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author | Sean Christopherson <sean.j.christopherson@intel.com> | 2019-11-11 14:12:27 -0800 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-11-12 10:17:42 +0100 |
commit | a78986aae9b2988f8493f9f65a587ee433e83bc3 (patch) | |
tree | a630d421bde6adbf63834c840e3276096ecae4b1 /include | |
parent | 29881b6ec6e453ff8df37ad8f44e17bf0d4e1e12 (diff) | |
download | linux-a78986aae9b2988f8493f9f65a587ee433e83bc3.tar.gz |
KVM: MMU: Do not treat ZONE_DEVICE pages as being reserved
Explicitly exempt ZONE_DEVICE pages from kvm_is_reserved_pfn() and instead manually handle ZONE_DEVICE on a case-by-case basis. For things like page refcounts, KVM needs to treat ZONE_DEVICE pages like normal pages, e.g. put pages grabbed via gup(). But for flows such as setting A/D bits or shifting refcounts for transparent huge pages, KVM needs to to avoid processing ZONE_DEVICE pages as the flows in question lack the underlying machinery for proper handling of ZONE_DEVICE pages. This fixes a hang reported by Adam Borowski[*] in dev_pagemap_cleanup() when running a KVM guest backed with /dev/dax memory, as KVM straight up doesn't put any references to ZONE_DEVICE pages acquired by gup(). Note, Dan Williams proposed an alternative solution of doing put_page() on ZONE_DEVICE pages immediately after gup() in order to simplify the auditing needed to ensure is_zone_device_page() is called if and only if the backing device is pinned (via gup()). But that approach would break kvm_vcpu_{un}map() as KVM requires the page to be pinned from map() 'til unmap() when accessing guest memory, unlike KVM's secondary MMU, which coordinates with mmu_notifier invalidations to avoid creating stale page references, i.e. doesn't rely on pages being pinned. [*] http://lkml.kernel.org/r/20190919115547.GA17963@angband.pl Reported-by: Adam Borowski <kilobyte@angband.pl> Analyzed-by: David Hildenbrand <david@redhat.com> Acked-by: Dan Williams <dan.j.williams@intel.com> Cc: stable@vger.kernel.org Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/kvm_host.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 719fc3e15ea4..290dbe353a47 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -966,6 +966,7 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu); void kvm_vcpu_kick(struct kvm_vcpu *vcpu); bool kvm_is_reserved_pfn(kvm_pfn_t pfn); +bool kvm_is_zone_device_pfn(kvm_pfn_t pfn); struct kvm_irq_ack_notifier { struct hlist_node link; |