Re: [PATCH RESEND v4 2/2] arm/arm64: KVM: Add KVM_GET/SET_VCPU_EVENTS

From: Marc Zyngier
Date: Sat Jun 09 2018 - 08:40:52 EST

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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@xxxxxxxxxx>
> ---
> 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).

> +
> + 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.

Thanks,

M.

--
Jazz is not dead, it just smell funny.

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