* [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest
@ 2020-07-08 9:36 Vitaly Kuznetsov
2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw)
To: kvm, Paolo Bonzini
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid,
linux-kernel
This is a succesor of "[PATCH] KVM: x86: drop erroneous mmu_check_root()
from fast_pgd_switch()".
Undesired triple fault gets injected to L1 guest on SVM when L2 is
launched with certain CR3 values. #TF is raised by mmu_check_root()
check in fast_pgd_switch() and the root cause is that when
kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT
enabled CR3 points to a nGPA so we can't check it with
kvm_is_visible_gfn().
Fix the issue by moving kvm_mmu_new_pgd() to the right place when switching
to nested guest and drop the unneeded mmu_check_root() check from
fast_pgd_switch().
Vitaly Kuznetsov (3):
KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu()
KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest
KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch()
arch/x86/include/asm/kvm_host.h | 7 ++++++-
arch/x86/kvm/mmu.h | 3 ++-
arch/x86/kvm/mmu/mmu.c | 36 ++++++++++++++++++++++++---------
arch/x86/kvm/svm/nested.c | 5 +++--
arch/x86/kvm/x86.c | 8 +++++---
5 files changed, 43 insertions(+), 16 deletions(-)
--
2.25.4
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu()
2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov
@ 2020-07-08 9:36 ` Vitaly Kuznetsov
2020-07-08 11:25 ` Paolo Bonzini
2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov
2020-07-08 9:36 ` [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov
2 siblings, 1 reply; 7+ messages in thread
From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw)
To: kvm, Paolo Bonzini
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid,
linux-kernel
As a preparatory change for moving kvm_mmu_new_pgd() from
nested_prepare_vmcb_save() to nested_svm_init_mmu_context() split
kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu(). This also makes
the code look more like nVMX (kvm_init_shadow_ept_mmu()).
No functional change intended.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/mmu.h | 3 ++-
arch/x86/kvm/mmu/mmu.c | 31 ++++++++++++++++++++++++-------
arch/x86/kvm/svm/nested.c | 3 ++-
3 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 444bb9c54548..94378ef1df54 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -57,7 +57,8 @@ void
reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
void kvm_init_mmu(struct kvm_vcpu *vcpu, bool reset_roots);
-void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer);
+void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
+ gpa_t nested_cr3);
void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
bool accessed_dirty, gpa_t new_eptp);
bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 76817d13c86e..167d12ab957a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4952,14 +4952,10 @@ kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only)
return role;
}
-void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer)
+static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4,
+ u32 efer, union kvm_mmu_role new_role)
{
struct kvm_mmu *context = vcpu->arch.mmu;
- union kvm_mmu_role new_role =
- kvm_calc_shadow_mmu_root_page_role(vcpu, false);
-
- if (new_role.as_u64 == context->mmu_role.as_u64)
- return;
if (!(cr0 & X86_CR0_PG))
nonpaging_init_context(vcpu, context);
@@ -4973,7 +4969,28 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer)
context->mmu_role.as_u64 = new_role.as_u64;
reset_shadow_zero_bits_mask(vcpu, context);
}
-EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
+
+static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer)
+{
+ struct kvm_mmu *context = vcpu->arch.mmu;
+ union kvm_mmu_role new_role =
+ kvm_calc_shadow_mmu_root_page_role(vcpu, false);
+
+ if (new_role.as_u64 != context->mmu_role.as_u64)
+ shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role);
+}
+
+void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
+ gpa_t nested_cr3)
+{
+ struct kvm_mmu *context = vcpu->arch.mmu;
+ union kvm_mmu_role new_role =
+ kvm_calc_shadow_mmu_root_page_role(vcpu, false);
+
+ if (new_role.as_u64 != context->mmu_role.as_u64)
+ shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role);
+}
+EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);
static union kvm_mmu_role
kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 6bceafb19108..e424bce13e6c 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -87,7 +87,8 @@ static void nested_svm_init_mmu_context(struct kvm_vcpu *vcpu)
WARN_ON(mmu_is_nested(vcpu));
vcpu->arch.mmu = &vcpu->arch.guest_mmu;
- kvm_init_shadow_mmu(vcpu, X86_CR0_PG, hsave->save.cr4, hsave->save.efer);
+ kvm_init_shadow_npt_mmu(vcpu, X86_CR0_PG, hsave->save.cr4, hsave->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;
vcpu->arch.mmu->inject_page_fault = nested_svm_inject_npf_exit;
--
2.25.4
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest
2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov
2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov
@ 2020-07-08 9:36 ` Vitaly Kuznetsov
2020-07-08 11:49 ` Paolo Bonzini
2020-07-08 9:36 ` [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov
2 siblings, 1 reply; 7+ messages in thread
From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw)
To: kvm, Paolo Bonzini
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid,
linux-kernel
Undesired triple fault gets injected to L1 guest on SVM when L2 is
launched with certain CR3 values. #TF is raised by mmu_check_root()
check in fast_pgd_switch() and the root cause is that when
kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT
enabled CR3 points to a nGPA so we can't check it with
kvm_is_visible_gfn().
