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Message-ID: <20250313215540.4171762-2-yosry.ahmed@linux.dev>
Date: Thu, 13 Mar 2025 21:55:34 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Maxim Levitsky <mlevitsk@...hat.com>,
x86@...nel.org,
kvm@...r.kernel.org,
linux-kernel@...r.kernel.org,
Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH 1/7] KVM: VMX: Generalize VPID allocation to be vendor-neutral
Generalize the VMX VPID allocation code and make move it to common code
in preparation for sharing with SVM. Create a generic struct
kvm_tlb_tags, representing a factory for VPIDs (or ASIDs later), and use
one for VPIDs.
Most of the functionality remains the same, with the following
differences:
- The enable_vpid checks are moved to the callers for allocate_vpid()
and free_vpid(), as they are specific to VMX.
- The bitmap allocation is now dynamic (which will be required for SVM),
so it is initialized and cleaned up in vmx_hardware_{setup/unsetup}().
- The range of valid TLB tags is expressed in terms of min/max instead
of the number of tags to support SVM use cases.
Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
arch/x86/kvm/vmx/nested.c | 4 +--
arch/x86/kvm/vmx/vmx.c | 38 +++++--------------------
arch/x86/kvm/vmx/vmx.h | 4 +--
arch/x86/kvm/x86.c | 58 +++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/x86.h | 13 +++++++++
5 files changed, 82 insertions(+), 35 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index d06e50d9c0e79..b017bd2eb2382 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -343,7 +343,7 @@ static void free_nested(struct kvm_vcpu *vcpu)
vmx->nested.vmxon = false;
vmx->nested.smm.vmxon = false;
vmx->nested.vmxon_ptr = INVALID_GPA;
- free_vpid(vmx->nested.vpid02);
+ kvm_tlb_tags_free(&vmx_vpids, vmx->nested.vpid02);
vmx->nested.posted_intr_nv = -1;
vmx->nested.current_vmptr = INVALID_GPA;
if (enable_shadow_vmcs) {
@@ -5333,7 +5333,7 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)
HRTIMER_MODE_ABS_PINNED);
vmx->nested.preemption_timer.function = vmx_preemption_timer_fn;
- vmx->nested.vpid02 = allocate_vpid();
+ vmx->nested.vpid02 = enable_vpid ? kvm_tlb_tags_alloc(&vmx_vpids) : 0;
vmx->nested.vmcs02_initialized = false;
vmx->nested.vmxon = true;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b70ed72c1783d..f7ce75842fa26 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -496,8 +496,7 @@ DEFINE_PER_CPU(struct vmcs *, current_vmcs);
*/
static DEFINE_PER_CPU(struct list_head, loaded_vmcss_on_cpu);
-static DECLARE_BITMAP(vmx_vpid_bitmap, VMX_NR_VPIDS);
-static DEFINE_SPINLOCK(vmx_vpid_lock);
+struct kvm_tlb_tags vmx_vpids;
struct vmcs_config vmcs_config __ro_after_init;
struct vmx_capability vmx_capability __ro_after_init;
@@ -3972,31 +3971,6 @@ static void seg_setup(int seg)
vmcs_write32(sf->ar_bytes, ar);
}
-int allocate_vpid(void)
-{
- int vpid;
-
- if (!enable_vpid)
- return 0;
- spin_lock(&vmx_vpid_lock);
- vpid = find_first_zero_bit(vmx_vpid_bitmap, VMX_NR_VPIDS);
- if (vpid < VMX_NR_VPIDS)
- __set_bit(vpid, vmx_vpid_bitmap);
- else
- vpid = 0;
- spin_unlock(&vmx_vpid_lock);
- return vpid;
-}
-
-void free_vpid(int vpid)
-{
- if (!enable_vpid || vpid == 0)
- return;
- spin_lock(&vmx_vpid_lock);
- __clear_bit(vpid, vmx_vpid_bitmap);
- spin_unlock(&vmx_vpid_lock);
-}
-
static void vmx_msr_bitmap_l01_changed(struct vcpu_vmx *vmx)
{
/*
@@ -7559,7 +7533,7 @@ void vmx_vcpu_free(struct kvm_vcpu *vcpu)
if (enable_pml)
vmx_destroy_pml_buffer(vmx);
- free_vpid(vmx->vpid);
+ kvm_tlb_tags_free(&vmx_vpids, vmx->vpid);
nested_vmx_free_vcpu(vcpu);
free_loaded_vmcs(vmx->loaded_vmcs);
free_page((unsigned long)vmx->ve_info);
@@ -7578,7 +7552,7 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
err = -ENOMEM;
- vmx->vpid = allocate_vpid();
+ vmx->vpid = enable_vpid ? kvm_tlb_tags_alloc(&vmx_vpids) : 0;
