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KVM: VMX: Extend VMXs #AC interceptor to handle split lock #AC in guest

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Two types of #AC can be generated in Intel CPUs:
 1. legacy alignment check #AC
 2. split lock #AC

Reflect #AC back into the guest if the guest has legacy alignment checks
enabled or if split lock detection is disabled.

If the #AC is not a legacy one and split lock detection is enabled, then
invoke handle_guest_split_lock() which will either warn and disable split
lock detection for this task or force SIGBUS on it.

[ tglx: Switch it to handle_guest_split_lock() and rename the misnamed
  helper function. ]

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lkml.kernel.org/r/20200410115517.176308876@linutronix.de
This commit is contained in:
Xiaoyao Li 2020-04-10 13:54:02 +02:00 committed by Borislav Petkov
parent 9de6fe3c28
commit e6f8b6c12f
1 changed files with 34 additions and 3 deletions
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37
arch/x86/kvm/vmx/vmx.c
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@ -4588,6 +4588,26 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
return 1;
}
/*
* If the host has split lock detection disabled, then #AC is
* unconditionally injected into the guest, which is the pre split lock
* detection behaviour.
*
* If the host has split lock detection enabled then #AC is
* only injected into the guest when:
* - Guest CPL == 3 (user mode)
* - Guest has #AC detection enabled in CR0
* - Guest EFLAGS has AC bit set
*/
static inline bool guest_inject_ac(struct kvm_vcpu *vcpu)
{
if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
return true;
return vmx_get_cpl(vcpu) == 3 && kvm_read_cr0_bits(vcpu, X86_CR0_AM) &&
(kvm_get_rflags(vcpu) & X86_EFLAGS_AC);
}
static int handle_exception_nmi(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@ -4653,9 +4673,6 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
return handle_rmode_exception(vcpu, ex_no, error_code);
switch (ex_no) {
case AC_VECTOR:
kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);
return 1;
case DB_VECTOR:
dr6 = vmcs_readl(EXIT_QUALIFICATION);
if (!(vcpu->guest_debug &
@ -4684,6 +4701,20 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;
kvm_run->debug.arch.exception = ex_no;
break;
case AC_VECTOR:
if (guest_inject_ac(vcpu)) {
kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);
return 1;
}
/*
* Handle split lock. Depending on detection mode this will
* either warn and disable split lock detection for this
* task or force SIGBUS on it.
*/
if (handle_guest_split_lock(kvm_rip_read(vcpu)))
return 1;
fallthrough;
default:
kvm_run->exit_reason = KVM_EXIT_EXCEPTION;
kvm_run->ex.exception = ex_no;