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SubjectRe: [PATCH] KVM: SVM: Use a separate vmcb for the nested L2 guest
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On 9/18/20 11:16 AM, Babu Moger wrote:
> Cathy,
> Thanks for the patches. It cleans up the code nicely.
> But there are some issues with the patch. I was able to bring the L1 guest
> with your patch. But when I tried to load L2 guest it crashed. I am
> thinking It is mostly due to save/restore part of vmcb. Few comments below.
>
>> -----Original Message-----
>> From: Cathy Avery <cavery@redhat.com>
>> Sent: Thursday, September 17, 2020 2:23 PM
>> To: linux-kernel@vger.kernel.org; kvm@vger.kernel.org; pbonzini@redhat.com
>> Cc: vkuznets@redhat.com; Huang2, Wei <Wei.Huang2@amd.com>
>> Subject: [PATCH] KVM: SVM: Use a separate vmcb for the nested L2 guest
>>
>> svm->vmcb will now point to either a separate vmcb L1 ( not nested ) or L2 vmcb
>> ( nested ).
>>
>> Issues:
>>
>> 1) There is some wholesale copying of vmcb.save and vmcb.contol
>> areas which will need to be refined.
>>
>> 2) There is a workaround in nested_svm_vmexit() where
>>
>> if (svm->vmcb01->control.asid == 0)
>> svm->vmcb01->control.asid = svm->nested.vmcb02->control.asid;
>>
>> This was done as a result of the kvm selftest 'state_test'. In that
>> test svm_set_nested_state() is called before svm_vcpu_run().
>> The asid is assigned by svm_vcpu_run -> pre_svm_run for the current
>> vmcb which is now vmcb02 as we are in nested mode subsequently
>> vmcb01.control.asid is never set as it should be.
>>
>> Tested:
>> kvm-unit-tests
>> kvm self tests
>>
>> Signed-off-by: Cathy Avery <cavery@redhat.com>
>> ---
>> arch/x86/kvm/svm/nested.c | 116 ++++++++++++++++++--------------------
>> arch/x86/kvm/svm/svm.c | 41 +++++++-------
>> arch/x86/kvm/svm/svm.h | 10 ++--
>> 3 files changed, 81 insertions(+), 86 deletions(-)
>>
>> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index
>> e90bc436f584..0a06e62010d8 100644
>> --- a/arch/x86/kvm/svm/nested.c
>> +++ b/arch/x86/kvm/svm/nested.c
>> @@ -75,12 +75,12 @@ static unsigned long nested_svm_get_tdp_cr3(struct
>> kvm_vcpu *vcpu) static void nested_svm_init_mmu_context(struct kvm_vcpu
>> *vcpu) {
>> struct vcpu_svm *svm = to_svm(vcpu);
>> - struct vmcb *hsave = svm->nested.hsave;
>>
>> WARN_ON(mmu_is_nested(vcpu));
>>
>> vcpu->arch.mmu = &vcpu->arch.guest_mmu;
>> - kvm_init_shadow_npt_mmu(vcpu, X86_CR0_PG, hsave->save.cr4,
>> hsave->save.efer,
>> + kvm_init_shadow_npt_mmu(vcpu, X86_CR0_PG, svm->vmcb01-
>>> save.cr4,
>> + svm->vmcb01->save.efer,
>> svm->nested.ctl.nested_cr3);
>> vcpu->arch.mmu->get_guest_pgd = nested_svm_get_tdp_cr3;
>> vcpu->arch.mmu->get_pdptr = nested_svm_get_tdp_pdptr;
>> @@ -105,7 +105,7 @@ void recalc_intercepts(struct vcpu_svm *svm)
>> return;
>>
>> c = &svm->vmcb->control;
>> - h = &svm->nested.hsave->control;
>> + h = &svm->vmcb01->control;
>> g = &svm->nested.ctl;
>>
>> svm->nested.host_intercept_exceptions = h->intercept_exceptions;
>> @@ -403,7 +403,7 @@ static void nested_prepare_vmcb_control(struct
>> vcpu_svm *svm)
>>
>> svm->vmcb->control.int_ctl =
>> (svm->nested.ctl.int_ctl & ~mask) |
>> - (svm->nested.hsave->control.int_ctl & mask);
>> + (svm->vmcb01->control.int_ctl & mask);
>>
>> svm->vmcb->control.virt_ext = svm->nested.ctl.virt_ext;
>> svm->vmcb->control.int_vector = svm->nested.ctl.int_vector;
>> @@ -432,6 +432,12 @@ int enter_svm_guest_mode(struct vcpu_svm *svm, u64
