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Message-Id: <20211019153214.109519-4-senozhatsky@chromium.org>
Date: Wed, 20 Oct 2021 00:32:14 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Paolo Bonzini <pbonzini@...hat.com>,
David Matlack <dmatlack@...gle.com>
Cc: 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>,
Suleiman Souhlal <suleiman@...gle.com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org,
Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: [PATCHV2 3/3] KVM: x86: add KVM_SET_MMU_PREFETCH ioctl
This ioctl lets user-space set the number of PTEs KVM will
prefetch:
- pte_prefetch 8
VM-EXIT Samples Samples% Time% Min Time Max Time Avg time
EPT_VIOLATION 760998 54.85% 7.23% 0.92us 31765.89us 7.78us ( +- 1.46% )
MSR_WRITE 170599 12.30% 0.53% 0.60us 3334.13us 2.52us ( +- 0.86% )
EXTERNAL_INTERRUPT 159510 11.50% 1.65% 0.49us 43705.81us 8.45us ( +- 7.54% )
[..]
Total Samples:1387305, Total events handled time:81900258.99us.
- pte_prefetch 16
VM-EXIT Samples Samples% Time% Min Time Max Time Avg time
EPT_VIOLATION 658064 52.58% 7.04% 0.91us 17022.84us 8.34us ( +- 1.52% )
MSR_WRITE 163776 13.09% 0.54% 0.56us 5192.10us 2.57us ( +- 1.25% )
EXTERNAL_INTERRUPT 144588 11.55% 1.62% 0.48us 97410.16us 8.75us ( +- 11.44% )
[..]
Total Samples:1251546, Total events handled time:77956187.56us.
Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
Documentation/virt/kvm/api.rst | 21 +++++++++++++++++++++
arch/x86/kvm/x86.c | 29 +++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 4 ++++
3 files changed, 54 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 0c0bf26426b3..b06b7c11a430 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5473,6 +5473,17 @@ the trailing ``'\0'``, is indicated by ``name_size`` in the header.
The Stats Data block contains an array of 64-bit values in the same order
as the descriptors in Descriptors block.
+4.134 KVM SET MMU PREFETCH
+----------------------
+
+:Capability: KVM_CAP_MMU PREFETCH
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: int value (in)
+:Returns: 0 on success, error code otherwise
+
+Sets the maximum number of PTEs KVM will try to prefetch.
+
5. The kvm_run structure
========================
@@ -7440,3 +7451,13 @@ The argument to KVM_ENABLE_CAP is also a bitmask, and must be a subset
of the result of KVM_CHECK_EXTENSION. KVM will forward to userspace
the hypercalls whose corresponding bit is in the argument, and return
ENOSYS for the others.
+
+8.35 KVM_CAP_MMU_PTE_PREFETCH
+---------------------------
+
+:Capability: KVM_CAP_MMU_PTE_PREFETCH
+:Architectures: x86
+:Parameters: args[0] - the number of PTEs to prefetch
+
+Sets the maximum number of PTEs KVM will prefetch. The value must be power
+of two and within (0, 128] range.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4805960a89e6..e1b2224c4176 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4030,6 +4030,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_VM_COPY_ENC_CONTEXT_FROM:
case KVM_CAP_SREGS2:
case KVM_CAP_EXIT_ON_EMULATION_FAILURE:
+ case KVM_CAP_MMU_PTE_PREFETCH:
r = 1;
break;
case KVM_CAP_EXIT_HYPERCALL:
@@ -5831,6 +5832,25 @@ int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long state)
}
#endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */
+static int kvm_arch_mmu_pte_prefetch(struct kvm *kvm, unsigned int num_pages)
+{
+ struct kvm_vcpu *vcpu;
+ int i, ret;
+
+ mutex_lock(&kvm->lock);
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ ret = kvm_set_pte_prefetch(vcpu, num_pages);
+ if (ret) {
+ kvm_err("Failed to set PTE prefetch on VCPU%d: %d\n",
+ vcpu->vcpu_id, ret);
+ break;
+ }
+ }
+ mutex_unlock(&kvm->lock);
+
+ return ret;
+}
+
static int kvm_vm_ioctl_get_clock(struct kvm *kvm, void __user *argp)
{
struct kvm_clock_data data;
@@ -6169,6 +6189,15 @@ long kvm_arch_vm_ioctl(struct file *filp,
case KVM_X86_SET_MSR_FILTER:
r = kvm_vm_ioctl_set_msr_filter(kvm, argp);
break;
+ case KVM_SET_MMU_PREFETCH: {
+ u64 val;
+
+ r = -EFAULT;
+ if (copy_from_user(&val, argp, sizeof(val)))
+ goto out;
+ r = kvm_arch_mmu_pte_prefetch(kvm, val);
+ break;
+ }
default:
r = -ENOTTY;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 322b4b588d75..0782eb4c424d 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1120,6 +1120,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_BINARY_STATS_FD 203
#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
#define KVM_CAP_ARM_MTE 205
+#define KVM_CAP_MMU_PTE_PREFETCH 206
#ifdef KVM_CAP_IRQ_ROUTING
@@ -2015,4 +2016,7 @@ struct kvm_stats_desc {
#define KVM_GET_STATS_FD _IO(KVMIO, 0xce)
+/* Set number of PTEs to prefetch */
+#define KVM_SET_MMU_PREFETCH _IOW(KVMIO, 0xcf, __u64)
+
#endif /* __LINUX_KVM_H */
--
2.33.0.1079.g6e70778dc9-goog
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