Re: [PATCH 1/2] X86/KVM: Properly update 'tsc_offset' to represent the running guest
On Fri, 2018-04-13 at 17:35 +0200, Paolo Bonzini wrote:
> On 13/04/2018 14:40, Raslan, KarimAllah wrote:
> >
> > >
> > >
> > > static void update_ia32_tsc_adjust_msr(struct kvm_vcpu *vcpu, s64 offset)
> > > {
> > > - u64 curr_offset = vcpu->arch.tsc_offset;
> > > + u64 curr_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
> > I might be missing something but is this really strictly needed or is
> > it really a bug?
> >
> > I can see update_ia32_tsc_adjust_msr called from kvm_write_tsc only
> > which is called from a) vmx_set_msr or b) kvm_arch_vcpu_postcreate.
> > The adjust_msr would only be called if !host_initiated. So only
> > vmx_set_msr which is coming from an L1 write (or a restore but that
> > would not be !host_initiated). So the only that tsc_adjust is called is
> > !is_guest_mode.
>
> It can also be called from guest mode if the MSR bitmap says there's no
> L1 vmexit for that MSR; that's what the testcases do.
Apparently I will never wrap my head around this nested stuff :D
>
> Paolo
>
> >
> > >
> > > vcpu->arch.ia32_tsc_adjust_msr += offset - curr_offset;
>
>
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Re: [PATCH 1/2] X86/KVM: Properly update 'tsc_offset' to represent the running guest
On Fri, 2018-04-13 at 18:04 +0200, Paolo Bonzini wrote: > On 13/04/2018 18:02, Jim Mattson wrote: > > > > On Fri, Apr 13, 2018 at 4:23 AM, Paolo Bonzini wrote: > > > > > > From: KarimAllah Ahmed > > > > > > Update 'tsc_offset' on vmenty/vmexit of L2 guests to ensure that it always > > > captures the TSC_OFFSET of the running guest whether it is the L1 or L2 > > > guest. > > > > > > Cc: Jim Mattson > > > Cc: Paolo Bonzini > > > Cc: Radim Krčmář > > > Cc: k...@vger.kernel.org > > > Cc: linux-kernel@vger.kernel.org > > > Suggested-by: Paolo Bonzini > > > Signed-off-by: KarimAllah Ahmed > > > [AMD changes, fix update_ia32_tsc_adjust_msr. - Paolo] > > > Signed-off-by: Paolo Bonzini > > > > > > > > @@ -11489,6 +11497,9 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, > > > bool launch) > > > if (enable_shadow_vmcs) > > > copy_shadow_to_vmcs12(vmx); > > > > > > + if (vmcs12->cpu_based_vm_exec_control & > > > CPU_BASED_USE_TSC_OFFSETING) > > > + vcpu->arch.tsc_offset += vmcs12->tsc_offset; > > > + > > > > This seems a little early, since we don't restore the L1 TSC offset on > > the nested_vmx_failValid path. > > > > Now this can be a nice one to introduce the VMX API tests. :) I'll try > to do it on Monday as punishment for not noticing the bug. In the > meanwhile, Karim, can you post a fixed fixed version? done > > Paolo > Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
Re: [PATCH 1/2] X86/KVM: Properly update 'tsc_offset' to represent the running guest
