* Re: [PATCH] KVM: VMX: Report up-to-date exit qualification to userspace
2023-12-29 2:26 [PATCH] KVM: VMX: Report up-to-date exit qualification to userspace Chao Gao
@ 2024-02-07 16:04 ` Sean Christopherson
2024-02-09 0:22 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2024-02-07 16:04 UTC (permalink / raw)
To: Chao Gao
Cc: kvm, Paolo Bonzini, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, linux-kernel
On Fri, Dec 29, 2023, Chao Gao wrote:
> Use vmx_get_exit_qual() to read the exit qualification.
>
> vcpu->arch.exit_qualification is cached for EPT violation only and even
> for EPT violation, it is stale at this point because the up-to-date
> value is cached later in handle_ept_violation().
Oof, vcpu->arch.exit_qualification is *gross*. At a glance, it should be
straightforward to get rid of it and use the fault structure to pass the info
that comes from the MMU. I'll post a patch, assuming it works.
As for this patch, I'll get it applied for 6.9.
---
arch/x86/include/asm/kvm_host.h | 3 ---
arch/x86/kvm/kvm_emulate.h | 1 +
arch/x86/kvm/mmu/paging_tmpl.h | 14 +++++++-------
arch/x86/kvm/vmx/nested.c | 5 ++++-
arch/x86/kvm/vmx/vmx.c | 2 --
5 files changed, 12 insertions(+), 13 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ad5319a503f0..7ef4715d43d6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -993,9 +993,6 @@ struct kvm_vcpu_arch {
u64 msr_kvm_poll_control;
- /* set at EPT violation at this point */
- unsigned long exit_qualification;
-
/* pv related host specific info */
struct {
bool pv_unhalted;
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 4351149484fb..b5791a66637e 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -26,6 +26,7 @@ struct x86_exception {
bool nested_page_fault;
u64 address; /* cr2 or nested page fault gpa */
u8 async_page_fault;
+ unsigned long exit_qualification;
};
/*
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 4d4e98fe4f35..7a87097cb45b 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -497,21 +497,21 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
* The other bits are set to 0.
*/
if (!(errcode & PFERR_RSVD_MASK)) {
- vcpu->arch.exit_qualification &= (EPT_VIOLATION_GVA_IS_VALID |
- EPT_VIOLATION_GVA_TRANSLATED);
+ walker->fault.exit_qualification = 0;
+
if (write_fault)
- vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_WRITE;
+ walker->fault.exit_qualification |= EPT_VIOLATION_ACC_WRITE;
if (user_fault)
- vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_READ;
+ walker->fault.exit_qualification |= EPT_VIOLATION_ACC_READ;
if (fetch_fault)
- vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_INSTR;
+ walker->fault.exit_qualification |= EPT_VIOLATION_ACC_INSTR;
/*
* Note, pte_access holds the raw RWX bits from the EPTE, not
* ACC_*_MASK flags!
*/
- vcpu->arch.exit_qualification |= (pte_access & VMX_EPT_RWX_MASK) <<
- EPT_VIOLATION_RWX_SHIFT;
+ walker->fault.exit_qualification |= (pte_access & VMX_EPT_RWX_MASK) <<
+ EPT_VIOLATION_RWX_SHIFT;
}
#endif
walker->fault.address = addr;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 994e014f8a50..15141b08c604 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -407,10 +407,13 @@ static void nested_ept_invalidate_addr(struct kvm_vcpu *vcpu, gpa_t eptp,
static void nested_ept_inject_page_fault(struct kvm_vcpu *vcpu,
struct x86_exception *fault)
{
+ unsigned long exit_qualification = fault->exit_qualification;
struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
struct vcpu_vmx *vmx = to_vmx(vcpu);
u32 vm_exit_reason;
- unsigned long exit_qualification = vcpu->arch.exit_qualification;
+
+ exit_qualification |= vmx_get_exit_qual(vcpu) &
+ (EPT_VIOLATION_GVA_IS_VALID | EPT_VIOLATION_GVA_TRANSLATED);
if (vmx->nested.pml_full) {
vm_exit_reason = EXIT_REASON_PML_FULL;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e262bc2ba4e5..1de022af7dcb 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5771,8 +5771,6 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
error_code |= (exit_qualification & EPT_VIOLATION_GVA_TRANSLATED) != 0 ?
PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK;
- vcpu->arch.exit_qualification = exit_qualification;
-
/*
* Check that the GPA doesn't exceed physical memory limits, as that is
* a guest page fault. We have to emulate the instruction here, because
base-commit: 873eef46b33c86be414d60bd00390e64fc0f006f
--
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: VMX: Report up-to-date exit qualification to userspace
2023-12-29 2:26 [PATCH] KVM: VMX: Report up-to-date exit qualification to userspace Chao Gao
2024-02-07 16:04 ` Sean Christopherson
@ 2024-02-09 0:22 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2024-02-09 0:22 UTC (permalink / raw)
To: Sean Christopherson, kvm, Chao Gao
Cc: Paolo Bonzini, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, linux-kernel
On Fri, 29 Dec 2023 10:26:52 +0800, Chao Gao wrote:
> Use vmx_get_exit_qual() to read the exit qualification.
>
> vcpu->arch.exit_qualification is cached for EPT violation only and even
> for EPT violation, it is stale at this point because the up-to-date
> value is cached later in handle_ept_violation().
>
>
> [...]
Applied to kvm-x86 vmx, thanks!
[1/1] KVM: VMX: Report up-to-date exit qualification to userspace
https://github.com/kvm-x86/linux/commit/d7f0a00e438d
--
https://github.com/kvm-x86/linux/tree/next
^ permalink raw reply [flat|nested] 3+ messages in thread