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Subject: Re: [PATCH RESEND v4 2/2] arm/arm64: KVM: Add KVM_GET/SET_VCPU_EVENTS
To:     Marc Zyngier <marc.zyngier@arm.com>
CC:     <rkrcmar@redhat.com>, <corbet@lwn.net>, <christoffer.dall@arm.com>,
        <linux@armlinux.org.uk>, <catalin.marinas@arm.com>,
        <will.deacon@arm.com>, <kvm@vger.kernel.org>,
        <linux-doc@vger.kernel.org>, <james.morse@arm.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <linux-acpi@vger.kernel.org>
References: <1528487320-2873-1-git-send-email-gengdongjiu@huawei.com>
 <1528487320-2873-3-git-send-email-gengdongjiu@huawei.com>
 <86zi04875t.wl-marc.zyngier@arm.com>
From:   gengdongjiu <gengdongjiu@huawei.com>
Message-ID: <d404c732-64e5-43c1-eecf-cf63f91e33f9@huawei.com>
Date:   Tue, 12 Jun 2018 21:06:45 +0800
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Hi Marc
   thanks for the review.

On 2018/6/9 20:40, Marc Zyngier wrote:
> On Fri, 08 Jun 2018 20:48:40 +0100,
> Dongjiu Geng wrote:
>>
>> For the migrating VMs, user space may need to know the exception
>> state. For example, in the machine A, KVM make an SError pending,
>> when migrate to B, KVM also needs to pend an SError.
>>
>> This new IOCTL exports user-invisible states related to SError.
>> Together with appropriate user space changes, user space can get/set
>> the SError exception state to do migrate/snapshot/suspend.
>>
>> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
>> ---
>> change since v3:
>> 1. Fix the memset() issue in the kvm_arm_vcpu_get_events()
>>
>> change since v2:
>> 1. Add kvm_vcpu_events structure definition for arm platform to avoid the build errors.
>>
>> change since v1:
>> Address Marc's comments, thanks Marc's review
>> 1. serror_has_esr always true when ARM64_HAS_RAS_EXTN is set
>> 2. remove Spurious blank line in kvm_arm_vcpu_set_events()
>> 3. rename pend_guest_serror() to kvm_set_sei_esr()
>> 4. Make kvm_arm_vcpu_get_events() did all the work rather than having this split responsibility.
>> 5.  using sizeof(events) instead of sizeof(struct kvm_vcpu_events)
>>
>> this series patch is separated from https://www.spinics.net/lists/kvm/msg168917.html
>> The user space patch is here: https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg06965.html
>>
>> change since V12:
>> 1. change (vcpu->arch.hcr_el2 & HCR_VSE) to !!(vcpu->arch.hcr_el2 & HCR_VSE) in kvm_arm_vcpu_get_events()
>>
>> Change since V11:
>> Address James's comments, thanks James
>> 1. Align the struct of kvm_vcpu_events to 64 bytes
>> 2. Avoid exposing the stale ESR value in the kvm_arm_vcpu_get_events()
>> 3. Change variables 'injected' name to 'serror_pending' in the kvm_arm_vcpu_set_events()
>> 4. Change to sizeof(events) from sizeof(struct kvm_vcpu_events) in kvm_arch_vcpu_ioctl()
>>
>> Change since V10:
>> Address James's comments, thanks James
>> 1. Merge the helper function with the user.
>> 2. Move the ISS_MASK into pend_guest_serror() to clear top bits
>> 3. Make kvm_vcpu_events struct align to 4 bytes
>> 4. Add something check in the kvm_arm_vcpu_set_events()
>> 5. Check kvm_arm_vcpu_get/set_events()'s return value.
>> 6. Initialise kvm_vcpu_events to 0 so that padding transferred to user-space doesn't
>>    contain kernel stack.
