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KVM: VMX: Unconditionally allocate root VMCSes during boot CPU bringup
Allocate the root VMCS (misleading called "vmxarea" and "kvm_area" in KVM) for each possible CPU during early boot CPU bringup, before early TDX initialization, so that TDX can eventually do VMXON on-demand (to make SEAMCALLs) without needing to load kvm-intel.ko. Allocate the pages early on, e.g. instead of trying to do so on-demand, to avoid having to juggle allocation failures at runtime. Opportunistically rename the per-CPU pointers to better reflect the role of the VMCS. Use Intel's "root VMCS" terminology, e.g. from various VMCS patents[1][2] and older SDMs, not the more opaque "VMXON region" used in recent versions of the SDM. While it's possible the VMCS passed to VMXON no longer serves as _the_ root VMCS on modern CPUs, it is still in effect a "root mode VMCS", as described in the patents. Link: https://patentimages.storage.googleapis.com/c7/e4/32/d7a7def5580667/WO2013101191A1.pdf [1] Link: https://patentimages.storage.googleapis.com/13/f6/8d/1361fab8c33373/US20080163205A1.pdf [2] Tested-by: Chao Gao <chao.gao@intel.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Tested-by: Sagi Shahar <sagis@google.com> Link: https://patch.msgid.link/20260214012702.2368778-5-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
parent
a1450a8156
commit
405b7c2793
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@ -2,10 +2,21 @@
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#ifndef _ASM_X86_VIRT_H
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#define _ASM_X86_VIRT_H
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#include <linux/types.h>
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#include <linux/percpu-defs.h>
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#include <asm/reboot.h>
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#if IS_ENABLED(CONFIG_KVM_X86)
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extern bool virt_rebooting;
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void __init x86_virt_init(void);
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#if IS_ENABLED(CONFIG_KVM_INTEL)
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DECLARE_PER_CPU(struct vmcs *, root_vmcs);
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#endif
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#else
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static __always_inline void x86_virt_init(void) {}
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#endif
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#endif /* _ASM_X86_VIRT_H */
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@ -71,6 +71,7 @@
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#include <asm/traps.h>
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#include <asm/sev.h>
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#include <asm/tdx.h>
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#include <asm/virt.h>
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#include <asm/posted_intr.h>
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#include <asm/runtime-const.h>
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@ -2151,6 +2152,7 @@ static __init void identify_boot_cpu(void)
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cpu_detect_tlb(&boot_cpu_data);
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setup_cr_pinning();
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x86_virt_init();
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tsx_init();
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tdx_init();
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lkgs_init();
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@ -580,7 +580,6 @@ noinline void invept_error(unsigned long ext, u64 eptp)
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vmx_insn_failed("invept failed: ext=0x%lx eptp=%llx\n", ext, eptp);
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}
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static DEFINE_PER_CPU(struct vmcs *, vmxarea);
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DEFINE_PER_CPU(struct vmcs *, current_vmcs);
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/*
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* We maintain a per-CPU linked-list of VMCS loaded on that CPU. This is needed
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@ -2934,6 +2933,9 @@ static bool __kvm_is_vmx_supported(void)
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return false;
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}
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if (!per_cpu(root_vmcs, cpu))
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return false;
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return true;
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}
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@ -3008,7 +3010,7 @@ static int kvm_cpu_vmxon(u64 vmxon_pointer)
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int vmx_enable_virtualization_cpu(void)
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{
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int cpu = raw_smp_processor_id();
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u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
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u64 phys_addr = __pa(per_cpu(root_vmcs, cpu));
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int r;
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if (cr4_read_shadow() & X86_CR4_VMXE)
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@ -3129,47 +3131,6 @@ int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs)
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return -ENOMEM;
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}
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static void free_kvm_area(void)
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{
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int cpu;
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for_each_possible_cpu(cpu) {
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free_vmcs(per_cpu(vmxarea, cpu));
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per_cpu(vmxarea, cpu) = NULL;
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}
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}
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static __init int alloc_kvm_area(void)
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{
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int cpu;
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for_each_possible_cpu(cpu) {
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struct vmcs *vmcs;
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vmcs = alloc_vmcs_cpu(false, cpu, GFP_KERNEL);
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if (!vmcs) {
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free_kvm_area();
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return -ENOMEM;
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}
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/*
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* When eVMCS is enabled, alloc_vmcs_cpu() sets
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* vmcs->revision_id to KVM_EVMCS_VERSION instead of
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* revision_id reported by MSR_IA32_VMX_BASIC.
