linux-kernel - [PATCH 11/11] KVM: Disallow dirty logging for x86 TDX

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Date:   Fri, 12 Nov 2021 23:37:33 +0800
From:   Xiaoyao Li <xiaoyao.li@...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>
Cc:     xiaoyao.li@...el.com, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        isaku.yamahata@...el.com, Kai Huang <kai.huang@...el.com>
Subject: [PATCH 11/11] KVM: Disallow dirty logging for x86 TDX

From: Sean Christopherson <sean.j.christopherson@...el.com>

TDX doesn't support dirty logging for now.

Suggested-by: Kai Huang <kai.huang@...el.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
---

Do we need to introduce a VM-scope CAP to report if dirty log is supported?
since in the future, next generation of TDX will support live migration.
---
 arch/x86/kvm/x86.c       |  5 +++++
 include/linux/kvm_host.h |  1 +
 virt/kvm/kvm_main.c      | 10 +++++++++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f091a4d3c8f2..c30933289b54 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12611,6 +12611,11 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
 }
 EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
 
+bool kvm_arch_dirty_log_supported(struct kvm *kvm)
+{
+	return kvm->arch.vm_type != KVM_X86_TDX_VM;
+}
+
 bool kvm_arch_support_readonly_mem(struct kvm *kvm)
 {
 	return kvm->arch.vm_type != KVM_X86_TDX_VM;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1dbabf199c13..5f3debcd4295 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1071,6 +1071,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu);
 int kvm_arch_post_init_vm(struct kvm *kvm);
 void kvm_arch_pre_destroy_vm(struct kvm *kvm);
 int kvm_arch_create_vm_debugfs(struct kvm *kvm);
+bool kvm_arch_dirty_log_supported(struct kvm *kvm);
 bool kvm_arch_support_readonly_mem(struct kvm *kvm);
 
 #ifndef __KVM_HAVE_ARCH_VM_ALLOC
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c288c92a9c82..4c9d1e7834eb 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1421,6 +1421,11 @@ static void update_memslots(struct kvm_memslots *slots,
 	}
 }
 
+bool __weak kvm_arch_dirty_log_supported(struct kvm *kvm)
+{
+	return true;
+}
+
 bool __weak kvm_arch_support_readonly_mem(struct kvm *kvm)
 {
 #ifdef __KVM_HAVE_READONLY_MEM
@@ -1433,7 +1438,10 @@ bool __weak kvm_arch_support_readonly_mem(struct kvm *kvm)
 static int check_memory_region_flags(struct kvm *kvm,
 				     const struct kvm_userspace_memory_region *mem)
 {
-	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
+	u32 valid_flags = 0;
+
+	if (kvm_arch_dirty_log_supported(kvm))
+		valid_flags |= KVM_MEM_LOG_DIRTY_PAGES;
 
 	if (kvm_arch_support_readonly_mem(kvm))
 		valid_flags |= KVM_MEM_READONLY;
-- 
2.27.0