Calling kvm_mmu_new_pgd() with L2's CR3 idea when NPT is in use
seems to be wrong, an acceptable place for it seems to be
kvm_init_shadow_npt_mmu(). This also matches nVMX code.
Fixes: 7c390d350f8b ("kvm: x86: Add fast CR3 switch code path")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 7 ++++++-
arch/x86/kvm/mmu/mmu.c | 2 ++
arch/x86/kvm/svm/nested.c | 2 +-
arch/x86/kvm/x86.c | 8 +++++---
4 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index be5363b21540..49b62f024f51 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1459,7 +1459,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
int reason, bool has_error_code, u32 error_code);
int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
-int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
+int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested);
+static inline int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
+{
+ return __kvm_set_cr3(vcpu, cr3, false);
+}
+
int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8);
int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 167d12ab957a..ebf0cb3f1ce0 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4987,6 +4987,8 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
union kvm_mmu_role new_role =
kvm_calc_shadow_mmu_root_page_role(vcpu, false);
+ __kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base, true, true);
+
if (new_role.as_u64 != context->mmu_role.as_u64)
shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role);
}
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index e424bce13e6c..b467917a9784 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -324,7 +324,7 @@ static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_v
svm_set_efer(&svm->vcpu, nested_vmcb->save.efer);
svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0);
svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4);
- (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3);
+ (void)__kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3, npt_enabled);
svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = nested_vmcb->save.cr2;
kvm_rax_write(&svm->vcpu, nested_vmcb->save.rax);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3b92db412335..3761135eb052 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1004,7 +1004,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
}
EXPORT_SYMBOL_GPL(kvm_set_cr4);
-int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
+int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested)
{
bool skip_tlb_flush = false;
#ifdef CONFIG_X86_64
@@ -1031,13 +1031,15 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
return 1;
- kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);
+ if (!cr3_is_nested)
+ kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);
+
vcpu->arch.cr3 = cr3;
kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
return 0;
}
-EXPORT_SYMBOL_GPL(kvm_set_cr3);
+EXPORT_SYMBOL_GPL(__kvm_set_cr3);
int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8)
{
--
2.25.4
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch()
2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov
2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov
2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov
@ 2020-07-08 9:36 ` Vitaly Kuznetsov
2 siblings, 0 replies; 7+ messages in thread
From: Vitaly Kuznetsov @ 2020-07-08 9:36 UTC (permalink / raw)
To: kvm, Paolo Bonzini
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid,
linux-kernel
The mmu_check_root() check in fast_pgd_switch() seems to be
superfluous: when GPA is outside of the visible range
cached_root_available() will fail for non-direct roots
(as we can't have a matching one on the list) and we don't
seem to care for direct ones.
Also, raising #TF immediately when a non-existent GFN is written to CR3
doesn't seem to mach architectural behavior. Drop the check.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/mmu/mmu.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index ebf0cb3f1ce0..16c7701f1741 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4277,8 +4277,7 @@ static bool fast_pgd_switch(struct kvm_vcpu *vcpu, gpa_t new_pgd,
*/
if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL &&
mmu->root_level >= PT64_ROOT_4LEVEL)
- return !mmu_check_root(vcpu, new_pgd >> PAGE_SHIFT) &&
- cached_root_available(vcpu, new_pgd, new_role);
+ return cached_root_available(vcpu, new_pgd, new_role);
return false;
}
--
2.25.4
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu()
2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov
@ 2020-07-08 11:25 ` Paolo Bonzini
0 siblings, 0 replies; 7+ messages in thread
From: Paolo Bonzini @ 2020-07-08 11:25 UTC (permalink / raw)
To: Vitaly Kuznetsov, kvm
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid,
linux-kernel
On 08/07/20 11:36, Vitaly Kuznetsov wrote:
> @@ -4973,7 +4969,28 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer)
> context->mmu_role.as_u64 = new_role.as_u64;
> reset_shadow_zero_bits_mask(vcpu, context);
> }
> -EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
> +
> +static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer)
> +{
> + struct kvm_mmu *context = vcpu->arch.mmu;
> + union kvm_mmu_role new_role =
> + kvm_calc_shadow_mmu_root_page_role(vcpu, false);
> +
> + if (new_role.as_u64 != context->mmu_role.as_u64)
> + shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role);
> +}
> +
> +void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
> + gpa_t nested_cr3)
> +{
> + struct kvm_mmu *context = vcpu->arch.mmu;
> + union kvm_mmu_role new_role =
> + kvm_calc_shadow_mmu_root_page_role(vcpu, false);
> +
> + if (new_role.as_u64 != context->mmu_role.as_u64)
> + shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role);
> +}
> +EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);
>
> static union kvm_mmu_role
As a follow up, the assignments to context should stop using
vcpu->arch.mmu in favor of root_mmu/guest_mmu.
