kvm: mmu: Fix overflow on kvm mmu page limit calculation

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KVM bases its memory usage limits on the total number of guest pages
across all memslots. However, those limits, and the calculations to
produce them, use 32 bit unsigned integers. This can result in overflow
if a VM has more guest pages that can be represented by a u32. As a
result of this overflow, KVM can use a low limit on the number of MMU
pages it will allocate. This makes KVM unable to map all of guest memory
at once, prompting spurious faults.

Tested: Ran all kvm-unit-tests on an Intel Haswell machine. This patch
	introduced no new failures.

Signed-off-by: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

...

This commit is contained in:

Ben Gardon 2019-04-08 11:07:30 -07:00 • committed by Paolo Bonzini

parent 2b27924bb1

commit bc8a3d8925

4 changed files with 15 additions and 16 deletions

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12

arch/x86/include/asm/kvm_host.h

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13

arch/x86/kvm/mmu.c

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2

arch/x86/kvm/mmu.h

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4

arch/x86/kvm/x86.c

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