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x86/KVM/VMX: Use MSR save list for IA32_FLUSH_CMD if required

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If the L1D flush module parameter is set to 'always' and the IA32_FLUSH_CMD
MSR is available, optimize the VMENTER code with the MSR save list.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Konrad Rzeszutek Wilk 2018-06-28 17:10:36 -04:00 committed by Thomas Gleixner
parent 989e3992d2
commit 390d975e0c
1 changed files with 37 additions and 5 deletions
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42
arch/x86/kvm/vmx.c
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@ -6237,6 +6237,16 @@ static void ept_set_mmio_spte_mask(void)
VMX_EPT_MISCONFIG_WX_VALUE);
}
static bool vmx_l1d_use_msr_save_list(void)
{
if (!enable_ept || !boot_cpu_has_bug(X86_BUG_L1TF) ||
static_cpu_has(X86_FEATURE_HYPERVISOR) ||
!static_cpu_has(X86_FEATURE_FLUSH_L1D))
return false;
return vmentry_l1d_flush == VMENTER_L1D_FLUSH_ALWAYS;
}
#define VMX_XSS_EXIT_BITMAP 0
/*
* Sets up the vmcs for emulated real mode.
@ -6358,6 +6368,12 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
vmcs_write64(PML_ADDRESS, page_to_phys(vmx->pml_pg));
vmcs_write16(GUEST_PML_INDEX, PML_ENTITY_NUM - 1);
}
/*
* If flushing the L1D cache on every VMENTER is enforced and the
* MSR is available, use the MSR save list.
*/
if (vmx_l1d_use_msr_save_list())
add_atomic_switch_msr(vmx, MSR_IA32_FLUSH_CMD, L1D_FLUSH, 0, true);
}
static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
@ -9607,11 +9623,26 @@ static void vmx_l1d_flush(struct kvm_vcpu *vcpu)
bool always;
/*
* If the mitigation mode is 'flush always', keep the flush bit
* set, otherwise clear it. It gets set again either from
* vcpu_run() or from one of the unsafe VMEXIT handlers.
* This code is only executed when:
* - the flush mode is 'cond'
* - the flush mode is 'always' and the flush MSR is not
* available
*
* If the CPU has the flush MSR then clear the flush bit because
* 'always' mode is handled via the MSR save list.
*
* If the MSR is not avaibable then act depending on the mitigation
* mode: If 'flush always', keep the flush bit set, otherwise clear
* it.
*
* The flush bit gets set again either from vcpu_run() or from one
* of the unsafe VMEXIT handlers.
*/
always = vmentry_l1d_flush == VMENTER_L1D_FLUSH_ALWAYS;
if (static_cpu_has(X86_FEATURE_FLUSH_L1D))
always = false;
else
always = vmentry_l1d_flush == VMENTER_L1D_FLUSH_ALWAYS;
vcpu->arch.l1tf_flush_l1d = always;
vcpu->stat.l1d_flush++;
@ -13205,7 +13236,8 @@ static int __init vmx_setup_l1d_flush(void)
struct page *page;
if (vmentry_l1d_flush == VMENTER_L1D_FLUSH_NEVER ||
!boot_cpu_has_bug(X86_BUG_L1TF))
!boot_cpu_has_bug(X86_BUG_L1TF) ||
vmx_l1d_use_msr_save_list())
return 0;
if (!boot_cpu_has(X86_FEATURE_FLUSH_L1D)) {