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*
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* However, even though not explicitly documented by
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* TLFS, VMXArea passed as VMXON argument should
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* still be marked with revision_id reported by
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* physical CPU.
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*/
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if (kvm_is_using_evmcs())
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vmcs->hdr.revision_id = vmx_basic_vmcs_revision_id(vmcs_config.basic);
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per_cpu(vmxarea, cpu) = vmcs;
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}
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return 0;
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}
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static void fix_pmode_seg(struct kvm_vcpu *vcpu, int seg,
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struct kvm_segment *save)
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{
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@ -8566,8 +8527,6 @@ void vmx_hardware_unsetup(void)
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if (nested)
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nested_vmx_hardware_unsetup();
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free_kvm_area();
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}
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void vmx_vm_destroy(struct kvm *kvm)
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@ -8870,10 +8829,6 @@ __init int vmx_hardware_setup(void)
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return r;
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}
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r = alloc_kvm_area();
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if (r)
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goto err_kvm_area;
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kvm_set_posted_intr_wakeup_handler(pi_wakeup_handler);
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/*
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@ -8900,11 +8855,6 @@ __init int vmx_hardware_setup(void)
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kvm_caps.inapplicable_quirks &= ~KVM_X86_QUIRK_IGNORE_GUEST_PAT;
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return 0;
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err_kvm_area:
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if (nested)
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nested_vmx_hardware_unsetup();
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return r;
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}
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void vmx_exit(void)
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@ -1,7 +1,78 @@
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// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/cpu.h>
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#include <linux/cpumask.h>
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#include <linux/errno.h>
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#include <linux/kvm_types.h>
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#include <linux/list.h>
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#include <linux/percpu.h>
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#include <asm/perf_event.h>
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#include <asm/processor.h>
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#include <asm/virt.h>
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#include <asm/vmx.h>
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__visible bool virt_rebooting;
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EXPORT_SYMBOL_FOR_KVM(virt_rebooting);
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#if IS_ENABLED(CONFIG_KVM_INTEL)
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DEFINE_PER_CPU(struct vmcs *, root_vmcs);
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EXPORT_PER_CPU_SYMBOL(root_vmcs);
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static __init void x86_vmx_exit(void)
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{
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int cpu;
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for_each_possible_cpu(cpu) {
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free_page((unsigned long)per_cpu(root_vmcs, cpu));
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per_cpu(root_vmcs, cpu) = NULL;
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}
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}
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static __init int x86_vmx_init(void)
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{
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u64 basic_msr;
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u32 rev_id;
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int cpu;
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if (!cpu_feature_enabled(X86_FEATURE_VMX))
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return -EOPNOTSUPP;
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rdmsrq(MSR_IA32_VMX_BASIC, basic_msr);
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/* IA-32 SDM Vol 3B: VMCS size is never greater than 4kB. */
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if (WARN_ON_ONCE(vmx_basic_vmcs_size(basic_msr) > PAGE_SIZE))
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return -EIO;
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/*
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* Even if eVMCS is enabled (or will be enabled?), and even though not
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* explicitly documented by TLFS, the root VMCS passed to VMXON should
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* still be marked with the revision_id reported by the physical CPU.
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*/
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rev_id = vmx_basic_vmcs_revision_id(basic_msr);
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for_each_possible_cpu(cpu) {
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int node = cpu_to_node(cpu);
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struct page *page;
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struct vmcs *vmcs;
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page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
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if (!page) {
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x86_vmx_exit();
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return -ENOMEM;
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}
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vmcs = page_address(page);
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vmcs->hdr.revision_id = rev_id;
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per_cpu(root_vmcs, cpu) = vmcs;
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}
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return 0;
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}
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#else
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static __init int x86_vmx_init(void) { return -EOPNOTSUPP; }
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#endif
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void __init x86_virt_init(void)
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{
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x86_vmx_init();
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}
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