/*
* If PML is turned on, failure on enabling PML just results in failure
@@ -7681,7 +7655,7 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
free_pml:
vmx_destroy_pml_buffer(vmx);
free_vpid:
- free_vpid(vmx->vpid);
+ kvm_tlb_tags_free(&vmx_vpids, vmx->vpid);
return err;
}
@@ -8373,6 +8347,7 @@ void vmx_hardware_unsetup(void)
nested_vmx_hardware_unsetup();
free_kvm_area();
+ kvm_tlb_tags_destroy(&vmx_vpids);
}
void vmx_vm_destroy(struct kvm *kvm)
@@ -8591,7 +8566,8 @@ __init int vmx_hardware_setup(void)
kvm_caps.has_bus_lock_exit = cpu_has_vmx_bus_lock_detection();
kvm_caps.has_notify_vmexit = cpu_has_notify_vmexit();
- set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */
+ /* VPID 0 is reserved for host, so min=1 */
+ kvm_tlb_tags_init(&vmx_vpids, 1, VMX_NR_VPIDS - 1);
if (enable_ept)
kvm_mmu_set_ept_masks(enable_ept_ad_bits,
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 951e44dc9d0ea..9bece3ea63eaa 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -376,10 +376,10 @@ struct kvm_vmx {
u64 *pid_table;
};
+extern struct kvm_tlb_tags vmx_vpids;
+
void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
struct loaded_vmcs *buddy);
-int allocate_vpid(void);
-void free_vpid(int vpid);
void vmx_set_constant_host_state(struct vcpu_vmx *vmx);
void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
void vmx_set_host_fs_gs(struct vmcs_host_state *host, u16 fs_sel, u16 gs_sel,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 69c20a68a3f01..182f18ebc62f3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13992,6 +13992,64 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
}
EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
+int kvm_tlb_tags_init(struct kvm_tlb_tags *tlb_tags, unsigned int min,
+ unsigned int max)
+{
+ /*
+ * 0 is assumed to be the host's TLB tag and is returned on failed
+ * allocations.
+ */
+ if (WARN_ON_ONCE(min == 0))
+ return -1;
+
+ /*
+ * Allocate enough bits to index the bitmap directly by the tag,
+ * potentially wasting a bit of memory.
+ */
+ tlb_tags->bitmap = bitmap_zalloc(max + 1, GFP_KERNEL);
+ if (!tlb_tags->bitmap)
+ return -1;
+
+ tlb_tags->min = min;
+ tlb_tags->max = max;
+ spin_lock_init(&tlb_tags->lock);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_tlb_tags_init);
+
+void kvm_tlb_tags_destroy(struct kvm_tlb_tags *tlb_tags)
+{
+ bitmap_free(tlb_tags->bitmap);
+}
+EXPORT_SYMBOL_GPL(kvm_tlb_tags_destroy);
+
+unsigned int kvm_tlb_tags_alloc(struct kvm_tlb_tags *tlb_tags)
+{
+ unsigned int tag;
+
+ spin_lock(&tlb_tags->lock);
+ tag = find_next_zero_bit(tlb_tags->bitmap, tlb_tags->max + 1,
+ tlb_tags->min);
+ if (tag <= tlb_tags->max)
+ __set_bit(tag, tlb_tags->bitmap);
+ else
+ tag = 0;
+ spin_unlock(&tlb_tags->lock);
+ return tag;
+}
+EXPORT_SYMBOL_GPL(kvm_tlb_tags_alloc);
+
+void kvm_tlb_tags_free(struct kvm_tlb_tags *tlb_tags, unsigned int tag)
+{
+ if (tag < tlb_tags->min || WARN_ON_ONCE(tag > tlb_tags->max))
+ return;
+
+ spin_lock(&tlb_tags->lock);
+ __clear_bit(tag, tlb_tags->bitmap);
+ spin_unlock(&tlb_tags->lock);
+}
+EXPORT_SYMBOL_GPL(kvm_tlb_tags_free);
+
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 9dc32a4090761..9f84e933d189b 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -652,4 +652,17 @@ int ____kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
+struct kvm_tlb_tags {
+ spinlock_t lock;
+ unsigned long *bitmap;
+ unsigned int min;
+ unsigned int max;
+};
+
+int kvm_tlb_tags_init(struct kvm_tlb_tags *tlb_tags, unsigned int min,
+ unsigned int max);
+void kvm_tlb_tags_destroy(struct kvm_tlb_tags *tlb_tags);
+unsigned int kvm_tlb_tags_alloc(struct kvm_tlb_tags *tlb_tags);
+void kvm_tlb_tags_free(struct kvm_tlb_tags *tlb_tags, unsigned int tag);
+
#endif
--
2.49.0.rc1.451.g8f38331e32-goog
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