Message-ID: <20170703083903.GE4066@cbox>
Date:   Mon, 3 Jul 2017 10:39:03 +0200
From:   Christoffer Dall <cdall@...aro.org>
To:     Dongjiu Geng <gengdongjiu@...wei.com>
Cc:     marc.zyngier@....com, james.morse@....com,
        christoffer.dall@...aro.org, kvmarm@...ts.cs.columbia.edu,
        wuquanming@...wei.com, huangshaoyu@...wei.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, rkrcmar@...hat.com,
        corbet@....net, catalin.marinas@....com, linux@...linux.org.uk,
        will.deacon@....com, suzuki.poulose@....com, huhuajun@...wei.com
Subject: Re: [PATCH v4 3/3] arm64: kvm: inject SError with user space
 specified syndrome

Hi Dongjiu,

On Mon, Jun 26, 2017 at 08:46:39PM +0800, Dongjiu Geng wrote:
> when SError happen, kvm notifies user space to record the CPER,
> user space specifies and passes the contents of ESR_EL1 on taking
> a virtual SError interrupt to KVM, KVM enables virtual system
> error or asynchronous abort with this specifies syndrome. This
> patch modify the world-switch to restore VSESR_EL2, VSESR_EL2
> saves the virtual SError syndrome, it becomes the ESR_EL1 value when
> HCR_EL2.VSE injects an SError. This register is added by the
> RAS Extensions.

This commit message is confusing and doesn't help me understand the
patch.

I think this patch is trying to do too many things.  I suggest you split
the patch into (at least) one patch that captures exception information
from the world-switch path, one patch that deals with the new exit
reason, and finally a patch with the new ioctl.  That way you can write
a commit message for each patch describing first what the patch does,
and then why this is a good idea.

Neverthess, I added some random comments below.

> 
> Changes since v3:
> (1) Move restore VSESR_EL2 value logic to a helper method
> (2) In the world-switch, not save VSESR_EL2, because no one cares the
>     old VSESR_EL2 value
> (3) Add a new KVM_ARM_SEI ioctl to set the VSESR_EL2 value and pend
>     a virtual system error
> 
> Signed-off-by: Dongjiu Geng <gengdongjiu@...wei.com>
> Signed-off-by: Quanming Wu <wuquanming@...wei.com>
> ---
>  Documentation/virtual/kvm/api.txt    | 10 ++++++++++
>  arch/arm/include/asm/kvm_host.h      |  1 +
>  arch/arm/kvm/arm.c                   |  7 +++++++
>  arch/arm/kvm/guest.c                 |  5 +++++
>  arch/arm64/include/asm/esr.h         |  2 ++
>  arch/arm64/include/asm/kvm_emulate.h | 10 ++++++++++
>  arch/arm64/include/asm/kvm_host.h    |  2 ++
>  arch/arm64/include/asm/sysreg.h      |  3 +++
>  arch/arm64/kvm/guest.c               | 14 ++++++++++++++
>  arch/arm64/kvm/handle_exit.c         | 25 +++++++++++++++++++------
>  arch/arm64/kvm/hyp/switch.c          | 14 ++++++++++++++
>  include/uapi/linux/kvm.h             |  8 ++++++++
>  12 files changed, 95 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 3c248f7..852ac55 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3377,6 +3377,16 @@ struct kvm_ppc_resize_hpt {
>  	__u32 pad;
>  };
>  
> +4.104 KVM_ARM_SEI
> +
> +Capability: KVM_EXIT_SERROR_INTR
> +Architectures: arm/arm64
> +Type: vcpu ioctl
> +Parameters: u64 (syndrome)
> +Returns: 0 in case of success
> +
> +Pend an virtual system error or asynchronous abort with user space specified.
> +

I don't understand enough about what this ioctl does by just reading
this text.  Did you mean to say something like "Record that userspace
wishes to inject a pending virtual system error to the VCPU.  Next time
the VCPU is run, th

