[GIT PULL] KVM/arm64 fixes for 5.9, take #2

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* [GIT PULL] KVM/arm64 fixes for 5.9, take #2
@ 2020-09-18 17:16 Marc Zyngier
  2020-09-18 17:16 ` [PATCH 1/2] KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch Marc Zyngier
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Marc Zyngier @ 2020-09-18 17:16 UTC (permalink / raw)
  To: Paolo Bonzini
  Cc: Will Deacon, kernel-team, linux-arm-kernel, kvmarm, kvm,
	James Morse, Julien Thierry, Suzuki K Poulose

Hi Paolo,

Here's the latest set of fixes for 5.9. The first patch is pretty
nasty, as a guest hitting this bug will have its vcpu stuck on a
fault, without any hope of it being resolved. Embarrassing, and
definitely a stable candidate. The second patch is only a cleanup
after the first one.

Please pull,

	M.

The following changes since commit 7b75cd5128421c673153efb1236705696a1a9812:

  KVM: arm64: Update page shift if stage 2 block mapping not supported (2020-09-04 10:53:48 +0100)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git tags/kvmarm-fixes-5.9-2

for you to fetch changes up to 620cf45f7a516bf5fe9e5dce675a652e935c8bde:

  KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite() (2020-09-18 18:01:48 +0100)

----------------------------------------------------------------
KVM/arm64 fixes for 5.9, take #2

- Fix handling of S1 Page Table Walk permission fault at S2
  on instruction fetch
- Cleanup kvm_vcpu_dabt_iswrite()

----------------------------------------------------------------
Marc Zyngier (2):
      KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch
      KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite()

 arch/arm64/include/asm/kvm_emulate.h    | 14 +++++++++++---
 arch/arm64/kvm/hyp/include/hyp/switch.h |  2 +-
 arch/arm64/kvm/mmu.c                    |  4 ++--
 3 files changed, 14 insertions(+), 6 deletions(-)

^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH 1/2] KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch
  2020-09-18 17:16 [GIT PULL] KVM/arm64 fixes for 5.9, take #2 Marc Zyngier
@ 2020-09-18 17:16 ` Marc Zyngier
  2020-09-18 17:16 ` [PATCH 2/2] KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite() Marc Zyngier
  2020-09-20 13:14 ` [GIT PULL] KVM/arm64 fixes for 5.9, take #2 Paolo Bonzini
  2 siblings, 0 replies; 4+ messages in thread
From: Marc Zyngier @ 2020-09-18 17:16 UTC (permalink / raw)
  To: Paolo Bonzini
  Cc: Will Deacon, kernel-team, linux-arm-kernel, kvmarm, kvm,
	James Morse, Julien Thierry, Suzuki K Poulose, stable

KVM currently assumes that an instruction abort can never be a write.
This is in general true, except when the abort is triggered by
a S1PTW on instruction fetch that tries to update the S1 page tables
(to set AF, for example).

This can happen if the page tables have been paged out and brought
back in without seeing a direct write to them (they are thus marked
read only), and the fault handling code will make the PT executable(!)
instead of writable. The guest gets stuck forever.

In these conditions, the permission fault must be considered as
a write so that the Stage-1 update can take place. This is essentially
the I-side equivalent of the problem fixed by 60e21a0ef54c ("arm64: KVM:
Take S1 walks into account when determining S2 write faults").

Update kvm_is_write_fault() to return true on IABT+S1PTW, and introduce
kvm_vcpu_trap_is_exec_fault() that only return true when no faulting
on a S1 fault. Additionally, kvm_vcpu_dabt_iss1tw() is renamed to
kvm_vcpu_abt_iss1tw(), as the above makes it plain that it isn't
specific to data abort.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Will Deacon <will@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200915104218.1284701-2-maz@kernel.org
---
 arch/arm64/include/asm/kvm_emulate.h    | 12 ++++++++++--
 arch/arm64/kvm/hyp/include/hyp/switch.h |  2 +-
 arch/arm64/kvm/mmu.c                    |  4 ++--
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 49a55be2b9a2..4f618af660ba 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -298,7 +298,7 @@ static __always_inline int kvm_vcpu_dabt_get_rd(const struct kvm_vcpu *vcpu)
 	return (kvm_vcpu_get_esr(vcpu) & ESR_ELx_SRT_MASK) >> ESR_ELx_SRT_SHIFT;
 }
 