On 13/04/2018 18:02, Jim Mattson wrote: > On Fri, Apr 13, 2018 at 4:23 AM, Paolo Bonzini wrote: >> From: KarimAllah Ahmed >> >> Update 'tsc_offset' on vmenty/vmexit of L2 guests to ensure that it always >> captures the TSC_OFFSET of the running guest whether it is the L1 or L2 >> guest. >> >> Cc: Jim Mattson >> Cc: Paolo Bonzini >> Cc: Radim Krčmář >> Cc: k...@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Suggested-by: Paolo Bonzini >> Signed-off-by: KarimAllah Ahmed >> [AMD changes, fix update_ia32_tsc_adjust_msr. - Paolo] >> Signed-off-by: Paolo Bonzini > >> @@ -11489,6 +11497,9 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, >> bool launch) >> if (enable_shadow_vmcs) >> copy_shadow_to_vmcs12(vmx); >> >> + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING) >> + vcpu->arch.tsc_offset += vmcs12->tsc_offset; >> + > > This seems a little early, since we don't restore the L1 TSC offset on > the nested_vmx_failValid path. > Now this can be a nice one to introduce the VMX API tests. :) I'll try to do it on Monday as punishment for not noticing the bug. In the meanwhile, Karim, can you post a fixed fixed version? Paolo
Re: [PATCH 1/2] X86/KVM: Properly update 'tsc_offset' to represent the running guest
On Fri, Apr 13, 2018 at 4:23 AM, Paolo Bonzini wrote: > From: KarimAllah Ahmed > > Update 'tsc_offset' on vmenty/vmexit of L2 guests to ensure that it always > captures the TSC_OFFSET of the running guest whether it is the L1 or L2 > guest. > > Cc: Jim Mattson > Cc: Paolo Bonzini > Cc: Radim Krčmář > Cc: k...@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Suggested-by: Paolo Bonzini > Signed-off-by: KarimAllah Ahmed > [AMD changes, fix update_ia32_tsc_adjust_msr. - Paolo] > Signed-off-by: Paolo Bonzini > @@ -11489,6 +11497,9 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool > launch) > if (enable_shadow_vmcs) > copy_shadow_to_vmcs12(vmx); > > + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING) > + vcpu->arch.tsc_offset += vmcs12->tsc_offset; > + This seems a little early, since we don't restore the L1 TSC offset on the nested_vmx_failValid path.
Re: [PATCH 1/2] X86/KVM: Properly update 'tsc_offset' to represent the running guest
On 13/04/2018 14:40, Raslan, KarimAllah wrote:
>>
>> static void update_ia32_tsc_adjust_msr(struct kvm_vcpu *vcpu, s64 offset)
>> {
>> -u64 curr_offset = vcpu->arch.tsc_offset;
>> +u64 curr_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
> I might be missing something but is this really strictly needed or is
> it really a bug?
>
> I can see update_ia32_tsc_adjust_msr called from kvm_write_tsc only
> which is called from a) vmx_set_msr or b) kvm_arch_vcpu_postcreate.
> The adjust_msr would only be called if !host_initiated. So only
> vmx_set_msr which is coming from an L1 write (or a restore but that
> would not be !host_initiated). So the only that tsc_adjust is called is
> !is_guest_mode.
It can also be called from guest mode if the MSR bitmap says there's no
L1 vmexit for that MSR; that's what the testcases do.
Paolo
>> vcpu->arch.ia32_tsc_adjust_msr += offset - curr_offset;
Re: [PATCH 1/2] X86/KVM: Properly update 'tsc_offset' to represent the running guest
On Fri, 2018-04-13 at 13:23 +0200, Paolo Bonzini wrote:
> From: KarimAllah Ahmed
>
> Update 'tsc_offset' on vmenty/vmexit of L2 guests to ensure that it always
> captures the TSC_OFFSET of the running guest whether it is the L1 or L2
> guest.
