From: Wanpeng Li <[email protected]>
Pedro reported:
During tests that we conducted on KVM, we noticed that executing a "PUSH %ES"
instruction under KVM produces different results on both memory and the SP
register depending on whether EPT support is enabled. With EPT the SP is
reduced by 4 bytes (and the written value is 0-padded) but without EPT support
it is only reduced by 2 bytes. The difference can be observed when the CS.DB
field is 1 (32-bit) but not when it's 0 (16-bit).
The internal segment descriptor cache exist even in real/vm8096 mode. The CS.D
also should be respected instead of just default operand/address-size/66H
prefix/67H prefix during instruction decoding. This patch fixes it by also
adjusting operand/address-size according to CS.D.
Reported-by: Pedro Fonseca <[email protected]>
Tested-by: Pedro Fonseca <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Pedro Fonseca <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
v4 -> v5:
* cleanup patch subject/description
v3 -> v4:
* def_ad_bytes must be changed to 4
* separate X86EMUL_MODE_PROT16 altogether from the others
v2 -> v3:
* cleanup the codes
v1 -> v2:
* respect cs.d for real/vm8096, other modes have already
been considered in init_emulate_ctxt().
arch/x86/kvm/emulate.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8079d14..b4a87de 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5000,6 +5000,8 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
bool op_prefix = false;
bool has_seg_override = false;
struct opcode opcode;
+ u16 dummy;
+ struct desc_struct desc;
ctxt->memop.type = OP_NONE;
ctxt->memopp = NULL;
@@ -5018,6 +5020,11 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
switch (mode) {
case X86EMUL_MODE_REAL:
case X86EMUL_MODE_VM86:
+ def_op_bytes = def_ad_bytes = 2;
+ ctxt->ops->get_segment(ctxt, &dummy, &desc, NULL, VCPU_SREG_CS);
+ if (desc.d)
+ def_op_bytes = def_ad_bytes = 4;
+ break;
case X86EMUL_MODE_PROT16:
def_op_bytes = def_ad_bytes = 2;
break;
--
2.7.4
From 1583731419136270772@xxx Sat Nov 11 01:32:58 +0000 2017
X-GM-THRID: 1578557473088358418
X-Gmail-Labels: Inbox,Category Forums,HistoricalUnread
From: Wanpeng Li <[email protected]>
Commit 4f350c6dbcb (kvm: nVMX: Handle deferred early VMLAUNCH/VMRESUME failure
properly) can result in L1(run kvm-unit-tests/run_tests.sh vmx_controls in L1)
null pointer deference and also L0 calltrace when EPT=0 on both L0 and L1.
In L1:
BUG: unable to handle kernel paging request at ffffffffc015bf8f
IP: vmx_vcpu_run+0x202/0x510 [kvm_intel]
PGD 146e13067 P4D 146e13067 PUD 146e15067 PMD 3d2686067 PTE 3d4af9161
Oops: 0003 [#1] PREEMPT SMP
CPU: 2 PID: 1798 Comm: qemu-system-x86 Not tainted 4.14.0-rc4+ #6
RIP: 0010:vmx_vcpu_run+0x202/0x510 [kvm_intel]
Call Trace:
WARNING: kernel stack frame pointer at ffffb86f4988bc18 in qemu-system-x86:1798 has bad value 0000000000000002
In L0:
-----------[ cut here ]------------
WARNING: CPU: 6 PID: 4460 at /home/kernel/linux/arch/x86/kvm//vmx.c:9845 vmx_inject_page_fault_nested+0x130/0x140 [kvm_intel]
CPU: 6 PID: 4460 Comm: qemu-system-x86 Tainted: G OE 4.14.0-rc7+ #25
RIP: 0010:vmx_inject_page_fault_nested+0x130/0x140 [kvm_intel]
Call Trace:
paging64_page_fault+0x500/0xde0 [kvm]
? paging32_gva_to_gpa_nested+0x120/0x120 [kvm]
? nonpaging_page_fault+0x3b0/0x3b0 [kvm]
? __asan_storeN+0x12/0x20
? paging64_gva_to_gpa+0xb0/0x120 [kvm]
? paging64_walk_addr_generic+0x11a0/0x11a0 [kvm]
? lock_acquire+0x2c0/0x2c0
? vmx_read_guest_seg_ar+0x97/0x100 [kvm_intel]
? vmx_get_segment+0x2a6/0x310 [kvm_intel]
? sched_clock+0x1f/0x30
? check_chain_key+0x137/0x1e0
? __lock_acquire+0x83c/0x2420
? kvm_multiple_exception+0xf2/0x220 [kvm]
? debug_check_no_locks_freed+0x240/0x240
? debug_smp_processor_id+0x17/0x20
? __lock_is_held+0x9e/0x100
kvm_mmu_page_fault+0x90/0x180 [kvm]
kvm_handle_page_fault+0x15c/0x310 [kvm]
? __lock_is_held+0x9e/0x100
handle_exception+0x3c7/0x4d0 [kvm_intel]
vmx_handle_exit+0x103/0x1010 [kvm_intel]
? kvm_arch_vcpu_ioctl_run+0x1628/0x2e20 [kvm]
The commit avoids to load host state of vmcs12 as vmcs01's guest state
since vmcs12 is not modified (except for the VM-instruction error field)
if the checking of vmcs control area fails. However, the mmu context is
switched to nested mmu in prepare_vmcs02() and it will not be reloaded
since load_vmcs12_host_state() is skipped when nested VMLAUNCH/VMRESUME
fails. This patch fixes it by reloading mmu context when nested
VMLAUNCH/VMRESUME fails.
