From: Sean Christopherson <sean.j.christopherson@intel.com>
To: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Adam Borowski <kilobyte@angband.pl>,
David Hildenbrand <david@redhat.com>,
Dan Williams <dan.j.williams@intel.com>
Subject: [PATCH 1/2] KVM: MMU: Do not treat ZONE_DEVICE pages as being reserved
Date: Wed, 6 Nov 2019 09:07:26 -0800 [thread overview]
Message-ID: <20191106170727.14457-2-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20191106170727.14457-1-sean.j.christopherson@intel.com>
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 KVM needs special handling
in other flows where ZONE_DEVICE pages lack the underlying machinery,
e.g. when setting accessed/dirty bits and shifting refcounts for
transparent huge 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().
[*] http://lkml.kernel.org/r/20190919115547.GA17963@angband.pl
Reported-by: Adam Borowski <kilobyte@angband.pl>
Debugged-by: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/mmu.c | 8 ++++----
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_main.c | 19 +++++++++++++++----
3 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 24c23c66b226..bf82b1f2e834 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3306,7 +3306,7 @@ static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,
* here.
*/
if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn) &&
- level == PT_PAGE_TABLE_LEVEL &&
+ !kvm_is_zone_device_pfn(pfn) && level == PT_PAGE_TABLE_LEVEL &&
PageTransCompoundMap(pfn_to_page(pfn)) &&
!mmu_gfn_lpage_is_disallowed(vcpu, gfn, PT_DIRECTORY_LEVEL)) {
unsigned long mask;
@@ -5914,9 +5914,9 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
* the guest, and the guest page table is using 4K page size
* mapping if the indirect sp has level = 1.
*/
- if (sp->role.direct &&
- !kvm_is_reserved_pfn(pfn) &&
- PageTransCompoundMap(pfn_to_page(pfn))) {
+ if (sp->role.direct && !kvm_is_reserved_pfn(pfn) &&
+ !kvm_is_zone_device_pfn(pfn) &&
+ PageTransCompoundMap(pfn_to_page(pfn))) {
pte_list_remove(rmap_head, sptep);
if (kvm_available_flush_tlb_with_range())
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a817e446c9aa..4ad1cd7d2d4d 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;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b8534c6b8cf6..0a781b1fb8f0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -151,12 +151,23 @@ __weak int kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
{
+ /*
+ * ZONE_DEVICE pages currently set PG_reserved, but from a refcounting
+ * perspective they are "normal" pages, albeit with slightly different
+ * usage rules.
+ */
if (pfn_valid(pfn))
- return PageReserved(pfn_to_page(pfn));
+ return PageReserved(pfn_to_page(pfn)) &&
+ !is_zone_device_page(pfn_to_page(pfn));
return true;
}
+bool kvm_is_zone_device_pfn(kvm_pfn_t pfn)
+{
+ return pfn_valid(pfn) && is_zone_device_page(pfn_to_page(pfn));
+}
+
/*
* Switches to specified vcpu, until a matching vcpu_put()
*/
@@ -1865,7 +1876,7 @@ EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty);
void kvm_set_pfn_dirty(kvm_pfn_t pfn)
{
- if (!kvm_is_reserved_pfn(pfn)) {
+ if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn)) {
struct page *page = pfn_to_page(pfn);
SetPageDirty(page);
@@ -1875,14 +1886,14 @@ EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);
void kvm_set_pfn_accessed(kvm_pfn_t pfn)
{
- if (!kvm_is_reserved_pfn(pfn))
+ if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
mark_page_accessed(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);
void kvm_get_pfn(kvm_pfn_t pfn)
{
- if (!kvm_is_reserved_pfn(pfn))
+ if (!kvm_is_reserved_pfn(pfn) && !WARN_ON(kvm_is_zone_device_pfn(pfn)))
get_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_get_pfn);
--
2.24.0
next prev parent reply other threads:[~2019-11-06 17:07 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 17:07 [PATCH 0/2] KVM: MMU: Fix a refcount bug with ZONE_DEVICE pages Sean Christopherson
2019-11-06 17:07 ` Sean Christopherson [this message]
2019-11-06 17:14 ` [PATCH 1/2] KVM: MMU: Do not treat ZONE_DEVICE pages as being reserved Paolo Bonzini
2019-11-06 17:46 ` Sean Christopherson
2019-11-06 18:04 ` Dan Williams
2019-11-06 20:26 ` Sean Christopherson
2019-11-06 20:34 ` Dan Williams
2019-11-06 21:09 ` Paolo Bonzini
2019-11-06 21:30 ` Sean Christopherson
2019-11-06 23:20 ` Dan Williams
2019-11-06 23:39 ` Sean Christopherson
2019-11-07 0:01 ` Dan Williams
2019-11-07 5:48 ` Dan Williams
2019-11-07 11:12 ` Paolo Bonzini
2019-11-07 15:36 ` Dan Williams
2019-11-07 15:58 ` Sean Christopherson
2019-11-09 1:43 ` Sean Christopherson
2019-11-09 2:00 ` Dan Williams
2019-11-11 18:27 ` Sean Christopherson
2019-11-11 19:15 ` Paolo Bonzini
2019-11-12 0:51 ` Dan Williams
2019-11-12 10:19 ` Paolo Bonzini
2019-11-12 16:57 ` Sean Christopherson
2019-11-06 17:07 ` [PATCH 2/2] KVM: x86/mmu: Add helper to consolidate huge page promotion Sean Christopherson
2019-11-06 17:22 ` Paolo Bonzini
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