-static __always_inline bool kvm_vcpu_dabt_iss1tw(const struct kvm_vcpu *vcpu)
+static __always_inline bool kvm_vcpu_abt_iss1tw(const struct kvm_vcpu *vcpu)
 {
 	return !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_S1PTW);
 }
@@ -306,7 +306,7 @@ static __always_inline bool kvm_vcpu_dabt_iss1tw(const struct kvm_vcpu *vcpu)
 static __always_inline bool kvm_vcpu_dabt_iswrite(const struct kvm_vcpu *vcpu)
 {
 	return !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_WNR) ||
-		kvm_vcpu_dabt_iss1tw(vcpu); /* AF/DBM update */
+		kvm_vcpu_abt_iss1tw(vcpu); /* AF/DBM update */
 }
 
 static inline bool kvm_vcpu_dabt_is_cm(const struct kvm_vcpu *vcpu)
@@ -335,6 +335,11 @@ static inline bool kvm_vcpu_trap_is_iabt(const struct kvm_vcpu *vcpu)
 	return kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_IABT_LOW;
 }
 
+static inline bool kvm_vcpu_trap_is_exec_fault(const struct kvm_vcpu *vcpu)
+{
+	return kvm_vcpu_trap_is_iabt(vcpu) && !kvm_vcpu_abt_iss1tw(vcpu);
+}
+
 static __always_inline u8 kvm_vcpu_trap_get_fault(const struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC;
@@ -372,6 +377,9 @@ static __always_inline int kvm_vcpu_sys_get_rt(struct kvm_vcpu *vcpu)
 
 static inline bool kvm_is_write_fault(struct kvm_vcpu *vcpu)
 {
+	if (kvm_vcpu_abt_iss1tw(vcpu))
+		return true;
+
 	if (kvm_vcpu_trap_is_iabt(vcpu))
 		return false;
 
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 426ef65601dd..d64c5d56c860 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -445,7 +445,7 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 			kvm_vcpu_trap_get_fault_type(vcpu) == FSC_FAULT &&
 			kvm_vcpu_dabt_isvalid(vcpu) &&
 			!kvm_vcpu_abt_issea(vcpu) &&
-			!kvm_vcpu_dabt_iss1tw(vcpu);
+			!kvm_vcpu_abt_iss1tw(vcpu);
 
 		if (valid) {
 			int ret = __vgic_v2_perform_cpuif_access(vcpu);
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index f58d657a898d..9aec1ce491d2 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1843,7 +1843,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	struct kvm_s2_mmu *mmu = vcpu->arch.hw_mmu;
 
 	write_fault = kvm_is_write_fault(vcpu);
-	exec_fault = kvm_vcpu_trap_is_iabt(vcpu);
+	exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu);
 	VM_BUG_ON(write_fault && exec_fault);
 
 	if (fault_status == FSC_PERM && !write_fault && !exec_fault) {
@@ -2125,7 +2125,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 			goto out;
 		}
 
-		if (kvm_vcpu_dabt_iss1tw(vcpu)) {
+		if (kvm_vcpu_abt_iss1tw(vcpu)) {
 			kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
 			ret = 1;
 			goto out_unlock;
-- 
2.28.0


^ permalink raw reply related	[flat|nested] 4+ messages in thread

* [PATCH 2/2] KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite()
  2020-09-18 17:16 [GIT PULL] KVM/arm64 fixes for 5.9, take #2 Marc Zyngier
  2020-09-18 17:16 ` [PATCH 1/2] KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch Marc Zyngier
@ 2020-09-18 17:16 ` Marc Zyngier
  2020-09-20 13:14 ` [GIT PULL] KVM/arm64 fixes for 5.9, take #2 Paolo Bonzini
  2 siblings, 0 replies; 4+ messages in thread
From: Marc Zyngier @ 2020-09-18 17:16 UTC (permalink / raw)
  To: Paolo Bonzini
  Cc: Will Deacon, kernel-team, linux-arm-kernel, kvmarm, kvm,
	James Morse, Julien Thierry, Suzuki K Poulose

Now that kvm_vcpu_trap_is_write_fault() checks for S1PTW, there
is no need for kvm_vcpu_dabt_iswrite() to do the same thing, as
we already check for this condition on all existing paths.

