Re: [PATCH] KVM: SVM: Use a separate vmcb for the nested L2 guest
From: Cathy Avery
Date: Fri Sep 18 2020 - 11:27:31 EST
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@xxxxxxxxxx>
Sent: Thursday, September 17, 2020 2:23 PM
To: linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; pbonzini@xxxxxxxxxx
Cc: vkuznets@xxxxxxxxxx; Huang2, Wei <Wei.Huang2@xxxxxxx>
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@xxxxxxxxxx>
---
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