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x86/kvm/vmx: Move guest enter/exit into .noinstr.text 

Move the functions which are inside the RCU off region into the
non-instrumentable text section.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Message-Id: <20200708195322.037311579@linutronix.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Thomas Gleixner 2020-07-08 21:51:57 +02:00 committed by Paolo Bonzini
parent 9fc975e9ef
commit 3ebccdf373
6 changed files with 81 additions and 53 deletions
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4
arch/x86/include/asm/hardirq.h
View File

@ -67,12 +67,12 @@ static inline void kvm_set_cpu_l1tf_flush_l1d(void)
__this_cpu_write(irq_stat.kvm_cpu_l1tf_flush_l1d, 1);
}
static inline void kvm_clear_cpu_l1tf_flush_l1d(void)
static __always_inline void kvm_clear_cpu_l1tf_flush_l1d(void)
{
__this_cpu_write(irq_stat.kvm_cpu_l1tf_flush_l1d, 0);
}
static inline bool kvm_get_cpu_l1tf_flush_l1d(void)
static __always_inline bool kvm_get_cpu_l1tf_flush_l1d(void)
{
return __this_cpu_read(irq_stat.kvm_cpu_l1tf_flush_l1d);
}

8
arch/x86/include/asm/kvm_host.h
View File

@ -1598,7 +1598,15 @@ asmlinkage void kvm_spurious_fault(void);
insn "\n\t" \
"jmp 668f \n\t" \
"667: \n\t" \
"1: \n\t" \
".pushsection .discard.instr_begin \n\t" \
".long 1b - . \n\t" \
".popsection \n\t" \
"call kvm_spurious_fault \n\t" \
"1: \n\t" \
".pushsection .discard.instr_end \n\t" \
".long 1b - . \n\t" \
".popsection \n\t" \
"668: \n\t" \
_ASM_EXTABLE(666b, 667b)

4
arch/x86/kvm/vmx/ops.h
View File

@ -146,7 +146,9 @@ do { \
: : op1 : "cc" : error, fault); \
return; \
error: \
instrumentation_begin(); \
insn##_error(error_args); \
instrumentation_end(); \
return; \
fault: \
kvm_spurious_fault(); \
@ -161,7 +163,9 @@ do { \
: : op1, op2 : "cc" : error, fault); \
return; \
error: \
instrumentation_begin(); \
insn##_error(error_args); \
instrumentation_end(); \
return; \
fault: \
kvm_spurious_fault(); \

5
arch/x86/kvm/vmx/vmenter.S
View File

@ -27,7 +27,7 @@
#define VCPU_R15 __VCPU_REGS_R15 * WORD_SIZE
#endif
.text
.section .noinstr.text, "ax"
/**
* vmx_vmenter - VM-Enter the current loaded VMCS
@ -234,6 +234,9 @@ SYM_FUNC_START(__vmx_vcpu_run)
jmp 1b
SYM_FUNC_END(__vmx_vcpu_run)
.section .text, "ax"
/**
* vmread_error_trampoline - Trampoline from inline asm to vmread_error()
* @field: VMCS field encoding that failed

