KVM: nVMX: Add a helper to get highest pending from Posted Interrupt vector

Add a helper to retrieve the highest pending vector given a Posted
Interrupt descriptor.  While the actual operation is straightforward, it's
surprisingly easy to mess up, e.g. if one tries to reuse lapic.c's
find_highest_vector(), which doesn't work with PID.PIR due to the APIC's
IRR and ISR component registers being physically discontiguous (they're
4-byte registers aligned at 16-byte intervals).

To make PIR handling more consistent with respect to IRR and ISR handling,
return -1 to indicate "no interrupt pending".

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240607172609.3205077-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 643935a0f70ab77b8de56e1c0a145211af5af2ed..8f4db6e8f57c728b93e33fc282da2ba7b33e45ce 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -12,6 +12,7 @@
 #include "mmu.h"
 #include "nested.h"
 #include "pmu.h"
+#include "posted_intr.h"
 #include "sgx.h"
 #include "trace.h"
 #include "vmx.h"
@@ -3899,8 +3900,8 @@ static int vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
        if (!pi_test_and_clear_on(vmx->nested.pi_desc))
                return 0;
 
-       max_irr = find_last_bit((unsigned long *)vmx->nested.pi_desc->pir, 256);
-       if (max_irr != 256) {
+       max_irr = pi_find_highest_vector(vmx->nested.pi_desc);
+       if (max_irr > 0) {
                vapic_page = vmx->nested.virtual_apic_map.hva;
                if (!vapic_page)
                        goto mmio_needed;

diff --git a/arch/x86/kvm/vmx/posted_intr.h b/arch/x86/kvm/vmx/posted_intr.h
index 6b2a0226257ea148fa958fa6f18f39d2f281ecc6..1715d2ab07be5d40bb2eeb38c58d6a89285ef240 100644 (file)
--- a/arch/x86/kvm/vmx/posted_intr.h
+++ b/arch/x86/kvm/vmx/posted_intr.h
@@ -1,6 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef __KVM_X86_VMX_POSTED_INTR_H
 #define __KVM_X86_VMX_POSTED_INTR_H
+
+#include <linux/find.h>
 #include <asm/posted_intr.h>
 
 void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu);
@@ -12,4 +14,12 @@ int vmx_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
                       uint32_t guest_irq, bool set);
 void vmx_pi_start_assignment(struct kvm *kvm);
 
+static inline int pi_find_highest_vector(struct pi_desc *pi_desc)
+{
+       int vec;
+
+       vec = find_last_bit((unsigned long *)pi_desc->pir, 256);
+       return vec < 256 ? vec : -1;
+}
+
 #endif /* __KVM_X86_VMX_POSTED_INTR_H */