>> ---
>>  Documentation/virtual/kvm/api.txt    | 31 ++++++++++++++++++++++++++++---
>>  arch/arm/include/asm/kvm_host.h      |  6 ++++++
>>  arch/arm/include/uapi/asm/kvm.h      | 12 ++++++++++++
>>  arch/arm/kvm/guest.c                 | 12 ++++++++++++
>>  arch/arm64/include/asm/kvm_emulate.h |  5 +++++
>>  arch/arm64/include/asm/kvm_host.h    |  7 +++++++
>>  arch/arm64/include/uapi/asm/kvm.h    | 13 +++++++++++++
>>  arch/arm64/kvm/guest.c               | 36 ++++++++++++++++++++++++++++++++++++
>>  arch/arm64/kvm/inject_fault.c        |  6 +++---
>>  arch/arm64/kvm/reset.c               |  1 +
>>  virt/kvm/arm/arm.c                   | 19 +++++++++++++++++++
>>  11 files changed, 142 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index fdac969..8896737 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -835,11 +835,13 @@ struct kvm_clock_data {
>>  
>>  Capability: KVM_CAP_VCPU_EVENTS
>>  Extended by: KVM_CAP_INTR_SHADOW
>> -Architectures: x86
>> +Architectures: x86, arm, arm64
>>  Type: vm ioctl
>>  Parameters: struct kvm_vcpu_event (out)
>>  Returns: 0 on success, -1 on error
>>  
>> +X86:
>> +
>>  Gets currently pending exceptions, interrupts, and NMIs as well as related
>>  states of the vcpu.
>>  
>> @@ -881,15 +883,32 @@ Only two fields are defined in the flags field:
>>  - KVM_VCPUEVENT_VALID_SMM may be set in the flags field to signal that
>>    smi contains a valid state.
>>  
>> +ARM, ARM64:
>> +
>> +Gets currently pending SError exceptions as well as related states of the vcpu.
>> +
>> +struct kvm_vcpu_events {
>> +	struct {
>> +		__u8 serror_pending;
>> +		__u8 serror_has_esr;
>> +		/* Align it to 8 bytes */
>> +		__u8 pad[6];
>> +		__u64 serror_esr;
>> +	} exception;
>> +	__u32 reserved[12];
>> +};
>> +
>>  4.32 KVM_SET_VCPU_EVENTS
>>  
>> -Capability: KVM_CAP_VCPU_EVENTS
>> +Capebility: KVM_CAP_VCPU_EVENTS
>>  Extended by: KVM_CAP_INTR_SHADOW
>> -Architectures: x86
>> +Architectures: x86, arm, arm64
>>  Type: vm ioctl
>>  Parameters: struct kvm_vcpu_event (in)
>>  Returns: 0 on success, -1 on error
>>  
>> +X86:
>> +
>>  Set pending exceptions, interrupts, and NMIs as well as related states of the
>>  vcpu.
>>  
>> @@ -910,6 +929,12 @@ shall be written into the VCPU.
>>  
>>  KVM_VCPUEVENT_VALID_SMM can only be set if KVM_CAP_X86_SMM is available.
>>  
>> +ARM, ARM64:
>> +
>> +Set pending SError exceptions as well as related states of the vcpu.
>> +
>> +See KVM_GET_VCPU_EVENTS for the data structure.
>> +
>>  
>>  4.33 KVM_GET_DEBUGREGS
>>  
>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> index c7c28c8..39f9901 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -213,6 +213,12 @@ unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
>>  int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
>>  int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
>>  int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
>> +int kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events);
>> +
>> +int kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events);
>> +
>>  unsigned long kvm_call_hyp(void *hypfn, ...);
>>  void force_vm_exit(const cpumask_t *mask);
>>  
>> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
>> index caae484..c3e6975 100644
>> --- a/arch/arm/include/uapi/asm/kvm.h
>> +++ b/arch/arm/include/uapi/asm/kvm.h
>> @@ -124,6 +124,18 @@ struct kvm_sync_regs {
>>  struct kvm_arch_memory_slot {
>>  };
>>  
>> +/* for KVM_GET/SET_VCPU_EVENTS */
>> +struct kvm_vcpu_events {
>> +	struct {
>> +		__u8 serror_pending;
>> +		__u8 serror_has_esr;
>> +		/* Align it to 8 bytes */
>> +		__u8 pad[6];
>> +		__u64 serror_esr;
>> +	} exception;
>> +	__u32 reserved[12];
>> +};
>> +
>>  /* If you need to interpret the index values, here is the key: */
>>  #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>>  #define KVM_REG_ARM_COPROC_SHIFT	16
>> diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
>> index a18f33e..c685f0e 100644
>> --- a/arch/arm/kvm/guest.c
>> +++ b/arch/arm/kvm/guest.c
>> @@ -261,6 +261,18 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
>>  	return -EINVAL;
>>  }
>>  
>> +int kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events)
>> +{
>> +	return -EINVAL;
>> +}
>> +
>> +int kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events)
>> +{
>> +	return -EINVAL;
>> +}
