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Message-ID: <22fb583f-a33e-15f8-a059-fb112b27dd4f@arm.com>
Date: Mon, 20 Mar 2017 13:58:32 +0000
From: Marc Zyngier <marc.zyngier@....com>
To: gengdongjiu <gengdongjiu@...wei.com>, catalin.marinas@....com,
will.deacon@....com, christoffer.dall@...aro.org,
rkrcmar@...hat.com, suzuki.poulose@....com, andre.przywara@....com,
mark.rutland@....com, vladimir.murzin@....com,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: xiexiuqi@...wei.com, wangxiongfeng2@...wei.com,
wuquanming@...wei.com, James Morse <James.Morse@....com>
Subject: Re: [PATCH] kvm: pass the virtual SEI syndrome to guest OS
On 20/03/17 12:28, gengdongjiu wrote:
>
>
> On 2017/3/20 19:24, Marc Zyngier wrote:
>> Please include James Morse on anything RAS related, as he's already
>> looking at related patches.
>>
>> On 20/03/17 07:55, Dongjiu Geng wrote:
>>> In the RAS implementation, hardware pass the virtual SEI
>>> syndrome information through the VSESR_EL2, so set the virtual
>>> SEI syndrome using physical SEI syndrome el2_elr to pass to
>>> the guest OS
>>>
>>> Signed-off-by: Dongjiu Geng <gengdongjiu@...wei.com>
>>> Signed-off-by: Quanming wu <wuquanming@...wei.com>
>>> ---
>>> arch/arm64/Kconfig | 8 ++++++++
>>> arch/arm64/include/asm/esr.h | 1 +
>>> arch/arm64/include/asm/kvm_emulate.h | 12 ++++++++++++
>>> arch/arm64/include/asm/kvm_host.h | 4 ++++
>>> arch/arm64/kvm/hyp/switch.c | 15 ++++++++++++++-
>>> arch/arm64/kvm/inject_fault.c | 10 ++++++++++
>>> 6 files changed, 49 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>>> index 8c7c244247b6..ea62170a3b75 100644
>>> --- a/arch/arm64/Kconfig
>>> +++ b/arch/arm64/Kconfig
>>> @@ -908,6 +908,14 @@ endmenu
>>>
>>> menu "ARMv8.2 architectural features"
>>>
>>> +config HAS_RAS_EXTENSION
>>> + bool "Support arm64 RAS extension"
>>> + default n
>>> + help
>>> + Reliability, Availability, Serviceability(RAS; part of the ARMv8.2 Extensions).
>>> +
>>> + Selecting this option OS will try to recover the error that RAS hardware node detected.
>>> +
>>
>> As this is an architectural extension, this should be controlled by the
>> CPU feature mechanism, and not be chosen at compile time. What you have
>> here will break horribly when booted on a CPU that doesn't implement RAS.
>
> thanks very much for your review, yes, it is, you are right.
>
>>
>>> config ARM64_UAO
>>> bool "Enable support for User Access Override (UAO)"
>>> default y
>>> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
>>> index d14c478976d0..e38d32b2bdad 100644
>>> --- a/arch/arm64/include/asm/esr.h
>>> +++ b/arch/arm64/include/asm/esr.h
>>> @@ -111,6 +111,7 @@
>>> #define ESR_ELx_COND_MASK (UL(0xF) << ESR_ELx_COND_SHIFT)
>>> #define ESR_ELx_WFx_ISS_WFE (UL(1) << 0)
>>> #define ESR_ELx_xVC_IMM_MASK ((1UL << 16) - 1)
>>> +#define VSESR_ELx_IDS_ISS_MASK ((1UL << 25) - 1)
>>>
>>> /* ESR value templates for specific events */
>>>
>>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>>> index f5ea0ba70f07..20d4da7f5dce 100644
>>> --- a/arch/arm64/include/asm/kvm_emulate.h
>>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>>> @@ -148,6 +148,18 @@ static inline u32 kvm_vcpu_get_hsr(const struct kvm_vcpu *vcpu)
>>> return vcpu->arch.fault.esr_el2;
>>> }
>>>
>>> +#ifdef CONFIG_HAS_RAS_EXTENSION
>>> +static inline u32 kvm_vcpu_get_vsesr(const struct kvm_vcpu *vcpu)
>>> +{
>>> + return vcpu->arch.fault.vsesr_el2;
>>> +}
>>> +
>>> +static inline void kvm_vcpu_set_vsesr(struct kvm_vcpu *vcpu, unsigned long val)
>>> +{
>>> + vcpu->arch.fault.vsesr_el2 = val;
>>> +}
>>> +#endif
>>> +
>>> static inline int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
>>> {
>>> u32 esr = kvm_vcpu_get_hsr(vcpu);
>>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>>> index e7705e7bb07b..f9e3bb57c461 100644
>>> --- a/arch/arm64/include/asm/kvm_host.h
>>> +++ b/arch/arm64/include/asm/kvm_host.h
>>> @@ -83,6 +83,10 @@ struct kvm_mmu_memory_cache {
>>> };
>>>
>>> struct kvm_vcpu_fault_info {
>>> +#ifdef CONFIG_HAS_RAS_EXTENSION
>>> + /* Virtual SError Exception Syndrome Register */
>>> + u32 vsesr_el2;
>>> +#endif
>>> u32 esr_el2; /* Hyp Syndrom Register */
>>> u64 far_el2; /* Hyp Fault Address Register */
>>> u64 hpfar_el2; /* Hyp IPA Fault Address Register */
>>> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
>>> index aede1658aeda..770a153fb6ba 100644
>>> --- a/arch/arm64/kvm/hyp/switch.c
>>> +++ b/arch/arm64/kvm/hyp/switch.c
>>> @@ -86,6 +86,13 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>>> isb();
>>> }
>>> write_sysreg(val, hcr_el2);
>>> +#ifdef CONFIG_HAS_RAS_EXTENSION
>>> + /* If virtual System Error or Asynchronous Abort is pending. set
>>> + * the virtual exception syndrome information
>>> + */
>>> + if (vcpu->arch.hcr_el2 & HCR_VSE)
>>> + write_sysreg(vcpu->arch.fault.vsesr_el2, vsesr_el2);
>>> +#endif
>>> /* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
>>> write_sysreg(1 << 15, hstr_el2);
>>> /*
>>> @@ -139,8 +146,14 @@ static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
>>> * the crucial bit is "On taking a vSError interrupt,
>>> * HCR_EL2.VSE is cleared to 0."
