linux-kernel - Re: [PATCH v2 06/10] KVM: x86: Implement kvm_arch_vcpu_map

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Message-ID: <Zh94V8ochIXEkO17@chao-email>
Date: Wed, 17 Apr 2024 15:20:55 +0800
From: Chao Gao <chao.gao@...el.com>
To: <isaku.yamahata@...el.com>
CC: <kvm@...r.kernel.org>, <isaku.yamahata@...il.com>,
	<linux-kernel@...r.kernel.org>, Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>, Michael Roth <michael.roth@....com>,
	David Matlack <dmatlack@...gle.com>, Federico Parola
	<federico.parola@...ito.it>, Kai Huang <kai.huang@...el.com>
Subject: Re: [PATCH v2 06/10] KVM: x86: Implement kvm_arch_vcpu_map_memory()

On Wed, Apr 10, 2024 at 03:07:32PM -0700, isaku.yamahata@...el.com wrote:
>From: Isaku Yamahata <isaku.yamahata@...el.com>
>
>Wire KVM_MAP_MEMORY ioctl to kvm_mmu_map_tdp_page() to populate guest
>memory.  When KVM_CREATE_VCPU creates vCPU, it initializes the x86
>KVM MMU part by kvm_mmu_create() and kvm_init_mmu().  vCPU is ready to
>invoke the KVM page fault handler.
>
>Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
>---
>v2:
>- Catch up the change of struct kvm_memory_mapping. (Sean)
>- Removed mapping level check. Push it down into vendor code. (David, Sean)
>- Rename goal_level to level. (Sean)
>- Drop kvm_arch_pre_vcpu_map_memory(), directly call kvm_mmu_reload().
>  (David, Sean)
>- Fixed the update of mapping.
>---
> arch/x86/kvm/x86.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
>diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>index 2d2619d3eee4..2c765de3531e 100644
>--- a/arch/x86/kvm/x86.c
>+++ b/arch/x86/kvm/x86.c
>@@ -4713,6 +4713,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> 	case KVM_CAP_VM_DISABLE_NX_HUGE_PAGES:
> 	case KVM_CAP_IRQFD_RESAMPLE:
> 	case KVM_CAP_MEMORY_FAULT_INFO:
>+	case KVM_CAP_MAP_MEMORY:
> 		r = 1;
> 		break;
> 	case KVM_CAP_EXIT_HYPERCALL:
>@@ -5867,6 +5868,35 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
> 	}
> }
> 
>+int kvm_arch_vcpu_map_memory(struct kvm_vcpu *vcpu,
>+			     struct kvm_memory_mapping *mapping)
>+{
>+	u64 end, error_code = 0;
>+	u8 level = PG_LEVEL_4K;

IIUC, no need to initialize @level here.

>+	int r;
>+
>+	/*
>+	 * Shadow paging uses GVA for kvm page fault.  The first implementation
>+	 * supports GPA only to avoid confusion.
>+	 */
>+	if (!tdp_enabled)
>+		return -EOPNOTSUPP;

This check duplicates the one for vcpu->arch.mmu->page_fault() in patch 5.

>+
>+	/* reload is optimized for repeated call. */
>+	kvm_mmu_reload(vcpu);
>+
>+	r = kvm_tdp_map_page(vcpu, mapping->base_address, error_code, &level);
>+	if (r)
>+		return r;
>+
>+	/* mapping->base_address is not necessarily aligned to level-hugepage. */
>+	end = (mapping->base_address & KVM_HPAGE_MASK(level)) +
>+		KVM_HPAGE_SIZE(level);

maybe
	end = ALIGN(mapping->base_address, KVM_HPAGE_SIZE(level));

>+	mapping->size -= end - mapping->base_address;
>+	mapping->base_address = end;
>+	return r;
>+}
>+
> long kvm_arch_vcpu_ioctl(struct file *filp,
> 			 unsigned int ioctl, unsigned long arg)
> {
>-- 
>2.43.2
>
>