summaryrefslogtreecommitdiff
path: root/include/linux
diff options
context:
space:
mode:
authorSean Christopherson <sean.j.christopherson@intel.com>2019-11-12 01:12:27 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-12-01 11:14:15 +0300
commitfdfce30d9877e61f14692eb70df7f76a42a3726b (patch)
treedb4f9959e6bbc67e14ae79cb9b1d856da48e66ce /include/linux
parent79d404a2aa86efe4f1ade51e054318bd811cce71 (diff)
downloadlinux-fdfce30d9877e61f14692eb70df7f76a42a3726b.tar.xz
KVM: MMU: Do not treat ZONE_DEVICE pages as being reserved
commit a78986aae9b2988f8493f9f65a587ee433e83bc3 upstream. 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> [sean: backport to 4.x; resolve conflict in mmu.c] Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/kvm_host.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index bb4758ffd403..7668c68ddb5b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -890,6 +890,7 @@ 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;