Re: [PATCH] KVM: VMX: use same MSR bitmaps for 32-/64-bit modes, fix MSR bitmaps for processor tracing

From: Paolo Bonzini
Date: Mon Jan 08 2018 - 18:11:37 EST

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In reply to: Jim Mattson: "Re: [PATCH] KVM: VMX: use same MSR bitmaps for 32-/64-bit modes, fix MSR bitmaps for processor tracing"
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----- Original Message -----
> From: "Jim Mattson" <jmattson@xxxxxxxxxx>
> To: "Paolo Bonzini" <pbonzini@xxxxxxxxxx>
> Cc: "LKML" <linux-kernel@xxxxxxxxxxxxxxx>, "kvm list" <kvm@xxxxxxxxxxxxxxx>, "Luwei Kang" <luwei.kang@xxxxxxxxx>
> Sent: Monday, January 8, 2018 10:23:41 PM
> Subject: Re: [PATCH] KVM: VMX: use same MSR bitmaps for 32-/64-bit modes, fix MSR bitmaps for processor tracing
>
> I would like to campaign for removing all of the precomputed MSR
> permission bitmaps, and using a separate bitmap for each vCPU, a la
> svm.c.

As usual, patches are welcome. :)

Paolo

> On Fri, Jan 5, 2018 at 7:43 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> > KVM has a small optimization where it doesn't save/restore
> > MSR_KERNEL_GS_BASE if the guest is in 32-bit mode. However,
> > this complicates the code noticeably by doubling the number of
> > possible MSR bitmaps. In addition, pt_disable_intercept_for_msr
> > was only updating the "basic" MSR bitmap, because x2apic and
> > x2apic_apicv are memcpy'd just once in hardware_setup.
> >
> > Remove the long-mode bitmaps set, and touch all the three remaining
> > bitmaps in vmx_disable_intercept_for_msr and vmx_enable_intercept_for_msr.
> >
> > Fixes: 3bd1f85e893daec4f3982d1d45b6bfc0683442c4
> > Cc: Luwei Kang <luwei.kang@xxxxxxxxx>
> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/vmx.c | 126
> > ++++++++++++++++++++---------------------------------
> > 1 file changed, 48 insertions(+), 78 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index 11321cc4129a..ea5b52dc2d78 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -935,12 +935,9 @@ static bool nested_vmx_is_page_fault_vmexit(struct
> > vmcs12 *vmcs12,
> > static DEFINE_PER_CPU(spinlock_t, blocked_vcpu_on_cpu_lock);
> >
> > enum {
> > - VMX_MSR_BITMAP_LEGACY,
> > - VMX_MSR_BITMAP_LONGMODE,
> > - VMX_MSR_BITMAP_LEGACY_X2APIC_APICV,
> > - VMX_MSR_BITMAP_LONGMODE_X2APIC_APICV,
> > - VMX_MSR_BITMAP_LEGACY_X2APIC,
> > - VMX_MSR_BITMAP_LONGMODE_X2APIC,
> > + VMX_MSR_BITMAP_NOX2APIC,
> > + VMX_MSR_BITMAP_X2APIC_APICV,
> > + VMX_MSR_BITMAP_X2APIC,
> > VMX_VMREAD_BITMAP,
> > VMX_VMWRITE_BITMAP,
> > VMX_BITMAP_NR
> > @@ -948,12 +945,9 @@ enum {
> >
> > static unsigned long *vmx_bitmap[VMX_BITMAP_NR];
> >
> > -#define vmx_msr_bitmap_legacy
> > (vmx_bitmap[VMX_MSR_BITMAP_LEGACY])
> > -#define vmx_msr_bitmap_longmode
> > (vmx_bitmap[VMX_MSR_BITMAP_LONGMODE])
> > -#define vmx_msr_bitmap_legacy_x2apic_apicv
> > (vmx_bitmap[VMX_MSR_BITMAP_LEGACY_X2APIC_APICV])
> > -#define vmx_msr_bitmap_longmode_x2apic_apicv
> > (vmx_bitmap[VMX_MSR_BITMAP_LONGMODE_X2APIC_APICV])
