linux-kernel - Re: [PATCH v7 048/102] KVM: x86/mmu: Disallow dirty logging for x86 TDX

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Date:   Fri, 08 Jul 2022 14:30:28 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH v7 048/102] KVM: x86/mmu: Disallow dirty logging for x86
 TDX

On Mon, 2022-06-27 at 14:53 -0700, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> TDX doesn't support dirty logging.  Report dirty logging isn't supported so
> that device model, for example qemu, can properly handle it.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>

Xiaoyao's SoB looks weird.

> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/x86.c       |  5 +++++
>  include/linux/kvm_host.h |  1 +
>  virt/kvm/kvm_main.c      | 15 ++++++++++++---
>  3 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4309ef0ade21..dcd1f5e2ba05 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -13164,6 +13164,11 @@ 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;
> +}
> +
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 79a4988fd51f..6fd8ec297236 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1452,6 +1452,7 @@ 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);
>  
>  #ifndef __KVM_HAVE_ARCH_VM_ALLOC
>  /*
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 7a5261eb7eb8..703c1d0c98da 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1467,9 +1467,18 @@ static void kvm_replace_memslot(struct kvm *kvm,
>  	}
>  }
>  
> -static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)
> +bool __weak kvm_arch_dirty_log_supported(struct kvm *kvm)
>  {
> -	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
> +	return true;
> +}
> +
> +static int check_memory_region_flags(struct kvm *kvm,
> +				     const struct kvm_userspace_memory_region *mem)
> +{
> +	u32 valid_flags = 0;
> +
> +	if (kvm_arch_dirty_log_supported(kvm))
> +		valid_flags |= KVM_MEM_LOG_DIRTY_PAGES;
>  
>  #ifdef __KVM_HAVE_READONLY_MEM
>  	valid_flags |= KVM_MEM_READONLY;
> @@ -1871,7 +1880,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
>  	int as_id, id;
>  	int r;
>  
> -	r = check_memory_region_flags(mem);
> +	r = check_memory_region_flags(kvm, mem);
>  	if (r)
>  		return r;
>