |
| tree | 535552bfb3636e440a654188008c6f66e9c03ca6 /arch/x86/kvm/mmu/mmu.c | |
| parent | c9f65a3f2d92e0de336177d0151dabaf3ed004e5 (diff) | |
KVM: x86/mmu: Remove unnecessary ‘NULL’ values from sptep
Don't initialize "spte" and "sptep" in fast_page_fault() as they are both
guaranteed (for all intents and purposes) to be written at the start of
every loop iteration. Add a sanity check that "sptep" is non-NULL after
walking the shadow page tables, as encountering a NULL root would result
in "spte" not being written, i.e. would lead to uninitialized data or the
previous value being consumed.
Signed-off-by: Li zeming <zeming@nfschina.com>
Link: https://lore.kernel.org/r/20230905182006.2964-1-zeming@nfschina.com
[sean: rewrite changelog with --verbose]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm/mmu/mmu.c')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 5d3dc7119e57..b0f01d605617 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3425,8 +3425,8 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_mmu_page *sp; int ret = RET_PF_INVALID; - u64 spte = 0ull; - u64 *sptep = NULL; + u64 spte; + u64 *sptep; uint retry_count = 0; if (!page_fault_can_be_fast(fault)) @@ -3442,6 +3442,14 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) else sptep = fast_pf_get_last_sptep(vcpu, fault->addr, &spte); + /* + * It's entirely possible for the mapping to have been zapped + * by a different task, but the root page should always be + * available as the vCPU holds a reference to its root(s). + */ + if (WARN_ON_ONCE(!sptep)) + spte = REMOVED_SPTE; + if (!is_shadow_present_pte(spte)) break; |