From mboxrd@z Thu Jan 1 00:00:00 1970 From: christoffer.dall@linaro.org (Christoffer Dall) Date: Wed, 7 Feb 2018 09:32:51 +0100 Subject: [PATCH v4 02/17] arm: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls In-Reply-To: <20180206175621.929-3-marc.zyngier@arm.com> References: <20180206175621.929-1-marc.zyngier@arm.com> <20180206175621.929-3-marc.zyngier@arm.com> Message-ID: <20180207083251.GB29286@cbox> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Feb 06, 2018 at 05:56:06PM +0000, Marc Zyngier wrote: > KVM doesn't follow the SMCCC when it comes to unimplemented calls, > and inject an UNDEF instead of returning an error. Since firmware > calls are now used for security mitigation, they are becoming more > common, and the undef is counter productive. > > Instead, let's follow the SMCCC which states that -1 must be returned > to the caller when getting an unknown function number. Apparently I forgot to review this: Reviewed-by: Christoffer Dall > > Cc: > Tested-by: Ard Biesheuvel > Signed-off-by: Marc Zyngier > --- > arch/arm/kvm/handle_exit.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c > index cf8bf6bf87c4..a4bf0f6f024a 100644 > --- a/arch/arm/kvm/handle_exit.c > +++ b/arch/arm/kvm/handle_exit.c > @@ -38,7 +38,7 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run) > > ret = kvm_psci_call(vcpu); > if (ret < 0) { > - kvm_inject_undefined(vcpu); > + vcpu_set_reg(vcpu, 0, ~0UL); > return 1; > } > > @@ -47,7 +47,16 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run) > > static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run) > { > - kvm_inject_undefined(vcpu); > + /* > + * "If an SMC instruction executed at Non-secure EL1 is > + * trapped to EL2 because HCR_EL2.TSC is 1, the exception is a > + * Trap exception, not a Secure Monitor Call exception [...]" > + * > + * We need to advance the PC after the trap, as it would > + * otherwise return to the same address... > + */ > + vcpu_set_reg(vcpu, 0, ~0UL); > + kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu)); > return 1; > } > > -- > 2.14.2 >