diff mbox series

[v5,6/7] KVM: x86: Implement kvm_arch_vcpu_pre_fault_memory()

Message ID 20240710174031.312055-7-pbonzini@redhat.com (mailing list archive)
State New, archived
Headers show
Series KVM: Guest Memory Pre-Population API | expand

Commit Message

Paolo Bonzini July 10, 2024, 5:40 p.m. UTC 
Wire KVM_PRE_FAULT_MEMORY ioctl to __kvm_mmu_do_page_fault() to populate guest
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
process RET_PF_* return values and convert them to success or errno.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-ID: <9b866a0ae7147f96571c439e75429a03dcb659b6.1712785629.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/Kconfig   |  1 +
 arch/x86/kvm/mmu/mmu.c | 73 ++++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/x86.c     |  3 ++
 3 files changed, 77 insertions(+)

Comments

Binbin Wu July 11, 2024, 5:36 a.m. UTC | #1 
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@intel.com>
> Message-ID: <9b866a0ae7147f96571c439e75429a03dcb659b6.1712785629.git.isaku.yamahata@intel.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.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;
Paolo Bonzini July 11, 2024, 8:30 a.m. UTC | #2 
On Thu, Jul 11, 2024 at 7:37 AM Binbin Wu <binbin.wu@linux.intel.com> wrote:
> 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()?

Yes, will fix.

> > 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.

This is x86-specific code and it CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY
is always selected by CONFIG_KVM on x86 (that is, it does not depend
on TDX or anything else).

Paolo
diff mbox series

Patch

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
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 152b30fa22ad..4e0e9963066f 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4709,6 +4709,79 @@  int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	return direct_page_fault(vcpu, fault);
 }
 
+static int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
+			    u8 *level)
+{
+	int r;
+
+	/*
+	 * Restrict to TDP page fault, since that's the only case where the MMU
+	 * is indexed by GPA.
+	 */
+	if (vcpu->arch.mmu->page_fault != kvm_tdp_page_fault)
+		return -EOPNOTSUPP;
+
+	do {
+		if (signal_pending(current))
+			return -EINTR;
+		cond_resched();
+		r = kvm_mmu_do_page_fault(vcpu, gpa, error_code, true, NULL, level);
+	} while (r == RET_PF_RETRY);
+
+	if (r < 0)
+		return r;
+
+	switch (r) {
+	case RET_PF_FIXED:
+	case RET_PF_SPURIOUS:
+		return 0;
+
+	case RET_PF_EMULATE:
+		return -ENOENT;
+
+	case RET_PF_RETRY:
+	case RET_PF_CONTINUE:
+	case RET_PF_INVALID:
+	default:
+		WARN_ONCE(1, "could not fix page fault during prefault");
+		return -EIO;
+	}
+}
+
+long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
+				    struct kvm_pre_fault_memory *range)
+{
+	u64 error_code = PFERR_GUEST_FINAL_MASK;
+	u8 level = PG_LEVEL_4K;
+	u64 end;
+	int r;
+
+	/*
+	 * reload is efficient when called repeatedly, so we can do it on
+	 * every iteration.
+	 */
+	kvm_mmu_reload(vcpu);
+
+	if (kvm_arch_has_private_mem(vcpu->kvm) &&
+	    kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(range->gpa)))
+		error_code |= PFERR_PRIVATE_ACCESS;
+
+	/*
+	 * Shadow paging uses GVA for kvm page fault, so restrict to
+	 * two-dimensional paging.
+	 */
+	r = kvm_tdp_map_page(vcpu, range->gpa, error_code, &level);
+	if (r < 0)
+		return r;
+
+	/*
+	 * If the mapping that covers range->gpa can use a huge page, it
+	 * may start below it or end after range->gpa + range->size.
+	 */
+	end = (range->gpa & KVM_HPAGE_MASK(level)) + KVM_HPAGE_SIZE(level);
+	return min(range->size, end - range->gpa);
+}
+
 static void nonpaging_init_context(struct kvm_mmu *context)
 {
 	context->page_fault = nonpaging_page_fault;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
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;
 	case KVM_CAP_EXIT_HYPERCALL:
 		r = KVM_EXIT_HYPERCALL_VALID_MASK;
 		break;