Reviewed-by: Jim Mattson <[email protected]>
Reviewed-by: Krish Sadhukhan <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Jim Mattson <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
v3 -> v4:
* move it to a new function load_vmcs12_mmu_host_state
arch/x86/kvm/vmx.c | 34 ++++++++++++++++++++++------------
1 file changed, 22 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6cf3972..8aefb91 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11259,6 +11259,24 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
kvm_clear_interrupt_queue(vcpu);
}
+static void load_vmcs12_mmu_host_state(struct kvm_vcpu *vcpu,
+ struct vmcs12 *vmcs12)
+{
+ u32 entry_failure_code;
+
+ nested_ept_uninit_mmu_context(vcpu);
+
+ /*
+ * Only PDPTE load can fail as the value of cr3 was checked on entry and
+ * couldn't have changed.
+ */
+ if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &entry_failure_code))
+ nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);
+
+ if (!enable_ept)
+ vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
+}
+
/*
* A part of what we need to when the nested L2 guest exits and we want to
* run its L1 parent, is to reset L1's guest state to the host state specified
@@ -11272,7 +11290,6 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
struct vmcs12 *vmcs12)
{
struct kvm_segment seg;
- u32 entry_failure_code;
if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_EFER)
vcpu->arch.efer = vmcs12->host_ia32_efer;
@@ -11299,17 +11316,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
vcpu->arch.cr4_guest_owned_bits = ~vmcs_readl(CR4_GUEST_HOST_MASK);
vmx_set_cr4(vcpu, vmcs12->host_cr4);
- nested_ept_uninit_mmu_context(vcpu);
-
- /*
- * Only PDPTE load can fail as the value of cr3 was checked on entry and
- * couldn't have changed.
- */
- if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &entry_failure_code))
- nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);
-
- if (!enable_ept)
- vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
+ load_vmcs12_mmu_host_state(vcpu, vmcs12);
if (enable_vpid) {
/*
@@ -11539,6 +11546,9 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
* accordingly.
*/
nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
+
+ load_vmcs12_mmu_host_state(vcpu, vmcs12);
+
/*
* The emulated instruction was already skipped in
* nested_vmx_run, but the updated RIP was never
--
2.7.4
From 1583316371817919972@xxx Mon Nov 06 11:35:58 +0000 2017
X-GM-THRID: 1583308197545497055
X-Gmail-Labels: Inbox,Category Forums,HistoricalUnread
From: Wanpeng Li <[email protected]>
According to the SDM, if the "load IA32_BNDCFGS" VM-entry controls is 1, the
following checks are performed on the field for the IA32_BNDCFGS MSR:
- Bits reserved in the IA32_BNDCFGS MSR must be 0.
- The linear address in bits 63:12 must be canonical.
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Jim Mattson <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
v5 -> v6:
* keep the right conjunct
v3 -> v4:
* simply condition
* use && instead of nested "if"s
arch/x86/kvm/vmx.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e6c8ffa..6cf3972 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -10805,6 +10805,11 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
return 1;
}
+ if ((vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS) &&
+ (is_noncanonical_address(vmcs12->guest_bndcfgs & PAGE_MASK, vcpu) ||
+ (vmcs12->guest_bndcfgs & MSR_IA32_BNDCFGS_RSVD)))
+ return 1;
+
return 0;
}
--
2.7.4
From 1582914530020539224@xxx Thu Nov 02 01:08:52 +0000 2017
X-GM-THRID: 1582914530020539224
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