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest
2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov
@ 2020-07-08 11:49 ` Paolo Bonzini
2020-07-08 14:39 ` Vitaly Kuznetsov
0 siblings, 1 reply; 7+ messages in thread
From: Paolo Bonzini @ 2020-07-08 11:49 UTC (permalink / raw)
To: Vitaly Kuznetsov, kvm
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid,
linux-kernel
On 08/07/20 11:36, Vitaly Kuznetsov wrote:
> Undesired triple fault gets injected to L1 guest on SVM when L2 is
> launched with certain CR3 values. #TF is raised by mmu_check_root()
> check in fast_pgd_switch() and the root cause is that when
> kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT
> enabled CR3 points to a nGPA so we can't check it with
> kvm_is_visible_gfn().
>
> Calling kvm_mmu_new_pgd() with L2's CR3 idea when NPT is in use
> seems to be wrong, an acceptable place for it seems to be
> kvm_init_shadow_npt_mmu(). This also matches nVMX code.
>
> Fixes: 7c390d350f8b ("kvm: x86: Add fast CR3 switch code path")
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 7 ++++++-
> arch/x86/kvm/mmu/mmu.c | 2 ++
> arch/x86/kvm/svm/nested.c | 2 +-
> arch/x86/kvm/x86.c | 8 +++++---
> 4 files changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index be5363b21540..49b62f024f51 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1459,7 +1459,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
> int reason, bool has_error_code, u32 error_code);
>
> int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
> -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
> +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested);
> +static inline int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> +{
> + return __kvm_set_cr3(vcpu, cr3, false);
> +}
> +
> int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
> int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8);
> int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val);
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 167d12ab957a..ebf0cb3f1ce0 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4987,6 +4987,8 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
> union kvm_mmu_role new_role =
> kvm_calc_shadow_mmu_root_page_role(vcpu, false);
>
> + __kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base, true, true);
> +
> if (new_role.as_u64 != context->mmu_role.as_u64)
> shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role);
> }
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index e424bce13e6c..b467917a9784 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -324,7 +324,7 @@ static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_v
> svm_set_efer(&svm->vcpu, nested_vmcb->save.efer);
> svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0);
> svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4);
> - (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3);
> + (void)__kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3, npt_enabled);
>
> svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = nested_vmcb->save.cr2;
> kvm_rax_write(&svm->vcpu, nested_vmcb->save.rax);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3b92db412335..3761135eb052 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1004,7 +1004,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> }
> EXPORT_SYMBOL_GPL(kvm_set_cr4);
>
> -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested)
> {
> bool skip_tlb_flush = false;
> #ifdef CONFIG_X86_64
> @@ -1031,13 +1031,15 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
> return 1;
>
> - kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);
> + if (!cr3_is_nested)
> + kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);
> +
> vcpu->arch.cr3 = cr3;
> kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
>
> return 0;
> }
> -EXPORT_SYMBOL_GPL(kvm_set_cr3);
> +EXPORT_SYMBOL_GPL(__kvm_set_cr3);
>
> int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8)
> {
>
Instead of the new argument (which is not really named right since it's
never true for !NPT) you could perhaps check vcpu->arch.mmu. But also,
for NPT=1 the kvm_mmu_new_pgd is also unnecessary on vmexit, because the
old roots are still valid (or has been invalidated otherwise) while L2
was running.
I'm also not sure if skip_tlb_flush can use X86_CR3_PCID_NOFLUSH the way
kvm_set_cr3 does, so I wouldn't mind duplicating the code completely as
is already the case for nested_vmx_load_cr3. It would introduce some
code duplication, but overall the code would be better. For now, there
need not be an equivalent to nested_vmx_transition_mmu_sync, ASID
handling can be left for later.
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest
2020-07-08 11:49 ` Paolo Bonzini
@ 2020-07-08 14:39 ` Vitaly Kuznetsov
0 siblings, 0 replies; 7+ messages in thread
From: Vitaly Kuznetsov @ 2020-07-08 14:39 UTC (permalink / raw)
To: Paolo Bonzini, kvm
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, Junaid Shahid,
linux-kernel
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 08/07/20 11:36, Vitaly Kuznetsov wrote:
>> Undesired triple fault gets injected to L1 guest on SVM when L2 is
>> launched with certain CR3 values. #TF is raised by mmu_check_root()
>> check in fast_pgd_switch() and the root cause is that when
>> kvm_set_cr3() is called from nested_prepare_vmcb_save() with NPT
>> enabled CR3 points to a nGPA so we can't check it with
>> kvm_is_visible_gfn().
