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From: David Woodhouse <dwmw2@infradead.org>
To: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Ankur Arora <ankur.a.arora@oracle.com>,
	Joao Martins <joao.m.martins@oracle.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Sean Christopherson <seanjc@google.com>,
	graf@amazon.com, iaslan@amazon.de, pdurrant@amazon.com,
	aagch@amazon.com, fandree@amazon.com, hch@infradead.org
Subject: [PATCH v4 01/16] KVM: x86/xen: fix Xen hypercall page msr handling
Date: Wed,  6 Jan 2021 00:22:59 +0000
Message-ID: <20210106002314.328380-2-dwmw2@infradead.org> (raw)
In-Reply-To: <20210106002314.328380-1-dwmw2@infradead.org>

From: Joao Martins <joao.m.martins@oracle.com>

Xen usually places its MSR at 0x40000000 or 0x40000200 depending on
whether it is running in viridian mode or not. Note that this is not
ABI guaranteed, so it is possible for Xen to advertise the MSR some
place else.

Given the way xen_hvm_config() is handled, if the former address is
selected, this will conflict with Hyper-V's MSR
(HV_X64_MSR_GUEST_OS_ID) which unconditionally uses the same address.

Given that the MSR location is arbitrary, move the xen_hvm_config()
handling to the top of kvm_set_msr_common() before falling through.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 arch/x86/kvm/x86.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3f7c1fc7a3ce..f219d50b3700 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3007,6 +3007,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	u32 msr = msr_info->index;
 	u64 data = msr_info->data;
 
+	if (msr && msr == vcpu->kvm->arch.xen_hvm_config.msr)
+		return xen_hvm_config(vcpu, data);
+
 	switch (msr) {
 	case MSR_AMD64_NB_CFG:
 	case MSR_IA32_UCODE_WRITE:
@@ -3294,8 +3297,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vcpu->arch.msr_misc_features_enables = data;
 		break;
 	default:
-		if (msr && (msr == vcpu->kvm->arch.xen_hvm_config.msr))
-			return xen_hvm_config(vcpu, data);
 		if (kvm_pmu_is_valid_msr(vcpu, msr))
 			return kvm_pmu_set_msr(vcpu, msr_info);
 		return KVM_MSR_RET_INVALID;
-- 
2.29.2


  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-06  0:22 [PATCH v4 00/16] KVM: Add minimal support for Xen HVM guests David Woodhouse
2021-01-06  0:22 ` David Woodhouse [this message]
2021-01-06  0:23 ` [PATCH v4 02/16] KVM: x86/xen: intercept xen hypercalls if enabled David Woodhouse
2021-01-06  0:23 ` [PATCH v4 03/16] KVM: x86/xen: Fix coexistence of Xen and Hyper-V hypercalls David Woodhouse
2021-01-06  0:23 ` [PATCH v4 04/16] KVM: x86/xen: add KVM_XEN_HVM_SET_ATTR/KVM_XEN_HVM_GET_ATTR David Woodhouse
2021-01-06  0:23 ` [PATCH v4 05/16] KVM: x86/xen: latch long_mode when hypercall page is set up David Woodhouse
2021-01-06  0:23 ` [PATCH v4 06/16] KVM: x86/xen: add definitions of compat_shared_info, compat_vcpu_info David Woodhouse
2021-01-06  0:23 ` [PATCH v4 07/16] KVM: x86/xen: register shared_info page David Woodhouse
2021-01-06  0:23 ` [PATCH v4 08/16] xen: add wc_sec_hi to struct shared_info David Woodhouse
2021-01-06  0:23 ` [PATCH v4 09/16] KVM: x86/xen: update wallclock region David Woodhouse
2021-01-06  0:23 ` [PATCH v4 10/16] KVM: x86/xen: register vcpu info David Woodhouse
2021-01-06  0:23 ` [PATCH v4 11/16] KVM: x86/xen: setup pvclock updates David Woodhouse
2021-01-06  0:23 ` [PATCH v4 12/16] KVM: x86/xen: register vcpu time info region David Woodhouse
2021-01-06  0:23 ` [PATCH v4 13/16] KVM: x86/xen: register runstate info David Woodhouse
2021-01-06  0:23 ` [PATCH v4 14/16] KVM: x86: declare Xen HVM shared info capability and add test case David Woodhouse
2021-01-06  0:23 ` [PATCH v4 15/16] KVM: Add documentation for Xen hypercall and shared_info updates David Woodhouse
2021-01-06  0:23 ` [PATCH v4 16/16] KVM: x86/xen: Add event channel interrupt vector upcall David Woodhouse

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