>  5. The kvm_run structure
>  ------------------------
>  
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 31ee468..566292a 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -244,6 +244,7 @@ int kvm_arm_coproc_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *);
>  
>  int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>  		int exception_index);
> +int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome);
>  
>  static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
>  				       unsigned long hyp_stack_ptr,
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 96dba7c..583294f 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -987,6 +987,13 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>  			return -EFAULT;
>  		return kvm_arm_vcpu_has_attr(vcpu, &attr);
>  	}
> +	case KVM_ARM_SEI: {
> +		u64 syndrome;
> +
> +		if (copy_from_user(&syndrome, argp, sizeof(syndrome)))
> +			return -EFAULT;
> +		return kvm_vcpu_ioctl_sei(vcpu, &syndrome);
> +	}
>  	default:
>  		return -EINVAL;
>  	}
> diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
> index fa6182a..72505bf 100644
> --- a/arch/arm/kvm/guest.c
> +++ b/arch/arm/kvm/guest.c
> @@ -248,6 +248,11 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
>  	return -EINVAL;
>  }
>  
> +int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome)
> +{
> +	return 0;
> +}
> +
>  int __attribute_const__ kvm_target_cpu(void)
>  {
>  	switch (read_cpuid_part()) {
> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
> index 22f9c90..d009c99 100644
> --- a/arch/arm64/include/asm/esr.h
> +++ b/arch/arm64/include/asm/esr.h
> @@ -127,6 +127,8 @@
>  #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 */
>  
>  /* BRK instruction trap from AArch64 state */
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 5f64ab2..93dc3d1 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -155,6 +155,16 @@ static inline u32 kvm_vcpu_get_hsr(const struct kvm_vcpu *vcpu)
>  	return vcpu->arch.fault.esr_el2;
>  }
>  
> +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;
> +}
> +
>  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 e7705e7..b6242fb 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -86,6 +86,7 @@ struct kvm_vcpu_fault_info {
>  	u32 esr_el2;		/* Hyp Syndrom Register */
>  	u64 far_el2;		/* Hyp Fault Address Register */
>  	u64 hpfar_el2;		/* Hyp IPA Fault Address Register */
> +	u32 vsesr_el2;		/* Virtual SError Exception Syndrome Register */
>  };
>  
>  /*
> @@ -385,6 +386,7 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
>  			       struct kvm_device_attr *attr);
>  int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
>  			       struct kvm_device_attr *attr);
> +int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome);
>  
>  static inline void __cpu_init_stage2(void)
>  {
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 32964c7..3af6907 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -125,6 +125,9 @@
>  #define REG_PSTATE_PAN_IMM		sys_reg(0, 0, 4, 0, 4)
>  #define REG_PSTATE_UAO_IMM		sys_reg(0, 0, 4, 0, 3)
>  
> +/* virtual SError exception syndrome register in armv8.2 */
> +#define REG_VSESR_EL2			sys_reg(3, 4, 5, 2, 3)
> +
>  #define SET_PSTATE_PAN(x) __emit_inst(0xd5000000 | REG_PSTATE_PAN_IMM |	\
>  				      (!!x)<<8 | 0x1f)
>  #define SET_PSTATE_UAO(x) __emit_inst(0xd5000000 | REG_PSTATE_UAO_IMM |	\
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index b37446a..21c20b0 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -277,6 +277,20 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
>  	return -EINVAL;
>  }
>  
> +int kvm_vcpu_ioctl_sei(struct kvm_vcpu *vcpu, u64 *syndrome)
> +{
> +	u64 reg = *syndrome;
> +
> +	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) && reg)
> +		/* set vsesr_el2[24:0] with value that user space specified */
> +		kvm_vcpu_set_vsesr(vcpu, reg & VSESR_ELx_IDS_ISS_MASK);

Are you really supposed to fail silently here if trying to do this on a
system that doesn't have RAS ?

Why can you not set reg to 0 here?  That doesn't seem to be documented
anywhere, and shouldn't the function return -EINVAL in this case?

Also, if you do this, but don't run the VCPU, then migrate the VM, and
run the VCPU on the new destination, isn't this information lost?


