On 2014/11/14 18:11, Paolo Bonzini wrote:
On 14/11/2014 10:31, Tiejun Chen wrote:
In PAE case maxphyaddr may be 52bit as well, we also need to
disable mmio page fault. Here we can check MMIO_SPTE_GEN_HIGH_SHIFT
directly to determine if we should set the present bit, and
bring a little cleanup.
Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 23 +++++++++++++++++++++++
arch/x86/kvm/x86.c | 30 ------------------------------
3 files changed, 24 insertions(+), 30 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index dc932d3..667f2b6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -809,6 +809,7 @@ void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask);
void kvm_mmu_zap_all(struct kvm *kvm);
+void kvm_set_mmio_spte_mask(void);
void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm);
unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm);
void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages);
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ac1c4de..8e4be36 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -295,6 +295,29 @@ static bool check_mmio_spte(struct kvm *kvm, u64 spte)
return likely(kvm_gen == spte_gen);
}
+/*
+ * Set the reserved bits and the present bit of an paging-structure
+ * entry to generate page fault with PFER.RSV = 1.
+ */
+void kvm_set_mmio_spte_mask(void)
+{
+ u64 mask;
+ int maxphyaddr = boot_cpu_data.x86_phys_bits;
+
+ /* Mask the reserved physical address bits. */
+ mask = rsvd_bits(maxphyaddr, MMIO_SPTE_GEN_HIGH_SHIFT - 1);
+
+ /* Magic bits are always reserved for 32bit host. */
+ mask |= 0x3ull << 62;
This should be enough to trigger the page fault on PAE systems.
The problem is specific to non-EPT 64-bit hosts, where the PTEs have no
reserved bits beyond 51:MAXPHYADDR. On EPT we use WX- permissions to
trigger EPT misconfig, on 32-bit systems we have bit 62.
Thanks for your explanation.
+ /* Set the present bit to enable mmio page fault. */
+ if (maxphyaddr < MMIO_SPTE_GEN_HIGH_SHIFT)
+ mask = PT_PRESENT_MASK;
Shouldn't this be "|=" anyway, instead of "="?
Yeah, just miss this. Thanks a lot, I will fix this in next revision.
Thanks
Tiejun
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