[PATCH 0/7] KVM: arm64: Fix missing ESR_ELx.IL in syndrome injection

[PATCH 0/7] KVM: arm64: Fix missing ESR_ELx.IL in syndrome injection

[Fuad Tabba]

Hi folks,

After sashiko caught the missing IL bug [1], I did an audit of all ESR
syndrome construction sites in KVM/arm64 as Marc suggested. This series
is the result of that audit.

The ARM architecture mandates ESR_ELx.IL=1 for several exception
classes regardless of instruction length: EC=Unknown, Instruction
Aborts, Data Aborts with ISV=0, and SError. For FPAC (EC=0x1C), IL
reflects instruction length, but FPAC can only be generated by A64
instructions, so IL must also be 1.

Patch 1 is the bug sashiko found: inject_undef64() in the pKVM hyp (EL2)
path never set IL.
Patch 2 makes the same fix to inject_undef64() in the normal host path,
where IL was derived from the triggering trap's instruction length. No
instruction that reaches undef injection has a 16-bit encoding, so patch
2 has no functional change today.
Patch 3 makes the matching fix to inject_abt64(). Unlike undef injection,
abort injection is reachable from a 16-bit T32 instruction (a 32-bit EL0
task under an AArch64 EL1 guest), so the old code there injects an abort
with IL=0.
Patch 4 fixes the FPAC syndrome constructed during nested ERET
emulation, which did not set IL.
Patches 5-6 fix SError injection in the emulated and nested paths,
neither of which set IL.
Patch 7 fixes a fake ESR used to exit to the host. The host does not
read IL there, so it is not guest-visible.

Based on Linux 7.1-rc7

Cheers,
/fuad

[1] https://lore.kernel.org/all/87pl1t8q24.wl-maz@kernel.org/

Fuad Tabba (7):
  KVM: arm64: Set ESR_ELx.IL for injected undefined exceptions at EL2
  KVM: arm64: Unconditionally set IL for injected undefined exceptions
  KVM: arm64: Unconditionally set IL for injected abort exceptions
  KVM: arm64: Set IL for injected FPAC exceptions during ERET emulation
  KVM: arm64: Set IL for emulated SError injection
  KVM: arm64: Set IL for nested SError injection
  KVM: arm64: Set IL in fake ESR for pKVM memory sharing exit

 arch/arm64/kvm/emulate-nested.c    |  4 ++--
 arch/arm64/kvm/hyp/nvhe/pkvm.c     |  3 ++-
 arch/arm64/kvm/hyp/nvhe/sys_regs.c |  2 +-
 arch/arm64/kvm/inject_fault.c      | 18 +++++-------------
 4 files changed, 10 insertions(+), 17 deletions(-)

-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH 1/7] KVM: arm64: Set ESR_ELx.IL for injected undefined exceptions at EL2

[Fuad Tabba]

inject_undef64() constructs an ESR with EC=0 (Unknown) but does not set
IL. The architecture mandates IL=1 for EC=0 unconditionally (ARM DDI
0487, ESR_ELx.IL description), so the injected syndrome is one that
conforming hardware cannot produce.

Set ESR_ELx_IL in the constructed syndrome.

Fixes: e5d40a5a97c1 ("KVM: arm64: pkvm: Add a generic synchronous exception injection primitive")
Reported-by: sashiko <sashiko@sashiko.dev>
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/hyp/nvhe/sys_regs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/sys_regs.c b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
index 8c3fbb413a06..9767adf1f73e 100644
--- a/arch/arm64/kvm/hyp/nvhe/sys_regs.c
+++ b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
@@ -278,7 +278,7 @@ static void inject_sync64(struct kvm_vcpu *vcpu, u64 esr)
  */
 static void inject_undef64(struct kvm_vcpu *vcpu)
 {
-	inject_sync64(vcpu, (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT));
+	inject_sync64(vcpu, (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT) | ESR_ELx_IL);
 }
 
 static u64 read_id_reg(const struct kvm_vcpu *vcpu,
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH 2/7] KVM: arm64: Unconditionally set IL for injected undefined exceptions

[Fuad Tabba]

inject_undef64() derives IL from the triggering trap's instruction
length (kvm_vcpu_trap_il_is32bit()), but the IL of the injected
exception is fixed by its EC, not by the triggering instruction. The
architecture mandates IL=1 for EC=0 (Unknown) unconditionally, so the
conditional is wrong. The undef-injection paths are not reached from
16-bit instructions, so there is no functional change today, but the
logic should not rely on that.

Set ESR_ELx_IL unconditionally.