>> vmcb_gpa,
>> int ret;
>>
>> svm->nested.vmcb = vmcb_gpa;
>> +
>> + WARN_ON(svm->vmcb == svm->nested.vmcb02);
>> +
>> + svm->nested.vmcb02->control = svm->vmcb01->control;
>> + svm->vmcb = svm->nested.vmcb02;
>> + svm->vmcb_pa = svm->nested.vmcb02_pa;
>> load_nested_vmcb_control(svm, &nested_vmcb->control);
>> nested_prepare_vmcb_save(svm, nested_vmcb);
>> nested_prepare_vmcb_control(svm);
>> @@ -450,8 +456,6 @@ int nested_svm_vmrun(struct vcpu_svm *svm) {
>> int ret;
>> struct vmcb *nested_vmcb;
>> - struct vmcb *hsave = svm->nested.hsave;
>> - struct vmcb *vmcb = svm->vmcb;
>> struct kvm_host_map map;
>> u64 vmcb_gpa;
>>
>> @@ -496,29 +500,17 @@ int nested_svm_vmrun(struct vcpu_svm *svm)
>> kvm_clear_exception_queue(&svm->vcpu);
>> kvm_clear_interrupt_queue(&svm->vcpu);
>>
>> - /*
>> - * Save the old vmcb, so we don't need to pick what we save, but can
>> - * restore everything when a VMEXIT occurs
>> - */
>> - hsave->save.es = vmcb->save.es;
>> - hsave->save.cs = vmcb->save.cs;
>> - hsave->save.ss = vmcb->save.ss;
>> - hsave->save.ds = vmcb->save.ds;
>> - hsave->save.gdtr = vmcb->save.gdtr;
>> - hsave->save.idtr = vmcb->save.idtr;
>> - hsave->save.efer = svm->vcpu.arch.efer;
>> - hsave->save.cr0 = kvm_read_cr0(&svm->vcpu);
>> - hsave->save.cr4 = svm->vcpu.arch.cr4;
>> - hsave->save.rflags = kvm_get_rflags(&svm->vcpu);
>> - hsave->save.rip = kvm_rip_read(&svm->vcpu);
>> - hsave->save.rsp = vmcb->save.rsp;
>> - hsave->save.rax = vmcb->save.rax;
>> - if (npt_enabled)
>> - hsave->save.cr3 = vmcb->save.cr3;
>> - else
>> - hsave->save.cr3 = kvm_read_cr3(&svm->vcpu);
>> -
>> - copy_vmcb_control_area(&hsave->control, &vmcb->control);
> You may have to carefully check the above cleanup.
Thanks I'll check it out. I did not see a crash when running the tests. 
Could you send me more information about your test and test setup, stack
trace, etc.
>
>> +
>> + /* Update vmcb0. We will restore everything when a VMEXIT occurs */
>> +
>> + svm->vmcb01->save.efer = svm->vcpu.arch.efer;
>> + svm->vmcb01->save.cr0 = kvm_read_cr0(&svm->vcpu);
>> + svm->vmcb01->save.cr4 = svm->vcpu.arch.cr4;
>> + svm->vmcb01->save.rflags = kvm_get_rflags(&svm->vcpu);
>> + svm->vmcb01->save.rip = kvm_rip_read(&svm->vcpu);
>> +
>> + if (!npt_enabled)
>> + svm->vmcb01->save.cr3 = kvm_read_cr3(&svm->vcpu);
>>
>> svm->nested.nested_run_pending = 1;
>>
>> @@ -564,7 +556,6 @@ int nested_svm_vmexit(struct vcpu_svm *svm) {
>> int rc;
>> struct vmcb *nested_vmcb;
>> - struct vmcb *hsave = svm->nested.hsave;
>> struct vmcb *vmcb = svm->vmcb;
>> struct kvm_host_map map;
>>
>> @@ -628,8 +619,11 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
>> nested_vmcb->control.pause_filter_thresh =
>> svm->vmcb->control.pause_filter_thresh;
>>
>> - /* Restore the original control entries */
>> - copy_vmcb_control_area(&vmcb->control, &hsave->control);
>> + if (svm->vmcb01->control.asid == 0)
>> + svm->vmcb01->control.asid = svm->nested.vmcb02-
>>> control.asid;
>> +
>> + svm->vmcb = svm->vmcb01;
>> + svm->vmcb_pa = svm->nested.vmcb01_pa;
>>
>> /* On vmexit the GIF is set to false */
>> svm_set_gif(svm, false);
>> @@ -640,19 +634,13 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
>> svm->nested.ctl.nested_cr3 = 0;
>>
>> /* Restore selected save entries */
>> - svm->vmcb->save.es = hsave->save.es;
>> - svm->vmcb->save.cs = hsave->save.cs;
>> - svm->vmcb->save.ss = hsave->save.ss;
>> - svm->vmcb->save.ds = hsave->save.ds;