>>
>> Calling kvm_mmu_new_pgd() with L2's CR3 idea when NPT is in use
>> seems to be wrong, an acceptable place for it seems to be
>> kvm_init_shadow_npt_mmu(). This also matches nVMX code.
>>
>> Fixes: 7c390d350f8b ("kvm: x86: Add fast CR3 switch code path")
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> arch/x86/include/asm/kvm_host.h | 7 ++++++-
>> arch/x86/kvm/mmu/mmu.c | 2 ++
>> arch/x86/kvm/svm/nested.c | 2 +-
>> arch/x86/kvm/x86.c | 8 +++++---
>> 4 files changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index be5363b21540..49b62f024f51 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -1459,7 +1459,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
>> int reason, bool has_error_code, u32 error_code);
>>
>> int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
>> -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
>> +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested);
>> +static inline int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>> +{
>> + return __kvm_set_cr3(vcpu, cr3, false);
>> +}
>> +
>> int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
>> int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8);
>> int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val);
>> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
>> index 167d12ab957a..ebf0cb3f1ce0 100644
>> --- a/arch/x86/kvm/mmu/mmu.c
>> +++ b/arch/x86/kvm/mmu/mmu.c
>> @@ -4987,6 +4987,8 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, u32 cr0, u32 cr4, u32 efer,
>> union kvm_mmu_role new_role =
>> kvm_calc_shadow_mmu_root_page_role(vcpu, false);
>>
>> + __kvm_mmu_new_pgd(vcpu, nested_cr3, new_role.base, true, true);
>> +
>> if (new_role.as_u64 != context->mmu_role.as_u64)
>> shadow_mmu_init_context(vcpu, cr0, cr4, efer, new_role);
>> }
>> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
>> index e424bce13e6c..b467917a9784 100644
>> --- a/arch/x86/kvm/svm/nested.c
>> +++ b/arch/x86/kvm/svm/nested.c
>> @@ -324,7 +324,7 @@ static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_v
>> svm_set_efer(&svm->vcpu, nested_vmcb->save.efer);
>> svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0);
>> svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4);
>> - (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3);
>> + (void)__kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3, npt_enabled);
>>
>> svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = nested_vmcb->save.cr2;
>> kvm_rax_write(&svm->vcpu, nested_vmcb->save.rax);
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 3b92db412335..3761135eb052 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -1004,7 +1004,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
>> }
>> EXPORT_SYMBOL_GPL(kvm_set_cr4);
>>
>> -int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>> +int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool cr3_is_nested)
>> {
>> bool skip_tlb_flush = false;
>> #ifdef CONFIG_X86_64
>> @@ -1031,13 +1031,15 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>> !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
>> return 1;
>>
>> - kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);
>> + if (!cr3_is_nested)
>> + kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);
>> +
>> vcpu->arch.cr3 = cr3;
>> kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
>>
>> return 0;
>> }
>> -EXPORT_SYMBOL_GPL(kvm_set_cr3);
>> +EXPORT_SYMBOL_GPL(__kvm_set_cr3);
>>
>> int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8)
>> {
>>
>
> Instead of the new argument (which is not really named right since it's
> never true for !NPT) you could perhaps check vcpu->arch.mmu. But also,
> for NPT=1 the kvm_mmu_new_pgd is also unnecessary on vmexit, because the
> old roots are still valid (or has been invalidated otherwise) while L2
> was running.
>
> I'm also not sure if skip_tlb_flush can use X86_CR3_PCID_NOFLUSH the way
> kvm_set_cr3 does, so I wouldn't mind duplicating the code completely as
> is already the case for nested_vmx_load_cr3. It would introduce some
> code duplication, but overall the code would be better. For now, there
> need not be an equivalent to nested_vmx_transition_mmu_sync, ASID
> handling can be left for later.
Sounds reasonable,
let's introduce nested_svm_load_cr3() to not mix these two concepts
together. I'll be back with v3 shortly, thanks!
--
Vitaly
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-07-08 14:39 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-08 9:36 [PATCH v2 0/3] KVM: nSVM: fix #TF from CR3 switch when entering guest Vitaly Kuznetsov
2020-07-08 9:36 ` [PATCH v2 1/3] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov
2020-07-08 11:25 ` Paolo Bonzini
2020-07-08 9:36 ` [PATCH v2 2/3] KVM: nSVM: properly call kvm_mmu_new_pgd() upon switching to guest Vitaly Kuznetsov
2020-07-08 11:49 ` Paolo Bonzini
2020-07-08 14:39 ` Vitaly Kuznetsov
2020-07-08 9:36 ` [PATCH v2 3/3] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov
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