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[PATCH 3.13.y-ckt 14/85] KVM: MMU: fix validation of mmio page fault

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3.13.11-ckt28 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xiao Guangrong <guangrong.xiao@linux.intel.com>

commit 6f691251c0350ac52a007c54bf3ef62e9d8cdc5e upstream.

We got the bug that qemu complained with "KVM: unknown exit, hardware
reason 31" and KVM shown these info:
[84245.284948] EPT: Misconfiguration.
[84245.285056] EPT: GPA: 0xfeda848
[84245.285154] ept_misconfig_inspect_spte: spte 0x5eaef50107 level 4
[84245.285344] ept_misconfig_inspect_spte: spte 0x5f5fadc107 level 3
[84245.285532] ept_misconfig_inspect_spte: spte 0x5141d18107 level 2
[84245.285723] ept_misconfig_inspect_spte: spte 0x52e40dad77 level 1

This is because we got a mmio #PF and the handler see the mmio spte becomes
normal (points to the ram page)

However, this is valid after introducing fast mmio spte invalidation which
increases the generation-number instead of zapping mmio sptes, a example
is as follows:
1. QEMU drops mmio region by adding a new memslot
2. invalidate all mmio sptes
3.

        VCPU 0                        VCPU 1
    access the invalid mmio spte
                            access the region originally was MMIO before
                            set the spte to the normal ram map

    mmio #PF
    check the spte and see it becomes normal ram mapping !!!

This patch fixes the bug just by dropping the check in mmio handler, it's
good for backport. Full check will be introduced in later patches

Reported-by: Pavel Shirshov <ru.pchel@gmail.com>
Tested-by: Pavel Shirshov <ru.pchel@gmail.com>
Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 arch/x86/kvm/mmu.c | 45 ---------------------------------------------
 1 file changed, 45 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index c8fb357..b479c50 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -376,12 +376,6 @@ static u64 __get_spte_lockless(u64 *sptep)
 {
 	return ACCESS_ONCE(*sptep);
 }
-
-static bool __check_direct_spte_mmio_pf(u64 spte)
-{
-	/* It is valid if the spte is zapped. */
-	return spte == 0ull;
-}
 #else
 union split_spte {
 	struct {
@@ -497,23 +491,6 @@ retry:
 
 	return spte.spte;
 }
-
-static bool __check_direct_spte_mmio_pf(u64 spte)
-{
-	union split_spte sspte = (union split_spte)spte;
-	u32 high_mmio_mask = shadow_mmio_mask >> 32;
-
-	/* It is valid if the spte is zapped. */
-	if (spte == 0ull)
-		return true;
-
-	/* It is valid if the spte is being zapped. */
-	if (sspte.spte_low == 0ull &&
-	    (sspte.spte_high & high_mmio_mask) == high_mmio_mask)
-		return true;
-
-	return false;
-}
 #endif
 
 static bool spte_is_locklessly_modifiable(u64 spte)
@@ -3209,21 +3186,6 @@ static bool quickly_check_mmio_pf(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 	return vcpu_match_mmio_gva(vcpu, addr);
 }
 
-
-/*
- * On direct hosts, the last spte is only allows two states
- * for mmio page fault:
- *   - It is the mmio spte
- *   - It is zapped or it is being zapped.
- *
- * This function completely checks the spte when the last spte
- * is not the mmio spte.
- */
-static bool check_direct_spte_mmio_pf(u64 spte)
-{
-	return __check_direct_spte_mmio_pf(spte);
-}
-
 static u64 walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr)
 {
 	struct kvm_shadow_walk_iterator iterator;
@@ -3266,13 +3228,6 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 	}
 
 	/*
-	 * It's ok if the gva is remapped by other cpus on shadow guest,
-	 * it's a BUG if the gfn is not a mmio page.
-	 */
-	if (direct && !check_direct_spte_mmio_pf(spte))
-		return RET_MMIO_PF_BUG;
-
-	/*
 	 * If the page table is zapped by other cpus, let CPU fault again on
 	 * the address.
 	 */
-- 
1.9.1

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[3.13.y-ckt stable] Linux 3.13.11-ckt28 stable review Kamal Mostafa <kamal@canonical.com> - 2015-10-20 23:40 +0200
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  [PATCH 3.13.y-ckt 51/85] drm/i915: Always mark the object as dirty when used by the GPU Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:40 +0200
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  [PATCH 3.13.y-ckt 68/85] powerpc/rtas: Introduce rtas_get_sensor_fast() for IRQ handlers Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:40 +0200
  [PATCH 3.13.y-ckt 47/85] Input: synaptics - fix handling of disabling gesture mode Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:40 +0200
    Re: [PATCH 3.13.y-ckt 47/85] Input: synaptics - fix handling of  disabling gesture mode Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2015-10-21 00:50 +0200
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  [PATCH 3.13.y-ckt 43/85] rtlwifi: rtl8192cu: Add new device ID Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:40 +0200
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  [PATCH 3.13.y-ckt 72/85] windfarm: decrement client count when unregistering Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:40 +0200
  [PATCH 3.13.y-ckt 22/85] NFSv4: don't set SETATTR for O_RDONLY|O_EXCL Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:40 +0200
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  [PATCH 3.13.y-ckt 30/85] xtensa: fix kernel register spilling Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 26/85] drivers: usb: fsl: Workaround for USB erratum-A005275 Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 36/85] HID: usbhid: Fix the check for HID_RESET_PENDING in hid_io_error Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
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  [PATCH 3.13.y-ckt 38/85] libxfs: readahead of dir3 data blocks should use the read verifier Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
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  [PATCH 3.13.y-ckt 31/85] NFS: nfs_set_pgio_error sometimes misses errors Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 44/85] rtlwifi: rtl8192cu: Add new device ID Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 45/85] of/address: Don't loop forever in of_find_matching_node_by_address(). Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 28/85] staging: comedi: adl_pci7x3x: fix digital output on PCI-7230 Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 39/85] xfs: Fix xfs_attr_leafblock definition Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
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  [PATCH 3.13.y-ckt 33/85] usb: host: ehci-sys: delete useless bus_to_hcd conversion Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 40/85] arm64: kconfig: Move LIST_POISON to a safe value Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 02/85] dcache: Handle escaped paths in prepend_path Kamal Mostafa <kamal@canonical.com> - 2015-10-21 00:50 +0200
  [PATCH 3.13.y-ckt 07/85] xtensa: fix threadptr reload on return to userspace Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 03/85] vfs: Test for and handle paths that are unreachable from their mnt_root Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 05/85] [media] v4l: omap3isp: Fix sub-device power management code Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 16/85] devres: fix devres_get() Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 08/85] ARM: OMAP2+: DRA7: clockdomain: change l4per2_7xx_clkdm to SW_WKUP Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 04/85] sctp: fix race on protocol/netns initialization Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 12/85] usb: dwc3: ep0: Fix mem corruption on OUT transfers of more than 512 bytes Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 14/85] KVM: MMU: fix validation of mmio page fault Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 11/85] PCI: Add VPD function 0 quirk for Intel Ethernet devices Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 10/85] PCI: Add dev_flags bit to access VPD through function 0 Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 15/85] auxdisplay: ks0108: fix refcount Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 09/85] mac80211: enable assoc check for mesh interfaces Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200
  [PATCH 3.13.y-ckt 13/85] serial: 8250_pci: Add support for Pericom PI7C9X795[1248] Kamal Mostafa <kamal@canonical.com> - 2015-10-21 01:00 +0200

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