> > -#define vmx_msr_bitmap_legacy_x2apic
> > (vmx_bitmap[VMX_MSR_BITMAP_LEGACY_X2APIC])
> > -#define vmx_msr_bitmap_longmode_x2apic
> > (vmx_bitmap[VMX_MSR_BITMAP_LONGMODE_X2APIC])
> > +#define vmx_msr_bitmap_nox2apic
> > (vmx_bitmap[VMX_MSR_BITMAP_NOX2APIC])
> > +#define vmx_msr_bitmap_x2apic_apicv
> > (vmx_bitmap[VMX_MSR_BITMAP_X2APIC_APICV])
> > +#define vmx_msr_bitmap_x2apic
> > (vmx_bitmap[VMX_MSR_BITMAP_X2APIC])
> > #define vmx_vmread_bitmap
> > (vmx_bitmap[VMX_VMREAD_BITMAP])
> > #define vmx_vmwrite_bitmap
> > (vmx_bitmap[VMX_VMWRITE_BITMAP])
> >
> > @@ -2203,8 +2197,7 @@ static void vmx_save_host_state(struct kvm_vcpu
> > *vcpu)
> >
> > #ifdef CONFIG_X86_64
> > rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
> > - if (is_long_mode(&vmx->vcpu))
> > - wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
> > + wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
> > #endif
> > if (boot_cpu_has(X86_FEATURE_MPX))
> > rdmsrl(MSR_IA32_BNDCFGS, vmx->host_state.msr_host_bndcfgs);
> > @@ -2222,8 +2215,7 @@ static void __vmx_load_host_state(struct vcpu_vmx
> > *vmx)
> > ++vmx->vcpu.stat.host_state_reload;
> > vmx->host_state.loaded = 0;
> > #ifdef CONFIG_X86_64
> > - if (is_long_mode(&vmx->vcpu))
> > - rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
> > + rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
> > #endif
> > if (vmx->host_state.gs_ldt_reload_needed) {
> > kvm_load_ldt(vmx->host_state.ldt_sel);
> > @@ -2635,21 +2627,12 @@ static void vmx_set_msr_bitmap(struct kvm_vcpu
> > *vcpu)
> > (vmcs_read32(SECONDARY_VM_EXEC_CONTROL) &
> > SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) {
> > if (enable_apicv && kvm_vcpu_apicv_active(vcpu)) {
> > - if (is_long_mode(vcpu))
> > - msr_bitmap =
> > vmx_msr_bitmap_longmode_x2apic_apicv;
> > - else
> > - msr_bitmap =
> > vmx_msr_bitmap_legacy_x2apic_apicv;
> > + msr_bitmap = vmx_msr_bitmap_x2apic_apicv;
> > } else {
> > - if (is_long_mode(vcpu))
> > - msr_bitmap =
> > vmx_msr_bitmap_longmode_x2apic;
> > - else
> > - msr_bitmap = vmx_msr_bitmap_legacy_x2apic;
> > + msr_bitmap = vmx_msr_bitmap_x2apic;
> > }
> > } else {
> > - if (is_long_mode(vcpu))
> > - msr_bitmap = vmx_msr_bitmap_longmode;
> > - else
> > - msr_bitmap = vmx_msr_bitmap_legacy;
> > + msr_bitmap = vmx_msr_bitmap_nox2apic;
> > }
> >
> > vmcs_write64(MSR_BITMAP, __pa(msr_bitmap));
> > @@ -5211,22 +5194,24 @@ static void
> > nested_vmx_disable_intercept_for_msr(unsigned long *msr_bitmap_l1,
> > }
> > }
> >
> > -static void vmx_disable_intercept_for_msr(u32 msr, bool longmode_only)
> > +static void vmx_disable_intercept_for_msr(u32 msr)
> > {
> > - if (!longmode_only)
> > - __vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy,
> > - msr, MSR_TYPE_R |
> > MSR_TYPE_W);
> > - __vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode,
> > - msr, MSR_TYPE_R |
> > MSR_TYPE_W);
> > + __vmx_disable_intercept_for_msr(vmx_msr_bitmap_nox2apic,
> > + msr, MSR_TYPE_R | MSR_TYPE_W);
> > + __vmx_disable_intercept_for_msr(vmx_msr_bitmap_x2apic,