>>> */
>>> - if (vcpu->arch.hcr_el2 & HCR_VSE)
>>> + if (vcpu->arch.hcr_el2 & HCR_VSE) {
>>> vcpu->arch.hcr_el2 = read_sysreg(hcr_el2);
>>> +#ifdef CONFIG_HAS_RAS_EXTENSION
>>> + /* set vsesr_el2[24:0] with esr_el2[24:0] */
>>> + kvm_vcpu_set_vsesr(vcpu, read_sysreg_el2(esr)
>>> + & VSESR_ELx_IDS_ISS_MASK);
>>
>> What guarantees that ESR_EL2 still contains the latest exception? What
>> does it mean to store something that is the current EL2 exception
>> syndrome together with an SError that has already been injected?
>
> yes, thanks for the review, I will add a judgement condition for the "exit_code"
> if the "exit_code == ARM_EXCEPTION_EL1_SERROR" then set the vsesr_el2.
>
> for the aarch32, it only need set the "ExT, bit [12]" and AET, "bits [15:14]", other bit is RES0
>
>>
>> Also, is it correct to directly copy the ESR_EL2 bits into VSESR_EL2? My
> please see below spec description, it virtual SERROR syndrome from VSESR_EL2.
> -----
> Control returns to the OS, and the ESB instruction is re-executed.
> — The physical asynchronous SError interrupt has been cleared, so it is not taken again.
> — The PE sets VDISR_EL2.A to 1 and records the syndrome from VSESR_EL2 in VDISR_EL2.
> -----
Which doesn't say anything about directly using ESR_EL2 and propagating
it directly to the guest, specially when there is *already* an SError
pending (just in case you haven't noticed, this is the *exit* path, and
I can't see why you would overload VSESR_EL2 at at point).
>
>> own reading of the specification seem to imply that there is at least
>> differences when the guest is AArch32. Surely there would be some
>> processing here.
>
>
>
>>
>>> +#endif
>>> + }
>>>
>>> __deactivate_traps_arch()();
>>> write_sysreg(0, hstr_el2);
>>> diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
>>> index da6a8cfa54a0..08a13dfe28a8 100644
>>> --- a/arch/arm64/kvm/inject_fault.c
>>> +++ b/arch/arm64/kvm/inject_fault.c
>>> @@ -242,4 +242,14 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu)
>>> void kvm_inject_vabt(struct kvm_vcpu *vcpu)
>>> {
>>> vcpu_set_hcr(vcpu, vcpu_get_hcr(vcpu) | HCR_VSE);
>>> +#ifdef CONFIG_HAS_RAS_EXTENSION
>>> + /* If virtual System Error or Asynchronous Abort is set. set
>>> + * the virtual exception syndrome information
>>> + */
>>> + kvm_vcpu_set_vsesr(vcpu, ((kvm_vcpu_get_vsesr(vcpu)
>>> + & (~VSESR_ELx_IDS_ISS_MASK))
>>> + | (kvm_vcpu_get_hsr(vcpu)
>>> + & VSESR_ELx_IDS_ISS_MASK)));
>>
>> What is the rational for setting VSESR_EL2 with the EL1 syndrome
>> information? That doesn't make any sense to me.
> thanks, I set the VSESR_EL2 using the EL2 syndrome information, "kvm_vcpu_get_hsr"
> return the value of esr_el2, not EL1 syndrome information
Ah, good point. But that doesn't make it more valid. I still don't see
anything in the spec that supports this behaviour, and I still propose
that when RAS is enabled, the VSError injection is mediated by userspace.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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