>
> Cc: Jim Mattson
> Cc: Paolo Bonzini
> Cc: Radim Krčmář
> Cc: k...@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Suggested-by: Paolo Bonzini
> Signed-off-by: KarimAllah Ahmed
> [AMD changes, fix update_ia32_tsc_adjust_msr. - Paolo]
> Signed-off-by: Paolo Bonzini
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/svm.c | 17 -
> arch/x86/kvm/vmx.c | 25 -
> arch/x86/kvm/x86.c | 6 --
> 4 files changed, 41 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 949c977bc4c9..c25775fad4ed 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1013,6 +1013,7 @@ struct kvm_x86_ops {
>
> bool (*has_wbinvd_exit)(void);
>
> + u64 (*read_l1_tsc_offset)(struct kvm_vcpu *vcpu);
> void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
>
> void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index b3ebc8ad6891..ea7c6d29aca5 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
Thank you for adding the AMD bits, I did not have a machine to test the
AMD bits on so I left it untouched :)
> @@ -1424,12 +1424,23 @@ static void init_sys_seg(struct vmcb_seg *seg,
> uint32_t type)
> seg->base = 0;
> }
>
> +static u64 svm_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
> +{
> + struct vcpu_svm *svm = to_svm(vcpu);
> +
> + if (is_guest_mode(vcpu))
> + return svm->nested.hsave->control.tsc_offset;
> +
> + return vcpu->arch.tsc_offset;
> +}
> +
> static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
> u64 g_tsc_offset = 0;
>
> if (is_guest_mode(vcpu)) {
> + /* Write L1's TSC offset. */
> g_tsc_offset = svm->vmcb->control.tsc_offset -
> svm->nested.hsave->control.tsc_offset;
> svm->nested.hsave->control.tsc_offset = offset;
> @@ -3323,6 +3334,7 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
> /* Restore the original control entries */
> copy_vmcb_control_area(vmcb, hsave);
>
> + vcpu->arch.tsc_offset = svm->vmcb->control.tsc_offset;
> kvm_clear_exception_queue(&svm->vcpu);
> kvm_clear_interrupt_queue(&svm->vcpu);
>
> @@ -3483,10 +3495,12 @@ static void enter_svm_guest_mode(struct vcpu_svm
> *svm, u64 vmcb_gpa,
> /* We don't want to see VMMCALLs from a nested guest */
> clr_intercept(svm, INTERCEPT_VMMCALL);
>
> + vcpu->arch.tsc_offset += nested_vmcb->control.tsc_offset;
> + svm->vmcb->control.tsc_offset = vcpu->arch.tsc_offset;
> +
> svm->vmcb->control.virt_ext = nested_vmcb->control.virt_ext;
> svm->vmcb->control.int_vector = nested_vmcb->control.int_vector;
> svm->vmcb->control.int_state = nested_vmcb->control.int_state;
> - svm->vmcb->control.tsc_offset += nested_vmcb->control.tsc_offset;
> svm->vmcb->control.event_inj = nested_vmcb->control.event_inj;
> svm->vmcb->control.event_inj_err = nested_vmcb->control.event_inj_err;
>
> @@ -7102,6 +7116,7 @@ static int svm_unregister_enc_region(struct kvm *kvm,
>
> .has_wbinvd_exit = svm_has_wbinvd_exit,
>
> + .read_l1_tsc_offset = svm_read_l1_tsc_offset,
> .write_tsc_offset = svm_write_tsc_offset,
>
> .set_tdp_cr3 = set_tdp_cr3,
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index a13c603bdefb..6553419202ee 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2874,6 +2874,17 @@ static void setup_msrs(struct vcpu_vmx *vmx)
> vmx_update_msr_bitmap(&vmx->vcpu);
> }
>
> +static u64 vmx_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
> +{
> + struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> +
> + if (is_guest_mode(vcpu) &&
> + (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING))
> + return vcpu->arch.tsc_offset - vmcs12->tsc_offset;
> +
> + return vcpu->arch.tsc_offset;
> +}
> +
> /*
> * reads and returns guest's timestamp counter "register"
> * guest_tsc = (host_tsc * tsc multiplier) >> 48 + tsc_offset
> @@ -11175,11 +11186,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12,
> vmcs_write64(GUEST_IA32_PAT, vmx->vcpu.arch.pat);
> }
>
> - if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
> - vmcs_write64(TSC_OFFSET,
> - vcpu->arch.tsc_offset + vmcs12->tsc_offset);
> - else
> - vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
> +