> > + msr, MSR_TYPE_R | MSR_TYPE_W);
> > + __vmx_disable_intercept_for_msr(vmx_msr_bitmap_x2apic_apicv,
> > + msr, MSR_TYPE_R | MSR_TYPE_W);
> > }
> >
> > -static void vmx_enable_intercept_for_msr(u32 msr, bool longmode_only)
> > +static void vmx_enable_intercept_for_msr(u32 msr)
> > {
> > - if (!longmode_only)
> > - __vmx_enable_intercept_for_msr(vmx_msr_bitmap_legacy,
> > - msr, MSR_TYPE_R |
> > MSR_TYPE_W);
> > - __vmx_enable_intercept_for_msr(vmx_msr_bitmap_longmode,
> > - msr, MSR_TYPE_R |
> > MSR_TYPE_W);
> > + __vmx_enable_intercept_for_msr(vmx_msr_bitmap_nox2apic,
> > + msr, MSR_TYPE_R | MSR_TYPE_W);
> > + __vmx_enable_intercept_for_msr(vmx_msr_bitmap_x2apic,
> > + msr, MSR_TYPE_R | MSR_TYPE_W);
> > + __vmx_enable_intercept_for_msr(vmx_msr_bitmap_x2apic_apicv,
> > + msr, MSR_TYPE_R | MSR_TYPE_W);
> > }
> >
> > static void pt_disable_intercept_for_msr(bool flag)
> > @@ -5235,36 +5220,29 @@ static void pt_disable_intercept_for_msr(bool flag)
> > unsigned int addr_num = kvm_get_pt_addr_cnt();
> >
> > if (flag) {
> > - vmx_disable_intercept_for_msr(MSR_IA32_RTIT_STATUS, false);
> > - vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_BASE,
> > false);
> > - vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_MASK,
> > false);
> > - vmx_disable_intercept_for_msr(MSR_IA32_RTIT_CR3_MATCH,
> > false);
> > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_STATUS);
> > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_BASE);
> > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_MASK);
> > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_CR3_MATCH);
> > for (i = 0; i < addr_num; i++)
> > - vmx_disable_intercept_for_msr(MSR_IA32_RTIT_ADDR0_A
> > + i,
> > -
> > false);
> > + vmx_disable_intercept_for_msr(MSR_IA32_RTIT_ADDR0_A
> > + i);
> > } else {
> > - vmx_enable_intercept_for_msr(MSR_IA32_RTIT_STATUS, false);
> > - vmx_enable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_BASE,
> > false);
> > - vmx_enable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_MASK,
> > false);
> > - vmx_enable_intercept_for_msr(MSR_IA32_RTIT_CR3_MATCH,
> > false);
> > + vmx_enable_intercept_for_msr(MSR_IA32_RTIT_STATUS);
> > + vmx_enable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_BASE);
> > + vmx_enable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_MASK);
> > + vmx_enable_intercept_for_msr(MSR_IA32_RTIT_CR3_MATCH);
> > for (i = 0; i < addr_num; i++)
> > - vmx_enable_intercept_for_msr(MSR_IA32_RTIT_ADDR0_A
> > + i,
> > -
> > false);
> > + vmx_enable_intercept_for_msr(MSR_IA32_RTIT_ADDR0_A
> > + i);
> > }
> > }
> >
> > static void vmx_disable_intercept_msr_x2apic(u32 msr, int type, bool
> > apicv_only)
> > {
> > - __vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic_apicv,
> > + __vmx_disable_intercept_for_msr(vmx_msr_bitmap_x2apic_apicv,
> > msr, type);
> > -
> > __vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic_apicv,
> > - msr, type);
> > - if (!apicv_only) {
> > -
> > __vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic,