>> +
>>  int __attribute_const__ kvm_target_cpu(void)
>>  {
>>  	switch (read_cpuid_part()) {
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index 1dab3a9..18f61ff 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -81,6 +81,11 @@ static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
>>  	return (unsigned long *)&vcpu->arch.hcr_el2;
>>  }
>>  
>> +static inline unsigned long vcpu_get_vsesr(struct kvm_vcpu *vcpu)
>> +{
>> +	return vcpu->arch.vsesr_el2;
>> +}
>> +
>>  static inline void vcpu_set_vsesr(struct kvm_vcpu *vcpu, u64 vsesr)
>>  {
>>  	vcpu->arch.vsesr_el2 = vsesr;
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 469de8a..357304a 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -335,6 +335,11 @@ unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
>>  int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
>>  int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
>>  int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
>> +int kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events);
>> +
>> +int kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events);
>>  
>>  #define KVM_ARCH_WANT_MMU_NOTIFIER
>>  int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
>> @@ -363,6 +368,8 @@ void handle_exit_early(struct kvm_vcpu *vcpu, struct kvm_run *run,
>>  int kvm_perf_init(void);
>>  int kvm_perf_teardown(void);
>>  
>> +void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
>> +
>>  struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>>  
>>  void __kvm_set_tpidr_el2(u64 tpidr_el2);
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 04b3256..df4faee 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -39,6 +39,7 @@
>>  #define __KVM_HAVE_GUEST_DEBUG
>>  #define __KVM_HAVE_IRQ_LINE
>>  #define __KVM_HAVE_READONLY_MEM
>> +#define __KVM_HAVE_VCPU_EVENTS
>>  
>>  #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
>>  
>> @@ -153,6 +154,18 @@ struct kvm_sync_regs {
>>  struct kvm_arch_memory_slot {
>>  };
>>  
>> +/* for KVM_GET/SET_VCPU_EVENTS */
>> +struct kvm_vcpu_events {
>> +	struct {
>> +		__u8 serror_pending;
>> +		__u8 serror_has_esr;
>> +		/* Align it to 8 bytes */
>> +		__u8 pad[6];
>> +		__u64 serror_esr;
>> +	} exception;
>> +	__u32 reserved[12];
>> +};
>> +
>>  /* If you need to interpret the index values, here is the key: */
>>  #define KVM_REG_ARM_COPROC_MASK		0x000000000FFF0000
>>  #define KVM_REG_ARM_COPROC_SHIFT	16
>> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
>> index 56a0260..4426915 100644
>> --- a/arch/arm64/kvm/guest.c
>> +++ b/arch/arm64/kvm/guest.c
>> @@ -289,6 +289,42 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
>>  	return -EINVAL;
>>  }
>>  
>> +int kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events)
>> +{
>> +	memset(events, 0, sizeof(*events));
>> +
>> +	events->exception.serror_pending = !!(vcpu->arch.hcr_el2 & HCR_VSE);
>> +	events->exception.serror_has_esr =
>> +					cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
>> +
>> +	if (events->exception.serror_pending &&
>> +		events->exception.serror_has_esr)
>> +		events->exception.serror_esr = vcpu_get_vsesr(vcpu);
>> +	else
>> +		events->exception.serror_esr = 0;
> 
> Other than the alignment issues that Christoffer already commented on,
> you can perfectly remove the "else" clause altogether (we've just
> zeroed the whole structure).
yes, you are right. it should be moved, thanks for the pointing out.

> 
>> +
>> +	return 0;
>> +}
>> +
>> +int kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
>> +			struct kvm_vcpu_events *events)
>> +{
>> +	bool serror_pending = events->exception.serror_pending;
>> +	bool has_esr = events->exception.serror_has_esr;
>> +
>> +	if (serror_pending && has_esr) {
>> +		if (!cpus_have_const_cap(ARM64_HAS_RAS_EXTN))
>> +			return -EINVAL;
>> +
>> +		kvm_set_sei_esr(vcpu, events->exception.serror_esr);
>> +	} else if (serror_pending) {
>> +		kvm_inject_vabt(vcpu);
>> +	}
>> +
>> +	return 0;
> 
> There was an earlier request to check that all the padding is set to
> zero. I still think this makes sense.
previously I think it may be not needed to check that all the padding is set to
zero. so not added it. but now I consider it again, it should be make sense to check that.
so I will added them. thanks for the mention again.

> 
> Thanks,
> 
> 	M.
>