* [PATCH] KVM: VMX: update PFEC_MASK/PFEC_MATCH together with PF intercept
@ 2020-10-03 8:48 Paolo Bonzini
0 siblings, 0 replies; only message in thread
From: Paolo Bonzini @ 2020-10-03 8:48 UTC (permalink / raw)
To: linux-kernel, kvm; +Cc: Qian Cai, Naresh Kamboju
The PFEC_MASK and PFEC_MATCH fields in the VMCS reverse the meaning of
the #PF intercept bit in the exception bitmap when they do not match.
This means that, if PFEC_MASK and/or PFEC_MATCH are set, the
hypervisor can get a vmexit for #PF exceptions even when the
corresponding bit is clear in the exception bitmap.
This is unexpected and is promptly detected by a WARN_ON_ONCE.
To fix it, reset PFEC_MASK and PFEC_MATCH when the #PF intercept
is disabled (as is common with enable_ept && !allow_smaller_maxphyaddr).
Reported-by: Qian Cai <cai@redhat.com>>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/vmx/vmx.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f0384e93548a..f4e9c310032a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -794,6 +794,18 @@ void update_exception_bitmap(struct kvm_vcpu *vcpu)
*/
if (is_guest_mode(vcpu))
eb |= get_vmcs12(vcpu)->exception_bitmap;
+ else {
+ /*
+ * If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched
+ * between guest and host. In that case we only care about present
+ * faults. For vmcs02, however, PFEC_MASK and PFEC_MATCH are set in
+ * prepare_vmcs02_rare.
+ */
+ bool selective_pf_trap = enable_ept && (eb & (1u << PF_VECTOR));
+ int mask = selective_pf_trap ? PFERR_PRESENT_MASK : 0;
+ vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, mask);
+ vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, mask);
+ }
vmcs_write32(EXCEPTION_BITMAP, eb);
}
@@ -4355,16 +4367,6 @@ static void init_vmcs(struct vcpu_vmx *vmx)
vmx->pt_desc.guest.output_mask = 0x7F;
vmcs_write64(GUEST_IA32_RTIT_CTL, 0);
}
-
- /*
- * If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched
- * between guest and host. In that case we only care about present
- * faults.
- */
- if (enable_ept) {
- vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, PFERR_PRESENT_MASK);
- vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, PFERR_PRESENT_MASK);
- }
}
static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
--
2.26.2
^ permalink raw reply related [flat|nested] only message in thread
only message in thread, other threads:[~2020-10-03 8:48 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-03 8:48 [PATCH] KVM: VMX: update PFEC_MASK/PFEC_MATCH together with PF intercept Paolo Bonzini
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).