linux-kernel - [PATCH v5 5/8] KVM: x86: Support interrupt dispatch in x2APIC mode with APIC-write VM exit

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Date:   Fri, 31 Dec 2021 22:28:46 +0800
From:   Zeng Guang <guang.zeng@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kim Phillips <kim.phillips@....com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        Kai Huang <kai.huang@...el.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Robert Hu <robert.hu@...el.com>, Gao Chao <chao.gao@...el.com>,
        Zeng Guang <guang.zeng@...el.com>
Subject: [PATCH v5 5/8] KVM: x86: Support interrupt dispatch in x2APIC mode with APIC-write VM exit

In VMX non-root operation, new behavior applies to
virtualize WRMSR to vICR in x2APIC mode. Depending
on settings of the VM-execution controls, CPU would
produce APIC-write VM-exit following the 64-bit value
written to offset 300H on the virtual-APIC page(vICR).
KVM needs to retrieve the value written by CPU and
emulate the vICR write to deliver an interrupt.

Current KVM doesn't consider to handle the 64-bit setting
on vICR in trap-like APIC-write VM-exit. Because using
kvm_lapic_reg_write() to emulate writes to APIC_ICR requires
the APIC_ICR2 is already programmed correctly. But in the
above APIC-write VM-exit, CPU writes the whole 64 bits to
APIC_ICR rather than program higher 32 bits and lower 32
bits to APIC_ICR2 and APIC_ICR respectively. So, KVM needs
to retrieve the whole 64-bit value and program higher 32 bits
to APIC_ICR2 first.

Signed-off-by: Zeng Guang <guang.zeng@...el.com>
---
 arch/x86/kvm/lapic.c | 12 +++++++++---
 arch/x86/kvm/lapic.h |  5 +++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index f206fc35deff..3ce7142ba00e 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2186,15 +2186,21 @@ EXPORT_SYMBOL_GPL(kvm_lapic_set_eoi);
 /* emulate APIC access in a trap manner */
 void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset)
 {
-	u32 val = 0;
+	struct kvm_lapic *apic = vcpu->arch.apic;
+	u64 val = 0;
 
 	/* hw has done the conditional check and inst decode */
 	offset &= 0xff0;
 
-	kvm_lapic_reg_read(vcpu->arch.apic, offset, 4, &val);
+	/* exception dealing with 64bit data on vICR in x2apic mode */
+	if ((offset == APIC_ICR) && apic_x2apic_mode(apic)) {
+		val = kvm_lapic_get_reg64(apic, offset);
+		kvm_lapic_reg_write(apic, APIC_ICR2, (u32)(val>>32));
+	} else
+		kvm_lapic_reg_read(apic, offset, 4, &val);
 
 	/* TODO: optimize to just emulate side effect w/o one more write */
-	kvm_lapic_reg_write(vcpu->arch.apic, offset, val);
+	kvm_lapic_reg_write(apic, offset, (u32)val);
 }
 EXPORT_SYMBOL_GPL(kvm_apic_write_nodecode);
 
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 2b44e533fc8d..91864e401a64 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -158,6 +158,11 @@ static inline u32 kvm_lapic_get_reg(struct kvm_lapic *apic, int reg_off)
 	return *((u32 *) (apic->regs + reg_off));
 }
 
+static inline u64 kvm_lapic_get_reg64(struct kvm_lapic *apic, int reg_off)
+{
+	return *((u64 *) (apic->regs + reg_off));
+}
+
 static inline void __kvm_lapic_set_reg(char *regs, int reg_off, u32 val)
 {
 	*((u32 *) (regs + reg_off)) = val;
-- 
2.27.0