RE: [PATCH v4 2/6] KVM: nVMX: Enable nested virtualize x2apic mode
From: Zhang, Yang Z
Date: Wed Jan 28 2015 - 21:54:37 EST
Wincy Van wrote on 2015-01-28:
> When L2 is using x2apic, we can use virtualize x2apic mode to gain higher
> performance, especially in apicv case.
>
> This patch also introduces nested_vmx_check_apicv_controls for the nested
> apicv patches.
>
> Signed-off-by: Wincy Van <fanwenyi0529@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 114
> +++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 files changed, 112 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 787f886..9d11a93
> 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1108,6 +1108,11 @@ static inline bool nested_cpu_has_xsaves(struct
> vmcs12 *vmcs12)
> vmx_xsaves_supported();
> }
>
> +static inline bool nested_cpu_has_virt_x2apic_mode(struct vmcs12
> +*vmcs12) {
> + return nested_cpu_has2(vmcs12,
> +SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE);
> +}
> +
> static inline bool is_exception(u32 intr_info) {
> return (intr_info & (INTR_INFO_INTR_TYPE_MASK |
> INTR_INFO_VALID_MASK)) @@ -2395,6 +2400,7 @@ static __init void
> nested_vmx_setup_ctls_msrs(void)
> nested_vmx_secondary_ctls_low = 0;
> nested_vmx_secondary_ctls_high &=
> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
> + SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
> SECONDARY_EXEC_WBINVD_EXITING |
> SECONDARY_EXEC_XSAVES;
>
> @@ -4155,6 +4161,52 @@ static void
> __vmx_enable_intercept_for_msr(unsigned long *msr_bitmap,
> }
> }
>
> +/*
> + * If a msr is allowed by L0, we should check whether it is allowed by L1.
> + * The corresponding bit will be cleared unless both of L0 and L1 allow it.
> + */
> +static void nested_vmx_disable_intercept_for_msr(unsigned long
> *msr_bitmap_l1,
> + unsigned long
> *msr_bitmap_nested,
> + u32 msr, int type) {
> + int f = sizeof(unsigned long);
> +
> + if (!cpu_has_vmx_msr_bitmap()) {
> + WARN_ON(1);
> + return;
> + }
> +
> + /*
> + * See Intel PRM Vol. 3, 20.6.9 (MSR-Bitmap Address). Early manuals
> + * have the write-low and read-high bitmap offsets the wrong way
> round.
> + * We can control MSRs 0x00000000-0x00001fff and
> 0xc0000000-0xc0001fff.
> + */
> + if (msr <= 0x1fff) {
> + if (type & MSR_TYPE_R &&
> + !test_bit(msr, msr_bitmap_l1 + 0x000 / f))
> + /* read-low */
> + __clear_bit(msr, msr_bitmap_nested + 0x000 / f);
> +
> + if (type & MSR_TYPE_W &&
> + !test_bit(msr, msr_bitmap_l1 + 0x800 / f))
> + /* write-low */
> + __clear_bit(msr, msr_bitmap_nested + 0x800 / f);
> +
> + } else if ((msr >= 0xc0000000) && (msr <= 0xc0001fff)) {
> + msr &= 0x1fff;
> + if (type & MSR_TYPE_R &&
> + !test_bit(msr, msr_bitmap_l1 + 0x400 / f))
> + /* read-high */
> + __clear_bit(msr, msr_bitmap_nested + 0x400 / f);
> +
> + if (type & MSR_TYPE_W &&
> + !test_bit(msr, msr_bitmap_l1 + 0xc00 / f))
> + /* write-high */
> + __clear_bit(msr, msr_bitmap_nested + 0xc00 / f);
> +
> + }
> +}
> +
> static void vmx_disable_intercept_for_msr(u32 msr, bool longmode_only) {
> if (!longmode_only)
> @@ -8350,7 +8402,59 @@ static int
> nested_vmx_check_msr_bitmap_controls(struct kvm_vcpu *vcpu, static
> inline bool nested_vmx_merge_msr_bitmap(struct kvm_vcpu *vcpu,
> struct vmcs12
> *vmcs12) {
> - return false;
> + struct page *page;
> + unsigned long *msr_bitmap;
> +
> + if (!nested_cpu_has_virt_x2apic_mode(vmcs12))
> + return false;
> +
> + page = nested_get_page(vcpu, vmcs12->msr_bitmap);
> + if (!page) {
> + WARN_ON(1);
> + return false;
> + }
> + msr_bitmap = (unsigned long *)kmap(page);
> + if (!msr_bitmap) {
> + nested_release_page_clean(page);
> + WARN_ON(1);
> + return false;
> + }
> +
> + if (nested_cpu_has_virt_x2apic_mode(vmcs12)) {
> + /* TPR is allowed */
> + nested_vmx_disable_intercept_for_msr(msr_bitmap,
> + vmx_msr_bitmap_nested,
> + APIC_BASE_MSR + (APIC_TASKPRI >>
> 4),
> + MSR_TYPE_R | MSR_TYPE_W);
> + } else
> + __vmx_enable_intercept_for_msr(
> + vmx_msr_bitmap_nested,
> + APIC_BASE_MSR + (APIC_TASKPRI >>
> 4),
> + MSR_TYPE_R | MSR_TYPE_W);
> + kunmap(page);
> + nested_release_page_clean(page);
> +
> + return true;
> +}
> +
> +static int nested_vmx_check_apicv_controls(struct kvm_vcpu *vcpu,
> + struct vmcs12 *vmcs12) {
> + if (!nested_cpu_has_virt_x2apic_mode(vmcs12))
> + return 0;
> +
> + /*
> + * If virtualize x2apic mode is enabled,
> + * virtualize apic access must be disabled.
> + */
> + if (nested_cpu_has2(vmcs12,
> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES))
> + return -EINVAL;
> +
> + /* tpr shadow is needed by all apicv features. */
> + if (!nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW))
> + return -EINVAL;
> +
> + return 0;
> }
>
> static int nested_vmx_check_msr_switch(struct kvm_vcpu *vcpu, @@
> -8646,7 +8750,8 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12)
> else
> vmcs_write64(APIC_ACCESS_ADDR,
>
> page_to_phys(vmx->nested.apic_access_page));
> - } else if
> (vm_need_virtualize_apic_accesses(vmx->vcpu.kvm)) {
> + } else if (!(nested_cpu_has_virt_x2apic_mode(vmcs12)) &&
> +
> + (vm_need_virtualize_apic_accesses(vmx->vcpu.kvm))) {
> exec_control |=
You don't load L2's apic_page in your patch correctly when x2apic mode is used. Here is the right change for prepare_vmcs02()(maybe other place also need change too):
@@ -8585,7 +8585,8 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
CPU_BASED_ACTIVATE_SECONDARY_CONTROLS))
exec_control |= vmcs12->secondary_vm_exec_control;
- if (exec_control & SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES) {
+ if (exec_control & (SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
+ SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) {
/*
* If translation failed, no matter: This feature asks
* to exit when accessing the given address, and if it
@@ -8594,7 +8595,8 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
*/
if (!vmx->nested.apic_access_page)
exec_control &=
- ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
+ ~ (SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
+ SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE);
else
vmcs_write64(APIC_ACCESS_ADDR,
page_to_phys(vmx->nested.apic_access_page));
Best regards,
Yang