linux-kernel - [PATCH RFC 2/6] KVM: x86: extend struct kvm_vcpu_pv_apf

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Message-Id: <20200429093634.1514902-3-vkuznets@redhat.com>
Date:   Wed, 29 Apr 2020 11:36:30 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     x86@...nel.org, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: [PATCH RFC 2/6] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info

Currently, APF mechanism relies on the #PF abuse where the token is being
passed through CR2. If we switch to using interrupts to deliver page-ready
notifications we need a different way to pass the data. Extent the existing
'struct kvm_vcpu_pv_apf_data' with token information.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/include/uapi/asm/kvm_para.h |  3 ++-
 arch/x86/kvm/x86.c                   | 10 ++++++----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 2a8e0b6b9805..df2ba34037a2 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -113,7 +113,8 @@ struct kvm_mmu_op_release_pt {
 
 struct kvm_vcpu_pv_apf_data {
 	__u32 reason;
-	__u8 pad[60];
+	__u32 token;
+	__u8 pad[56];
 	__u32 enabled;
 };
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b93133ee07ba..7c21c0cf0a33 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2662,7 +2662,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
 	}
 
 	if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa,
-					sizeof(u32)))
+					sizeof(u64)))
 		return 1;
 
 	vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
@@ -10352,8 +10352,9 @@ static void kvm_del_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
 	}
 }
 
-static int apf_put_user(struct kvm_vcpu *vcpu, u32 val)
+static int apf_put_user(struct kvm_vcpu *vcpu, u32 reason, u32 token)
 {
+	u64 val = (u64)token << 32 | reason;
 
 	return kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.apf.data, &val,
 				      sizeof(val));
@@ -10405,7 +10406,8 @@ void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
 	kvm_add_async_pf_gfn(vcpu, work->arch.gfn);
 
 	if (kvm_can_deliver_async_pf(vcpu) &&
-	    !apf_put_user(vcpu, KVM_PV_REASON_PAGE_NOT_PRESENT)) {
+	    !apf_put_user(vcpu, KVM_PV_REASON_PAGE_NOT_PRESENT,
+			  work->arch.token)) {
 		fault.vector = PF_VECTOR;
 		fault.error_code_valid = true;
 		fault.error_code = 0;
@@ -10438,7 +10440,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
 	trace_kvm_async_pf_ready(work->arch.token, work->cr2_or_gpa);
 
 	if (vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED &&
-	    !apf_put_user(vcpu, KVM_PV_REASON_PAGE_READY)) {
+	    !apf_put_user(vcpu, KVM_PV_REASON_PAGE_READY, work->arch.token)) {
 			fault.vector = PF_VECTOR;
 			fault.error_code_valid = true;
 			fault.error_code = 0;
-- 
2.25.3