On Thu, 10 Mar 2022 10:31:09 +0000
Janosch Frank <frankja@xxxxxxxxxxxxx> wrote:
> Sometimes dumping inside of a VM fails, is unavailable or doesn't
> yield the required data. For these occasions we dump the VM from the
> outside, writing memory and cpu data to a file.
>
> Up to now PV guests only supported dumping from the inside of the
> guest through dumpers like KDUMP. A PV guest can be dumped from the
> hypervisor but the data will be stale and / or encrypted.
>
> To get the actual state of the PV VM we need the help of the
> Ultravisor who safeguards the VM state. New UV calls have been added
> to initialize the dump, dump storage state data, dump cpu data and
> complete the dump process. We expose these calls in this patch via a
> new UV ioctl command.
>
> The sensitive parts of the dump data are encrypted, the dump key is
> derived from the Customer Communication Key (CCK). This ensures that
> only the owner of the VM who has the CCK can decrypt the dump data.
>
> The memory is dumped / read via a normal export call and a re-import
> after the dump initialization is not needed (no re-encryption with a
> dump key).
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> ---
> arch/s390/include/asm/kvm_host.h | 1 +
> arch/s390/kvm/kvm-s390.c | 137 +++++++++++++++++++++++++++++++
> arch/s390/kvm/kvm-s390.h | 2 +
> arch/s390/kvm/pv.c | 115 ++++++++++++++++++++++++++
> include/uapi/linux/kvm.h | 15 ++++
> 5 files changed, 270 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index a22c9266ea05..659bf4be6f04 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -921,6 +921,7 @@ struct kvm_s390_pv {
> u64 guest_len;
> unsigned long stor_base;
> void *stor_var;
> + bool dumping;
> };
>
> struct kvm_arch{
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index c388d08b9626..817e18c4244d 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -606,6 +606,26 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_S390_PROTECTED:
> r = is_prot_virt_host();
> break;
> + case KVM_CAP_S390_PROTECTED_DUMP: {
> + u64 pv_cmds_dump[] = {
> + BIT_UVC_CMD_DUMP_INIT,
> + BIT_UVC_CMD_DUMP_CONFIG_STOR_STATE,
> + BIT_UVC_CMD_DUMP_CONFIG_STOR_STATE,
you have this twice ^
> + BIT_UVC_CMD_DUMP_CPU,
> + };
> + int i;
> +
> + if (!is_prot_virt_host())
> + return 0;
> +
> + r = 1;
> + for (i = 0; i < ARRAY_SIZE(pv_cmds_dump); i++) {
> + if (!test_bit_inv(pv_cmds_dump[i],
> + (unsigned long *)&uv_info.inst_calls_list))
> + return 0;
> + }
> + break;
> + }
> default:
> r = 0;
> }
> @@ -2271,6 +2291,92 @@ static ssize_t kvm_s390_handle_pv_info(struct kvm_s390_pv_info *info)
> }
> }
>
> +static int kvm_s390_pv_dmp(struct kvm *kvm, struct kvm_pv_cmd *cmd,
I am all for shortening long words, but dmp -> dump is only one extra
byte
> + struct kvm_s390_pv_dmp dmp)
> +{
> + int r = -EINVAL;
> + void __user *result_buff = (void __user *)dmp.buff_addr;
> +
> + switch (dmp.subcmd) {
> + case KVM_PV_DUMP_INIT: {
> + if (kvm->arch.pv.dumping)
> + break;
> +
> + r = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
> + UVC_CMD_DUMP_INIT, &cmd->rc, &cmd->rrc);
> + KVM_UV_EVENT(kvm, 3, "PROTVIRT DUMP INIT: rc %x rrc %x",
> + cmd->rc, cmd->rrc);
> + if (!r)
> + kvm->arch.pv.dumping = true;
so at this point no guest CPUs should be running, right?
below you add a check to prevent guest CPUs from being dispatched if we
are in dump mode.
are there any checks to make sure all guest CPUs are stopped when
issuing this command? could a guest CPU be running while this command
is issued?
> + else
> + r = -EINVAL;
> + break;
> + }
> + case KVM_PV_DUMP_CONFIG_STOR_STATE: {
> + if (!kvm->arch.pv.dumping)
> + break;
> +
> + /*
> + * GADDR is an output parameter since we might stop
why uppercase?