Fixes: aa8eff9bfbd5 ("arm64: KVM: fault injection into a guest")
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/inject_fault.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index 89982bd3345f..9dfae1bcdf99 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -170,14 +170,7 @@ void kvm_inject_sync(struct kvm_vcpu *vcpu, u64 esr)
 
 static void inject_undef64(struct kvm_vcpu *vcpu)
 {
-	u64 esr = (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT);
-
-	/*
-	 * Build an unknown exception, depending on the instruction
-	 * set.
-	 */
-	if (kvm_vcpu_trap_il_is32bit(vcpu))
-		esr |= ESR_ELx_IL;
+	u64 esr = (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT) | ESR_ELx_IL;
 
 	kvm_inject_sync(vcpu, esr);
 }
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH 3/7] KVM: arm64: Unconditionally set IL for injected abort exceptions

[Fuad Tabba]

inject_abt64() derives IL from the triggering trap's instruction length
(kvm_vcpu_trap_il_is32bit()), but the IL of the injected abort is fixed
by its EC, not by the triggering instruction. The architecture mandates
IL=1 for Instruction Aborts unconditionally and for Data Aborts with
ISV=0, and this function never sets ISV (the FSC is always EXTABT or
SEA_TTW). For a 16-bit T32 trap (a 32-bit EL0 task under an AArch64 EL1
guest) the trap has IL=0, so the abort is injected with the wrong IL.

Set ESR_ELx_IL unconditionally.

Fixes: aa8eff9bfbd5 ("arm64: KVM: fault injection into a guest")
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/inject_fault.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index 9dfae1bcdf99..444d219b0217 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -138,11 +138,10 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
 		pend_sync_exception(vcpu);
 
 	/*
-	 * Build an {i,d}abort, depending on the level and the
-	 * instruction set. Report an external synchronous abort.
+	 * Build an {i,d}abort, depending on the level.
+	 * Report an external synchronous abort.
 	 */
-	if (kvm_vcpu_trap_il_is32bit(vcpu))
-		esr |= ESR_ELx_IL;
+	esr |= ESR_ELx_IL;
 
 	/*
 	 * Here, the guest runs in AArch64 mode when in EL1. If we get
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH 4/7] KVM: arm64: Set IL for injected FPAC exceptions during ERET emulation

[Fuad Tabba]

The FPAC syndrome constructed during nested ERET emulation does not set
IL. For FPAC (EC=0x1C), IL reflects the instruction length. ERET and
its authenticated variants are always A64 32-bit instructions, so IL
must be 1.

Fixes: 213b3d1ea161 ("KVM: arm64: nv: Handle ERETA[AB] instructions")
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/emulate-nested.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index dba7ced74ca5..4b39363cf891 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -2777,7 +2777,7 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu)
 		 */
 		if (kvm_has_pauth(vcpu->kvm, FPACCOMBINE) && !(spsr & PSR_IL_BIT)) {
 			esr &= ESR_ELx_ERET_ISS_ERETA;
-			esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_FPAC);
+			esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_FPAC) | ESR_ELx_IL;
 			kvm_inject_nested_sync(vcpu, esr);
 			return;
 		}
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH 5/7] KVM: arm64: Set IL for emulated SError injection

[Fuad Tabba]

kvm_inject_serror_esr() constructs an SError syndrome without IL. The
architecture mandates IL=1 for SError unconditionally.

Fixes: f6e2262dfa1a ("KVM: arm64: Populate ESR_ELx.EC for emulated SError injection")
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/inject_fault.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index 444d219b0217..d6c4fc16f879 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -381,7 +381,7 @@ int kvm_inject_serror_esr(struct kvm_vcpu *vcpu, u64 esr)
 	 */
 	if (!serror_is_masked(vcpu)) {
 		pend_serror_exception(vcpu);
-		esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_SERROR);
+		esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_SERROR) | ESR_ELx_IL;
 		vcpu_write_sys_reg(vcpu, esr, exception_esr_elx(vcpu));
 		return 1;
 	}
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH 6/7] KVM: arm64: Set IL for nested SError injection

[Fuad Tabba]

kvm_inject_nested_serror() constructs an SError syndrome without IL.
The architecture mandates IL=1 for SError unconditionally.

Fixes: 77ee70a07357 ("KVM: arm64: nv: Honor SError exception routing / masking")
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/emulate-nested.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index 4b39363cf891..4262d4c17a87 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -2938,6 +2938,6 @@ int kvm_inject_nested_serror(struct kvm_vcpu *vcpu, u64 esr)
 	 * vSError injection. Manually populate EC for an emulated SError
 	 * exception.
 	 */
-	esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_SERROR);
+	esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_SERROR) | ESR_ELx_IL;
 	return kvm_inject_nested(vcpu, esr, except_type_serror);
 }
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH 7/7] KVM: arm64: Set IL in fake ESR for pKVM memory sharing exit

[Fuad Tabba]

__pkvm_memshare_page_req() constructs a fake DABT ESR_EL2 to exit to
the host without setting IL. The ESR has ISV=0, so IL must be 1 per the
architecture. The host does not read IL on this path, but the
constructed syndrome should still be architecturally valid.