>> - svm->vmcb->save.gdtr = hsave->save.gdtr;
>> - svm->vmcb->save.idtr = hsave->save.idtr;
>> - kvm_set_rflags(&svm->vcpu, hsave->save.rflags);
>> - svm_set_efer(&svm->vcpu, hsave->save.efer);
>> - svm_set_cr0(&svm->vcpu, hsave->save.cr0 | X86_CR0_PE);
>> - svm_set_cr4(&svm->vcpu, hsave->save.cr4);
>> - kvm_rax_write(&svm->vcpu, hsave->save.rax);
>> - kvm_rsp_write(&svm->vcpu, hsave->save.rsp);
>> - kvm_rip_write(&svm->vcpu, hsave->save.rip);
>> + kvm_set_rflags(&svm->vcpu, svm->vmcb->save.rflags);
>> + svm_set_efer(&svm->vcpu, svm->vmcb->save.efer);
>> + svm_set_cr0(&svm->vcpu, svm->vmcb->save.cr0 | X86_CR0_PE);
>> + svm_set_cr4(&svm->vcpu, svm->vmcb->save.cr4);
>> + kvm_rax_write(&svm->vcpu, svm->vmcb->save.rax);
>> + kvm_rsp_write(&svm->vcpu, svm->vmcb->save.rsp);
>> + kvm_rip_write(&svm->vcpu, svm->vmcb->save.rip);
>> svm->vmcb->save.dr7 = 0;
>> svm->vmcb->save.cpl = 0;
>> svm->vmcb->control.exit_int_info = 0;
>> @@ -670,12 +658,12 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
>>
>> nested_svm_uninit_mmu_context(&svm->vcpu);
>>
>> - rc = nested_svm_load_cr3(&svm->vcpu, hsave->save.cr3, false);
>> + rc = nested_svm_load_cr3(&svm->vcpu, svm->vmcb->save.cr3, false);
>> if (rc)
>> return 1;
>>
>> - if (npt_enabled)
>> - svm->vmcb->save.cr3 = hsave->save.cr3;
>> + if (!npt_enabled)
>> + svm->vmcb01->save.cr3 = kvm_read_cr3(&svm->vcpu);
>>
>> /*
>> * Drop what we picked up for L2 via svm_complete_interrupts() so it
>> @@ -694,12 +682,10 @@ int nested_svm_vmexit(struct vcpu_svm *svm) void
>> svm_leave_nested(struct vcpu_svm *svm) {
>> if (is_guest_mode(&svm->vcpu)) {
>> - struct vmcb *hsave = svm->nested.hsave;
>> - struct vmcb *vmcb = svm->vmcb;
>> -
>> svm->nested.nested_run_pending = 0;
>> leave_guest_mode(&svm->vcpu);
>> - copy_vmcb_control_area(&vmcb->control, &hsave->control);
>> + svm->vmcb = svm->vmcb01;
>> + svm->vmcb_pa = svm->nested.vmcb01_pa;
>> nested_svm_uninit_mmu_context(&svm->vcpu);
>> }
>> }
>> @@ -1046,10 +1032,9 @@ static int svm_get_nested_state(struct kvm_vcpu
>> *vcpu,
>> if (copy_to_user(&user_vmcb->control, &svm->nested.ctl,
>> sizeof(user_vmcb->control)))
>> return -EFAULT;
>> - if (copy_to_user(&user_vmcb->save, &svm->nested.hsave->save,
>> + if (copy_to_user(&user_vmcb->save, &svm->vmcb01->save,
>> sizeof(user_vmcb->save)))
>> return -EFAULT;
>> -
>> out:
>> return kvm_state.size;
>> }
>> @@ -1059,7 +1044,6 @@ static int svm_set_nested_state(struct kvm_vcpu
>> *vcpu,
>> struct kvm_nested_state *kvm_state) {
>> struct vcpu_svm *svm = to_svm(vcpu);
>> - struct vmcb *hsave = svm->nested.hsave;
>> struct vmcb __user *user_vmcb = (struct vmcb __user *)
>> &user_kvm_nested_state->data.svm[0];
>> struct vmcb_control_area ctl;
>> @@ -1121,16 +1105,24 @@ static int svm_set_nested_state(struct kvm_vcpu
>> *vcpu,
>> if (!(save.cr0 & X86_CR0_PG))
>> return -EINVAL;
>>
>> + svm->nested.vmcb02->control = svm->vmcb01->control;
>> + svm->nested.vmcb02->save = svm->vmcb01->save;
>> + svm->vmcb01->save = save;
>> +
>> + WARN_ON(svm->vmcb == svm->nested.vmcb02);
>> +
>> + svm->nested.vmcb = kvm_state->hdr.svm.vmcb_pa;
>> +
>> + svm->vmcb = svm->nested.vmcb02;
>> + svm->vmcb_pa = svm->nested.vmcb02_pa;
>> +
>> /*
>> - * All checks done, we can enter guest mode. L1 control fields
>> - * come from the nested save state. Guest state is already
>> - * in the registers, the save area of the nested state instead
>> - * contains saved L1 state.