Drop the check and add a comment instead.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200915104218.1284701-3-maz@kernel.org
---
 arch/arm64/include/asm/kvm_emulate.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 4f618af660ba..1cc5f5f72d0b 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -303,10 +303,10 @@ static __always_inline bool kvm_vcpu_abt_iss1tw(const struct kvm_vcpu *vcpu)
 	return !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_S1PTW);
 }
 
+/* Always check for S1PTW *before* using this. */
 static __always_inline bool kvm_vcpu_dabt_iswrite(const struct kvm_vcpu *vcpu)
 {
-	return !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_WNR) ||
-		kvm_vcpu_abt_iss1tw(vcpu); /* AF/DBM update */
+	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_WNR;
 }
 
 static inline bool kvm_vcpu_dabt_is_cm(const struct kvm_vcpu *vcpu)
-- 
2.28.0


^ permalink raw reply related	[flat|nested] 4+ messages in thread

* Re: [GIT PULL] KVM/arm64 fixes for 5.9, take #2
  2020-09-18 17:16 [GIT PULL] KVM/arm64 fixes for 5.9, take #2 Marc Zyngier
  2020-09-18 17:16 ` [PATCH 1/2] KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch Marc Zyngier
  2020-09-18 17:16 ` [PATCH 2/2] KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite() Marc Zyngier
@ 2020-09-20 13:14 ` Paolo Bonzini
  2 siblings, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2020-09-20 13:14 UTC (permalink / raw)
  To: Marc Zyngier
  Cc: Will Deacon, kernel-team, linux-arm-kernel, kvmarm, kvm,
	James Morse, Julien Thierry, Suzuki K Poulose

On 18/09/20 19:16, Marc Zyngier wrote:
> Hi Paolo,
> 
> Here's the latest set of fixes for 5.9. The first patch is pretty
> nasty, as a guest hitting this bug will have its vcpu stuck on a
> fault, without any hope of it being resolved. Embarrassing, and
> definitely a stable candidate. The second patch is only a cleanup
> after the first one.
> 
> Please pull,
> 
> 	M.
> 
> The following changes since commit 7b75cd5128421c673153efb1236705696a1a9812:
> 
>   KVM: arm64: Update page shift if stage 2 block mapping not supported (2020-09-04 10:53:48 +0100)
> 
> are available in the Git repository at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git tags/kvmarm-fixes-5.9-2

Pulled, thanks.

Paolo

> 
> for you to fetch changes up to 620cf45f7a516bf5fe9e5dce675a652e935c8bde:
> 
>   KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite() (2020-09-18 18:01:48 +0100)
> 
> ----------------------------------------------------------------
> KVM/arm64 fixes for 5.9, take #2
> 
> - Fix handling of S1 Page Table Walk permission fault at S2
>   on instruction fetch
> - Cleanup kvm_vcpu_dabt_iswrite()
> 
> ----------------------------------------------------------------
> Marc Zyngier (2):
>       KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch
>       KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite()
> 
>  arch/arm64/include/asm/kvm_emulate.h    | 14 +++++++++++---
>  arch/arm64/kvm/hyp/include/hyp/switch.h |  2 +-
>  arch/arm64/kvm/mmu.c                    |  4 ++--
>  3 files changed, 14 insertions(+), 6 deletions(-)
> 


^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2020-09-20 13:14 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-09-18 17:16 [GIT PULL] KVM/arm64 fixes for 5.9, take #2 Marc Zyngier
2020-09-18 17:16 ` [PATCH 1/2] KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch Marc Zyngier
2020-09-18 17:16 ` [PATCH 2/2] KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite() Marc Zyngier
2020-09-20 13:14 ` [GIT PULL] KVM/arm64 fixes for 5.9, take #2 Paolo Bonzini

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