Revert back to refreshing vmcs.HOST_CR3 immediately prior to VM-Enter.
The PCID (ASID) part of CR3 can be bumped without KVM being scheduled
out, as the kernel will switch CR3 during __text_poke(), e.g. in response
to a static key toggling. If switch_mm_irqs_off() chooses a new ASID for
the mm associate with KVM, KVM will do VM-Enter => VM-Exit with a stale
vmcs.HOST_CR3.
Add a comment to explain why KVM must wait until VM-Enter is imminent to
refresh vmcs.HOST_CR3.
The following splat was captured by stashing vmcs.HOST_CR3 in kvm_vcpu
and adding a WARN in load_new_mm_cr3() to fire if a new ASID is being
loaded for the KVM-associated mm while KVM has a "running" vCPU:
static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, bool need_flush)
{
struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
...
WARN(vcpu && (vcpu->cr3 & GENMASK(11, 0)) != (new_mm_cr3 & GENMASK(11, 0)) &&
(vcpu->cr3 & PHYSICAL_PAGE_MASK) == (new_mm_cr3 & PHYSICAL_PAGE_MASK),
"KVM is hosed, loading CR3 = %lx, vmcs.HOST_CR3 = %lx", new_mm_cr3, vcpu->cr3);
}
------------[ cut here ]------------
KVM is hosed, loading CR3 =
8000000105393004, vmcs.HOST_CR3 =
105393003
WARNING: CPU: 4 PID: 20717 at arch/x86/mm/tlb.c:291 load_new_mm_cr3+0x82/0xe0
Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel
CPU: 4 PID: 20717 Comm: stable Tainted: G W 5.17.0-rc3+ #747
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:load_new_mm_cr3+0x82/0xe0
RSP: 0018:
ffffc9000489fa98 EFLAGS:
00010082
RAX:
0000000000000000 RBX:
8000000105393004 RCX:
0000000000000027
RDX:
0000000000000027 RSI:
00000000ffffdfff RDI:
ffff888277d1b788
RBP:
0000000000000004 R08:
ffff888277d1b780 R09:
ffffc9000489f8b8
R10:
0000000000000001 R11:
0000000000000001 R12:
0000000000000000
R13:
ffff88810678a800 R14:
0000000000000004 R15:
0000000000000c33
FS:
00007fa9f0e72700(0000) GS:
ffff888277d00000(0000) knlGS:
0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
CR2:
0000000000000000 CR3:
00000001001b5003 CR4:
0000000000172ea0
Call Trace:
<TASK>
switch_mm_irqs_off+0x1cb/0x460
__text_poke+0x308/0x3e0
text_poke_bp_batch+0x168/0x220
text_poke_finish+0x1b/0x30
arch_jump_label_transform_apply+0x18/0x30
static_key_slow_inc_cpuslocked+0x7c/0x90
static_key_slow_inc+0x16/0x20
kvm_lapic_set_base+0x116/0x190
kvm_set_apic_base+0xa5/0xe0
kvm_set_msr_common+0x2f4/0xf60
vmx_set_msr+0x355/0xe70 [kvm_intel]
kvm_set_msr_ignored_check+0x91/0x230
kvm_emulate_wrmsr+0x36/0x120
vmx_handle_exit+0x609/0x6c0 [kvm_intel]
kvm_arch_vcpu_ioctl_run+0x146f/0x1b80
kvm_vcpu_ioctl+0x279/0x690
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK>
---[ end trace
0000000000000000 ]---
This reverts commit
15ad9762d69fd8e40a4a51828c1d6b0c1b8fbea0.
Fixes: 15ad9762d69f ("KVM: VMX: Save HOST_CR3 in vmx_prepare_switch_to_guest()")
Reported-by: Wanpeng Li <kernellwp@gmail.com>
Cc: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Acked-by: Lai Jiangshan <jiangshanlai@gmail.com>
Message-Id: <
20220224191917.
3508476-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- unsigned long cr4;
+ unsigned long cr3, cr4;
bool vm_fail;
if (!nested_early_check)
*/
vmcs_writel(GUEST_RFLAGS, 0);
+ cr3 = __get_current_cr3_fast();
+ if (unlikely(cr3 != vmx->loaded_vmcs->host_state.cr3)) {
+ vmcs_writel(HOST_CR3, cr3);
+ vmx->loaded_vmcs->host_state.cr3 = cr3;
+ }
+
cr4 = cr4_read_shadow();
if (unlikely(cr4 != vmx->loaded_vmcs->host_state.cr4)) {
vmcs_writel(HOST_CR4, cr4);
#ifdef CONFIG_X86_64
int cpu = raw_smp_processor_id();
#endif
- unsigned long cr3;
unsigned long fs_base, gs_base;
u16 fs_sel, gs_sel;
int i;
#endif
vmx_set_host_fs_gs(host_state, fs_sel, gs_sel, fs_base, gs_base);
-
- /* Host CR3 including its PCID is stable when guest state is loaded. */
- cr3 = __get_current_cr3_fast();
- if (unlikely(cr3 != host_state->cr3)) {
- vmcs_writel(HOST_CR3, cr3);
- host_state->cr3 = cr3;
- }
-
vmx->guest_state_loaded = true;
}
static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- unsigned long cr4;
+ unsigned long cr3, cr4;
/* Record the guest's net vcpu time for enforced NMI injections. */
if (unlikely(!enable_vnmi &&
vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);
vcpu->arch.regs_dirty = 0;
+ /*
+ * Refresh vmcs.HOST_CR3 if necessary. This must be done immediately
+ * prior to VM-Enter, as the kernel may load a new ASID (PCID) any time
+ * it switches back to the current->mm, which can occur in KVM context
+ * when switching to a temporary mm to patch kernel code, e.g. if KVM
+ * toggles a static key while handling a VM-Exit.
+ */
+ cr3 = __get_current_cr3_fast();
+ if (unlikely(cr3 != vmx->loaded_vmcs->host_state.cr3)) {
+ vmcs_writel(HOST_CR3, cr3);
+ vmx->loaded_vmcs->host_state.cr3 = cr3;
+ }
+
cr4 = cr4_read_shadow();
if (unlikely(cr4 != vmx->loaded_vmcs->host_state.cr4)) {
vmcs_writel(HOST_CR4, cr4);