linux-kernel - Re: [PATCH v5 6/7] KVM: x86: Implement kvm_arch_vcpu_pre_fault

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Message-ID: <cd52fe00-b57b-495c-b55c-54fd381f7c66@linux.intel.com>
Date: Thu, 11 Jul 2024 13:36:56 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org
Cc: isaku.yamahata@...el.com, seanjc@...gle.com, xiaoyao.li@...el.com
Subject: Re: [PATCH v5 6/7] KVM: x86: Implement
 kvm_arch_vcpu_pre_fault_memory()



On 7/11/2024 1:40 AM, Paolo Bonzini wrote:
> Wire KVM_PRE_FAULT_MEMORY ioctl to __kvm_mmu_do_page_fault() to populate guest

__kvm_mmu_do_page_fault() -> kvm_mmu_do_page_fault()



> memory.  It can be called right after KVM_CREATE_VCPU creates a vCPU,
> since at that point kvm_mmu_create() and kvm_init_mmu() are called and
> the vCPU is ready to invoke the KVM page fault handler.
>
> The helper function kvm_mmu_map_tdp_page take care of the logic to

kvm_mmu_map_tdp_page -> kvm_tdp_map_page()?



> process RET_PF_* return values and convert them to success or errno.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Message-ID: <9b866a0ae7147f96571c439e75429a03dcb659b6.1712785629.git.isaku.yamahata@...el.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>   arch/x86/kvm/Kconfig   |  1 +
>   arch/x86/kvm/mmu/mmu.c | 73 ++++++++++++++++++++++++++++++++++++++++++
>   arch/x86/kvm/x86.c     |  3 ++
>   3 files changed, 77 insertions(+)
>
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index 80e5afde69f4..4287a8071a3a 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -44,6 +44,7 @@ config KVM
>   	select KVM_VFIO
>   	select HAVE_KVM_PM_NOTIFIER if PM
>   	select KVM_GENERIC_HARDWARE_ENABLING
> +	select KVM_GENERIC_PRE_FAULT_MEMORY
>   	select KVM_WERROR if WERROR
>   	help
>   	  Support hosting fully virtualized guest machines using hardware
[...]
> index ba0ad76f53bc..a6968eadd418 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4705,6 +4705,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>   	case KVM_CAP_MEMORY_FAULT_INFO:
>   		r = 1;
>   		break;
> +	case KVM_CAP_PRE_FAULT_MEMORY:
> +		r = tdp_enabled;
> +		break;
If !CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY, this should return 0.

>   	case KVM_CAP_EXIT_HYPERCALL:
>   		r = KVM_EXIT_HYPERCALL_VALID_MASK;
>   		break;