>> + * All checks done, we can enter guest mode. L2 control fields will
>> + * be the result of a combination of L1 and userspace indicated
>> + * L12.control. The save area of L1 vmcb now contains the userspace
>> + * indicated L1.save.
>> */
>> - copy_vmcb_control_area(&hsave->control, &svm->vmcb->control);
>> - hsave->save = save;
>>
>> - svm->nested.vmcb = kvm_state->hdr.svm.vmcb_pa;
>> load_nested_vmcb_control(svm, &ctl);
>> nested_prepare_vmcb_control(svm);
>>
>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index
>> 5764b87379cf..d8022f989ffb 100644
>> --- a/arch/x86/kvm/svm/svm.c
>> +++ b/arch/x86/kvm/svm/svm.c
>> @@ -971,8 +971,8 @@ static u64 svm_write_l1_tsc_offset(struct kvm_vcpu
>> *vcpu, u64 offset)
>> 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;
>> + svm->vmcb01->control.tsc_offset;
>> + svm->vmcb01->control.tsc_offset = offset;
>> }
>>
>> trace_kvm_write_tsc_offset(vcpu->vcpu_id,
>> @@ -1171,9 +1171,9 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu,
>> bool init_event) static int svm_create_vcpu(struct kvm_vcpu *vcpu) {
>> struct vcpu_svm *svm;
>> - struct page *page;
>> + struct page *vmcb01_page;
>> + struct page *vmcb02_page;
>> struct page *msrpm_pages;
>> - struct page *hsave_page;
>> struct page *nested_msrpm_pages;
>> int err;
>>
>> @@ -1181,8 +1181,8 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
>> svm = to_svm(vcpu);
>>
>> err = -ENOMEM;
>> - page = alloc_page(GFP_KERNEL_ACCOUNT);
>> - if (!page)
>> + vmcb01_page = alloc_page(GFP_KERNEL_ACCOUNT);
>> + if (!vmcb01_page)
>> goto out;
>>
>> msrpm_pages = alloc_pages(GFP_KERNEL_ACCOUNT,
>> MSRPM_ALLOC_ORDER); @@ -1193,8 +1193,8 @@ static int
>> svm_create_vcpu(struct kvm_vcpu *vcpu)
>> if (!nested_msrpm_pages)
>> goto free_page2;
>>
>> - hsave_page = alloc_page(GFP_KERNEL_ACCOUNT);
>> - if (!hsave_page)
>> + vmcb02_page = alloc_page(GFP_KERNEL_ACCOUNT);
>> + if (!vmcb02_page)
>> goto free_page3;
>>
>> err = avic_init_vcpu(svm);
>> @@ -1207,8 +1207,9 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
>> if (irqchip_in_kernel(vcpu->kvm) && kvm_apicv_activated(vcpu->kvm))
>> svm->avic_is_running = true;
>>
>> - svm->nested.hsave = page_address(hsave_page);
>> - clear_page(svm->nested.hsave);
>> + svm->nested.vmcb02 = page_address(vmcb02_page);
>> + clear_page(svm->nested.vmcb02);
>> + svm->nested.vmcb02_pa = __sme_set(page_to_pfn(vmcb02_page) <<
>> +PAGE_SHIFT);
>>
>> svm->msrpm = page_address(msrpm_pages);
>> svm_vcpu_init_msrpm(svm->msrpm);
>> @@ -1216,9 +1217,11 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
>> svm->nested.msrpm = page_address(nested_msrpm_pages);
>> svm_vcpu_init_msrpm(svm->nested.msrpm);
>>
>> - svm->vmcb = page_address(page);
>> + svm->vmcb = svm->vmcb01 = page_address(vmcb01_page);
>> clear_page(svm->vmcb);
>> - svm->vmcb_pa = __sme_set(page_to_pfn(page) << PAGE_SHIFT);
>> + svm->vmcb_pa = __sme_set(page_to_pfn(vmcb01_page) <<
>> PAGE_SHIFT);
>> + svm->nested.vmcb01_pa = svm->vmcb_pa;
>> +
>> svm->asid_generation = 0;
>> init_vmcb(svm);
>>
>> @@ -1228,13 +1231,13 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
>> return 0;
>>
>> free_page4:
>> - __free_page(hsave_page);
>> + __free_page(vmcb02_page);
>> free_page3:
>> __free_pages(nested_msrpm_pages, MSRPM_ALLOC_ORDER);
>> free_page2:
>> __free_pages(msrpm_pages, MSRPM_ALLOC_ORDER);
>> free_page1:
>> - __free_page(page);
>> + __free_page(vmcb01_page);
>> out:
>> return err;
>> }
>> @@ -1256,11 +1259,11 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
>> * svm_vcpu_load(). So, ensure that no logical CPU has this
>> * vmcb page recorded as its current vmcb.