> > - msr, type);
> > -
> > __vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic,
> > + if (!apicv_only)
> > + __vmx_disable_intercept_for_msr(vmx_msr_bitmap_x2apic,
> > msr, type);
> > - }
> > }
> >
> > static bool vmx_get_enable_apicv(struct kvm_vcpu *vcpu)
> > @@ -5733,7 +5711,7 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
> > vmcs_write64(VMWRITE_BITMAP, __pa(vmx_vmwrite_bitmap));
> > }
> > if (cpu_has_vmx_msr_bitmap())
> > - vmcs_write64(MSR_BITMAP, __pa(vmx_msr_bitmap_legacy));
> > + vmcs_write64(MSR_BITMAP, __pa(vmx_msr_bitmap_nox2apic));
> >
> > vmcs_write64(VMCS_LINK_POINTER, -1ull); /* 22.3.1.5 */
> >
> > @@ -7047,8 +7025,9 @@ static __init int hardware_setup(void)
> > memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);
> > memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);
> >
> > - memset(vmx_msr_bitmap_legacy, 0xff, PAGE_SIZE);
> > - memset(vmx_msr_bitmap_longmode, 0xff, PAGE_SIZE);
> > + memset(vmx_msr_bitmap_nox2apic, 0xff, PAGE_SIZE);
> > + memset(vmx_msr_bitmap_x2apic, 0xff, PAGE_SIZE);
> > + memset(vmx_msr_bitmap_x2apic_apicv, 0xff, PAGE_SIZE);
> >
> > if (setup_vmcs_config(&vmcs_config) < 0) {
> > r = -EIO;
> > @@ -7113,21 +7092,12 @@ static __init int hardware_setup(void)
> > kvm_tsc_scaling_ratio_frac_bits = 48;
> > }
> >
> > - vmx_disable_intercept_for_msr(MSR_FS_BASE, false);
> > - vmx_disable_intercept_for_msr(MSR_GS_BASE, false);
> > - vmx_disable_intercept_for_msr(MSR_KERNEL_GS_BASE, true);
> > - vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_CS, false);
> > - vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_ESP, false);
> > - vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
> > -
> > - memcpy(vmx_msr_bitmap_legacy_x2apic_apicv,
> > - vmx_msr_bitmap_legacy, PAGE_SIZE);
> > - memcpy(vmx_msr_bitmap_longmode_x2apic_apicv,
> > - vmx_msr_bitmap_longmode, PAGE_SIZE);
> > - memcpy(vmx_msr_bitmap_legacy_x2apic,
> > - vmx_msr_bitmap_legacy, PAGE_SIZE);
> > - memcpy(vmx_msr_bitmap_longmode_x2apic,
> > - vmx_msr_bitmap_longmode, PAGE_SIZE);
> > + vmx_disable_intercept_for_msr(MSR_FS_BASE);
> > + vmx_disable_intercept_for_msr(MSR_GS_BASE);
> > + vmx_disable_intercept_for_msr(MSR_KERNEL_GS_BASE);
> > + vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_CS);
> > + vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_ESP);
> > + vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP);
> >
> > set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */
> >
> > --
> > 1.8.3.1
> >
>

Next message: Rasmus Villemoes: "[PATCH] scsi: fnic: use kzalloc in fnic_fcoe_process_vlan_resp"
Previous message: Kees Cook: "Re: [PATCH RFC 3/4] x86/pti: don't mark the user PGD with _PAGE_NX."
In reply to: Jim Mattson: "Re: [PATCH] KVM: VMX: use same MSR bitmaps for 32-/64-bit modes, fix MSR bitmaps for processor tracing"
Next in thread: Paolo Bonzini: "Re: [PATCH] KVM: VMX: use same MSR bitmaps for 32-/64-bit modes, fix MSR bitmaps for processor tracing"
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