111
arch/x86/kvm/vmx/vmx.c
View File

@ -6116,7 +6116,7 @@ unexpected_vmexit:
* information but as all relevant affected CPUs have 32KiB L1D cache size
* there is no point in doing so.
*/
static void vmx_l1d_flush(struct kvm_vcpu *vcpu)
static noinstr void vmx_l1d_flush(struct kvm_vcpu *vcpu)
{
int size = PAGE_SIZE << L1D_CACHE_ORDER;
@ -6149,7 +6149,7 @@ static void vmx_l1d_flush(struct kvm_vcpu *vcpu)
vcpu->stat.l1d_flush++;
if (static_cpu_has(X86_FEATURE_FLUSH_L1D)) {
wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
native_wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
return;
}
@ -6635,7 +6635,7 @@ static void vmx_update_hv_timer(struct kvm_vcpu *vcpu)
}
}
void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
void noinstr vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
{
if (unlikely(host_rsp != vmx->loaded_vmcs->host_state.rsp)) {
vmx->loaded_vmcs->host_state.rsp = host_rsp;
@ -6657,6 +6657,63 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
struct vcpu_vmx *vmx)
{
/*
* VMENTER enables interrupts (host state), but the kernel state is
* interrupts disabled when this is invoked. Also tell RCU about
* it. This is the same logic as for exit_to_user_mode().
*
* This ensures that e.g. latency analysis on the host observes
* guest mode as interrupt enabled.
*
* guest_enter_irqoff() informs context tracking about the
* transition to guest mode and if enabled adjusts RCU state
* accordingly.
*/
instrumentation_begin();
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare(CALLER_ADDR0);
instrumentation_end();
guest_enter_irqoff();
lockdep_hardirqs_on(CALLER_ADDR0);
/* L1D Flush includes CPU buffer clear to mitigate MDS */
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
else if (static_branch_unlikely(&mds_user_clear))
mds_clear_cpu_buffers();
if (vcpu->arch.cr2 != read_cr2())
write_cr2(vcpu->arch.cr2);
vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
vmx->loaded_vmcs->launched);
vcpu->arch.cr2 = read_cr2();
/*
* VMEXIT disables interrupts (host state), but tracing and lockdep
* have them in state 'on' as recorded before entering guest mode.
* Same as enter_from_user_mode().
*
* guest_exit_irqoff() restores host context and reinstates RCU if
* enabled and required.
*
* This needs to be done before the below as native_read_msr()
* contains a tracepoint and x86_spec_ctrl_restore_host() calls
* into world and some more.
*/
lockdep_hardirqs_off(CALLER_ADDR0);
guest_exit_irqoff();
instrumentation_begin();
trace_hardirqs_off_finish();
instrumentation_end();
}
static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
{
fastpath_t exit_fastpath;
@ -6731,52 +6788,8 @@ reenter_guest:
*/
x86_spec_ctrl_set_guest(vmx->spec_ctrl, 0);
/*
* VMENTER enables interrupts (host state), but the kernel state is
* interrupts disabled when this is invoked. Also tell RCU about
* it. This is the same logic as for exit_to_user_mode().
*
* This ensures that e.g. latency analysis on the host observes
* guest mode as interrupt enabled.
*
* guest_enter_irqoff() informs context tracking about the
* transition to guest mode and if enabled adjusts RCU state
* accordingly.
*/
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare(CALLER_ADDR0);
guest_enter_irqoff();
lockdep_hardirqs_on(CALLER_ADDR0);
/* L1D Flush includes CPU buffer clear to mitigate MDS */
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
else if (static_branch_unlikely(&mds_user_clear))
mds_clear_cpu_buffers();
if (vcpu->arch.cr2 != read_cr2())
write_cr2(vcpu->arch.cr2);
vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
vmx->loaded_vmcs->launched);
vcpu->arch.cr2 = read_cr2();
/*
* VMEXIT disables interrupts (host state), but tracing and lockdep
* have them in state 'on' as recorded before entering guest mode.
* Same as enter_from_user_mode().
*
* guest_exit_irqoff() restores host context and reinstates RCU if
* enabled and required.
*
* This needs to be done before the below as native_read_msr()
* contains a tracepoint and x86_spec_ctrl_restore_host() calls
* into world and some more.
*/
lockdep_hardirqs_off(CALLER_ADDR0);
guest_exit_irqoff();
trace_hardirqs_off_finish();
/* The actual VMENTER/EXIT is in the .noinstr.text section. */
vmx_vcpu_enter_exit(vcpu, vmx);
/*
* We do not use IBRS in the kernel. If this vCPU has used the

2
arch/x86/kvm/x86.c
View File

@ -402,7 +402,7 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
}
EXPORT_SYMBOL_GPL(kvm_set_apic_base);
asmlinkage __visible void kvm_spurious_fault(void)
asmlinkage __visible noinstr void kvm_spurious_fault(void)
{
/* Fault while not rebooting. We want the trace. */
BUG_ON(!kvm_rebooting);