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Subject[PATCH 35/40] KVM: direct mmio pfn check
Date
From: Ben-Ami Yassour <benami@il.ibm.com>

Userspace may specify memory slots that are backed by mmio pages rather than
normal RAM. In some cases it is not enough to identify these mmio pages
by pfn_valid(). This patch adds checking the PageReserved as well.

Signed-off-by: Ben-Ami Yassour <benami@il.ibm.com>
Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
virt/kvm/kvm_main.c | 22 +++++++++++++++-------
1 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7dd9b0b..5eb96c7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -76,6 +76,14 @@ static inline int valid_vcpu(int n)
return likely(n >= 0 && n < KVM_MAX_VCPUS);
}

+static inline int is_mmio_pfn(pfn_t pfn)
+{
+ if (pfn_valid(pfn))
+ return PageReserved(pfn_to_page(pfn));
+
+ return true;
+}
+
/*
* Switches to specified vcpu, until a matching vcpu_put()
*/
@@ -740,7 +748,7 @@ pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
}

pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
- BUG_ON(pfn_valid(pfn));
+ BUG_ON(!is_mmio_pfn(pfn));
} else
pfn = page_to_pfn(page[0]);

@@ -754,10 +762,10 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
pfn_t pfn;

pfn = gfn_to_pfn(kvm, gfn);
- if (pfn_valid(pfn))
+ if (!is_mmio_pfn(pfn))
return pfn_to_page(pfn);

- WARN_ON(!pfn_valid(pfn));
+ WARN_ON(is_mmio_pfn(pfn));

get_page(bad_page);
return bad_page;
@@ -773,7 +781,7 @@ EXPORT_SYMBOL_GPL(kvm_release_page_clean);

void kvm_release_pfn_clean(pfn_t pfn)
{
- if (pfn_valid(pfn))
+ if (!is_mmio_pfn(pfn))
put_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_release_pfn_clean);
@@ -799,7 +807,7 @@ EXPORT_SYMBOL_GPL(kvm_set_page_dirty);

void kvm_set_pfn_dirty(pfn_t pfn)
{
- if (pfn_valid(pfn)) {
+ if (!is_mmio_pfn(pfn)) {
struct page *page = pfn_to_page(pfn);
if (!PageReserved(page))
SetPageDirty(page);
@@ -809,14 +817,14 @@ EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);

void kvm_set_pfn_accessed(pfn_t pfn)
{
- if (pfn_valid(pfn))
+ if (!is_mmio_pfn(pfn))
mark_page_accessed(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);

void kvm_get_pfn(pfn_t pfn)
{
- if (pfn_valid(pfn))
+ if (!is_mmio_pfn(pfn))
get_page(pfn_to_page(pfn));
}
EXPORT_SYMBOL_GPL(kvm_get_pfn);
--
1.6.0.1


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