> +
> +	/* inject virtual system Error or asynchronous abort */
> +	kvm_inject_vabt(vcpu);
> +
> +	return 0;
> +}
> +
>  int __attribute_const__ kvm_target_cpu(void)
>  {
>  	unsigned long implementor = read_cpuid_implementor();
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index c89d83a..23c02c2 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -180,7 +180,11 @@ static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
>  
>  static int kvm_handle_guest_sei(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  {
> -	unsigned long fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
> +	unsigned long hva, fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
> +	struct kvm_memory_slot *memslot;
> +	int hsr, ret = 1;
> +	bool writable;
> +	gfn_t gfn;
>  
>  	if (handle_guest_sei((unsigned long)fault_ipa,
>  				kvm_vcpu_get_hsr(vcpu))) {
> @@ -190,9 +194,20 @@ static int kvm_handle_guest_sei(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  				(unsigned long)kvm_vcpu_get_hsr(vcpu));
>  
>  		kvm_inject_vabt(vcpu);
> +	} else {
> +		hsr = kvm_vcpu_get_hsr(vcpu);
> +
> +		gfn = fault_ipa >> PAGE_SHIFT;
> +		memslot = gfn_to_memslot(vcpu->kvm, gfn);
> +		hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);
> +
> +		run->exit_reason = KVM_EXIT_SERROR_INTR;
> +		run->serror_intr.syndrome_info = hsr;
> +		run->serror_intr.address = hva;
> +		ret = 0;
>  	}
>  
> -	return 0;
> +	return ret;
>  }
>  
>  /*
> @@ -218,8 +233,7 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>  			*vcpu_pc(vcpu) -= adj;
>  		}
>  
> -		kvm_handle_guest_sei(vcpu, run);
> -		return 1;
> +		return kvm_handle_guest_sei(vcpu, run);
>  	}
>  
>  	exception_index = ARM_EXCEPTION_CODE(exception_index);
> @@ -228,8 +242,7 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>  	case ARM_EXCEPTION_IRQ:
>  		return 1;
>  	case ARM_EXCEPTION_EL1_SERROR:
> -		kvm_handle_guest_sei(vcpu, run);
> -		return 1;
> +		return kvm_handle_guest_sei(vcpu, run);
>  	case ARM_EXCEPTION_TRAP:
>  		/*
>  		 * See ARM ARM B1.14.1: "Hyp traps on instructions
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index aede165..6d17c97 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -67,6 +67,13 @@ static hyp_alternate_select(__activate_traps_arch,
>  			    __activate_traps_nvhe, __activate_traps_vhe,
>  			    ARM64_HAS_VIRT_HOST_EXTN);
>  
> +static void __hyp_text __sysreg_set_vsesr(struct kvm_vcpu *vcpu)
> +{
> +	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) &&
> +			(vcpu->arch.hcr_el2 & HCR_VSE))
> +		write_sysreg_s(vcpu->arch.fault.vsesr_el2, REG_VSESR_EL2);
> +}
> +
>  static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>  {
>  	u64 val;
> @@ -86,6 +93,13 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>  		isb();
>  	}
>  	write_sysreg(val, hcr_el2);
> +
> +	/*
> +	 * If the virtual SError interrupt is taken to EL1 using AArch64,
> +	 * then VSESR_EL2 provides the syndrome value reported in ESR_EL1.
> +	 */
> +	__sysreg_set_vsesr(vcpu);
> +
>  	/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
>  	write_sysreg(1 << 15, hstr_el2);
>  	/*
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 27fe556..ab91fe3 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -205,6 +205,7 @@ struct kvm_hyperv_exit {
>  #define KVM_EXIT_S390_STSI        25
>  #define KVM_EXIT_IOAPIC_EOI       26
>  #define KVM_EXIT_HYPERV           27
> +#define KVM_EXIT_SERROR_INTR      28
>  
>  /* For KVM_EXIT_INTERNAL_ERROR */
>  /* Emulate instruction failed. */
> @@ -360,6 +361,11 @@ struct kvm_run {
>  		struct {
>  			__u8 vector;
>  		} eoi;
> +		/* KVM_EXIT_SERROR_INTR */
> +		struct {
> +			__u32 syndrome_info;
> +			__u64 address;
> +		} serror_intr;
>  		/* KVM_EXIT_HYPERV */
>  		struct kvm_hyperv_exit hyperv;
>  		/* Fix the size of the union. */
> @@ -1301,6 +1307,8 @@ struct kvm_s390_ucas_mapping {
>  #define KVM_S390_GET_IRQ_STATE	  _IOW(KVMIO, 0xb6, struct kvm_s390_irq_state)
>  /* Available with KVM_CAP_X86_SMM */
>  #define KVM_SMI                   _IO(KVMIO,   0xb7)
> +/* Available with KVM_EXIT_SERROR_INTR */
> +#define KVM_ARM_SEI               _IO(KVMIO,   0xb8)
>  
>  #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
>  #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
> -- 
> 2.10.1
> 

Thanks,
-Christoffer

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