>> */
>> - svm_clear_current_vmcb(svm->vmcb);
>>
>> - __free_page(pfn_to_page(__sme_clr(svm->vmcb_pa) >> PAGE_SHIFT));
>> + svm_clear_current_vmcb(svm->vmcb);
>> + __free_page(pfn_to_page(__sme_clr(svm->nested.vmcb01_pa) >>
>> PAGE_SHIFT));
>> + __free_page(pfn_to_page(__sme_clr(svm->nested.vmcb02_pa) >>
>> +PAGE_SHIFT));
>> __free_pages(virt_to_page(svm->msrpm), MSRPM_ALLOC_ORDER);
>> - __free_page(virt_to_page(svm->nested.hsave));
>> __free_pages(virt_to_page(svm->nested.msrpm),
>> MSRPM_ALLOC_ORDER); }
>>
>> @@ -1393,7 +1396,7 @@ static void svm_clear_vintr(struct vcpu_svm *svm)
>> /* Drop int_ctl fields related to VINTR injection. */
>> svm->vmcb->control.int_ctl &= mask;
>> if (is_guest_mode(&svm->vcpu)) {
>> - svm->nested.hsave->control.int_ctl &= mask;
>> + svm->vmcb01->control.int_ctl &= mask;
>>
>> WARN_ON((svm->vmcb->control.int_ctl & V_TPR_MASK) !=
>> (svm->nested.ctl.int_ctl & V_TPR_MASK)); @@ -3127,7
>> +3130,7 @@ bool svm_interrupt_blocked(struct kvm_vcpu *vcpu)
>> if (is_guest_mode(vcpu)) {
>> /* As long as interrupts are being delivered... */
>> if ((svm->nested.ctl.int_ctl & V_INTR_MASKING_MASK)
>> - ? !(svm->nested.hsave->save.rflags & X86_EFLAGS_IF)
>> + ? !(svm->vmcb01->save.rflags & X86_EFLAGS_IF)
>> : !(kvm_get_rflags(vcpu) & X86_EFLAGS_IF))
>> return true;
>>
>> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index
>> a798e1731709..e908b83bfa69 100644
>> --- a/arch/x86/kvm/svm/svm.h
>> +++ b/arch/x86/kvm/svm/svm.h
>> @@ -82,7 +82,9 @@ struct kvm_svm {
>> struct kvm_vcpu;
>>
>> struct svm_nested_state {
>> - struct vmcb *hsave;
>> + struct vmcb *vmcb02;
>> + unsigned long vmcb01_pa;
>> + unsigned long vmcb02_pa;
>> u64 hsave_msr;
>> u64 vm_cr_msr;
>> u64 vmcb;
>> @@ -102,6 +104,7 @@ struct svm_nested_state { struct vcpu_svm {
>> struct kvm_vcpu vcpu;
>> struct vmcb *vmcb;
>> + struct vmcb *vmcb01;
>> unsigned long vmcb_pa;
>> struct svm_cpu_data *svm_data;
>> uint64_t asid_generation;
>> @@ -208,10 +211,7 @@ static inline struct vcpu_svm *to_svm(struct kvm_vcpu
>> *vcpu)
>>
>> static inline struct vmcb *get_host_vmcb(struct vcpu_svm *svm) {
>> - if (is_guest_mode(&svm->vcpu))
>> - return svm->nested.hsave;
>> - else
>> - return svm->vmcb;
>> + return svm->vmcb01;
> Shouldn't it return svm->vmcb? That is what your commit message says.
I believe this is correct. The function is designed to return the host
vmcb which will always be vmcb01.
>
>> }
>>
>> static inline void set_cr_intercept(struct vcpu_svm *svm, int bit)
>> --
>> 2.20.1


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