Set ESR_ELx_IL.

Fixes: 03313efed5e2 ("KVM: arm64: Implement the MEM_SHARE hypercall for protected VMs")
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/hyp/nvhe/pkvm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index eb1c10120f9f..c982a3a04c37 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -1054,7 +1054,8 @@ static u64 __pkvm_memshare_page_req(struct kvm_vcpu *vcpu, u64 ipa)
 
 	/* Fake up a data abort (level 3 translation fault on write) */
 	vcpu->arch.fault.esr_el2 = (ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT) |
-				   ESR_ELx_WNR | ESR_ELx_FSC_FAULT |
+				   ESR_ELx_IL | ESR_ELx_WNR |
+				   ESR_ELx_FSC_FAULT |
 				   FIELD_PREP(ESR_ELx_FSC_LEVEL, 3);
 
 	/* Shuffle the IPA around into the HPFAR */
-- 
2.54.0.1136.gdb2ca164c4-goog

Re: [PATCH 4/7] KVM: arm64: Set IL for injected FPAC exceptions during ERET emulation

[Marc Zyngier]

On Sun, 14 Jun 2026 17:33:33 +0100,
Fuad Tabba <tabba@google.com> wrote:
> 
> The FPAC syndrome constructed during nested ERET emulation does not set
> IL. For FPAC (EC=0x1C), IL reflects the instruction length. ERET and
> its authenticated variants are always A64 32-bit instructions, so IL
> must be 1.
> 
> Fixes: 213b3d1ea161 ("KVM: arm64: nv: Handle ERETA[AB] instructions")
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
>  arch/arm64/kvm/emulate-nested.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> index dba7ced74ca5..4b39363cf891 100644
> --- a/arch/arm64/kvm/emulate-nested.c
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -2777,7 +2777,7 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu)
>  		 */
>  		if (kvm_has_pauth(vcpu->kvm, FPACCOMBINE) && !(spsr & PSR_IL_BIT)) {
>  			esr &= ESR_ELx_ERET_ISS_ERETA;
> -			esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_FPAC);
> +			esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_FPAC) | ESR_ELx_IL;

In general, I prefer retaining information that is present in the
source exception, rather than adding arbitrary bits without much
context, even if we only support AArch64 for NV. In this case, I'd
rather see this:

			esr &= (ESR_ELx_ERET_ISS_ERETA | ESR_ELx_IL);

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH 4/7] KVM: arm64: Set IL for injected FPAC exceptions during ERET emulation

[Fuad Tabba]

On Thu, 18 Jun 2026 at 09:00, Marc Zyngier <maz@kernel.org> wrote:
>
> On Sun, 14 Jun 2026 17:33:33 +0100,
> Fuad Tabba <tabba@google.com> wrote:
> >
> > The FPAC syndrome constructed during nested ERET emulation does not set
> > IL. For FPAC (EC=0x1C), IL reflects the instruction length. ERET and
> > its authenticated variants are always A64 32-bit instructions, so IL
> > must be 1.
> >
> > Fixes: 213b3d1ea161 ("KVM: arm64: nv: Handle ERETA[AB] instructions")
> > Signed-off-by: Fuad Tabba <tabba@google.com>
> > ---
> >  arch/arm64/kvm/emulate-nested.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> > index dba7ced74ca5..4b39363cf891 100644
> > --- a/arch/arm64/kvm/emulate-nested.c
> > +++ b/arch/arm64/kvm/emulate-nested.c
> > @@ -2777,7 +2777,7 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu)
> >                */
> >               if (kvm_has_pauth(vcpu->kvm, FPACCOMBINE) && !(spsr & PSR_IL_BIT)) {
> >                       esr &= ESR_ELx_ERET_ISS_ERETA;
> > -                     esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_FPAC);
> > +                     esr |= FIELD_PREP(ESR_ELx_EC_MASK, ESR_ELx_EC_FPAC) | ESR_ELx_IL;
>
> In general, I prefer retaining information that is present in the
> source exception, rather than adding arbitrary bits without much
> context, even if we only support AArch64 for NV. In this case, I'd
> rather see this:
>
>                         esr &= (ESR_ELx_ERET_ISS_ERETA | ESR_ELx_IL);

Sounds good to me. I'll rebase on 7.1 and respin.

Cheers,
/fuad

>
> Thanks,
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.