> + * early. As dmp will be copied back in our caller, we
> + * don't need to do it ourselves.
> + */
> + r = kvm_s390_pv_dump_stor_state(kvm, result_buff, &dmp.gaddr, dmp.buff_len,
> + &cmd->rc, &cmd->rrc);
> + break;
> + }
> + case KVM_PV_DUMP_COMPLETE: {
> + struct uv_cb_dump_complete complete = {
> + .header.len = sizeof(complete),
> + .header.cmd = UVC_CMD_DUMP_COMPLETE,
> + .config_handle = kvm_s390_pv_get_handle(kvm),
> + };
> + u64 *compl_data;
> +
> + r = -EINVAL;
> + if (!kvm->arch.pv.dumping)
> + break;
> +
> + if (dmp.buff_len < uv_info.conf_dump_finalize_len)
> + break;
> +
> + /* Allocate dump area */
> + r = -ENOMEM;
> + compl_data = vzalloc(uv_info.conf_dump_finalize_len);
> + if (!compl_data)
> + break;
> + complete.dump_area_origin = (u64)compl_data;
> +
> + r = uv_call(0, (u64)&complete);
> + cmd->rc = complete.header.rc;
> + cmd->rrc = complete.header.rrc;
> + KVM_UV_EVENT(kvm, 3, "PROTVIRT DUMP COMPLETE: rc %x rrc %x",
> + complete.header.rc, complete.header.rrc);
> +
> + if (!r) {
> + /*
> + * kvm_s390_pv_dealloc_vm() will also (mem)set
> + * this to false on a reboot or other destroy
> + * operation for this vm.
> + */
> + kvm->arch.pv.dumping = false;
> + r = copy_to_user(result_buff, compl_data, uv_info.conf_dump_finalize_len);
> + if (r)
> + r = -EFAULT;
> + }
> + vfree(compl_data);
> + if (r > 0)
> + r = -EINVAL;
> + break;
> + }
> + default:
> + r = -ENOTTY;
> + break;
> + }
> +
> + return r;
> +}
> +
> static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
> {
> int r = 0;
> @@ -2447,6 +2553,28 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
> r = 0;
> break;
> }
> + case KVM_PV_DUMP: {
> + struct kvm_s390_pv_dmp dmp;
> +
> + r = -EINVAL;
> + if (!kvm_s390_pv_is_protected(kvm))
> + break;
> +
> + r = -EFAULT;
> + if (copy_from_user(&dmp, argp, sizeof(dmp)))
> + break;
> +
> + r = kvm_s390_pv_dmp(kvm, cmd, dmp);
> + if (r)
> + break;
> +
> + if (copy_to_user(argp, &dmp, sizeof(dmp))) {
> + r = -EFAULT;
> + break;
> + }
> +
> + break;
> + }
> default:
> r = -ENOTTY;
> }
> @@ -4542,6 +4670,15 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> struct kvm_run *kvm_run = vcpu->run;
> int rc;
>
> + /*
> + * Running a VM while dumping always has the potential to
> + * produce inconsistent dump data. But for PV vcpus a SIE
> + * entry while dumping could also lead to a validity which we
> + * absolutely want to avoid.
> + */
> + if (vcpu->kvm->arch.pv.dumping)
> + return -EINVAL;
> +
> if (kvm_run->immediate_exit)
> return -EINTR;
>
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 4ba8fc30d87a..324a23bf0678 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -250,6 +250,8 @@ int kvm_s390_pv_set_sec_parms(struct kvm *kvm, void *hdr, u64 length, u16 *rc,
> int kvm_s390_pv_unpack(struct kvm *kvm, unsigned long addr, unsigned long size,
> unsigned long tweak, u16 *rc, u16 *rrc);
> int kvm_s390_pv_set_cpu_state(struct kvm_vcpu *vcpu, u8 state);
> +int kvm_s390_pv_dump_stor_state(struct kvm *kvm, void __user *buff_user,
> + u64 *gaddr, u64 buff_user_len, u16 *rc, u16 *rrc);
>
> static inline u64 kvm_s390_pv_get_handle(struct kvm *kvm)
> {
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 7f7c0d6af2ce..2d42ec53a52e 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -303,3 +303,118 @@ int kvm_s390_pv_set_cpu_state(struct kvm_vcpu *vcpu, u8 state)
> return -EINVAL;
> return 0;
> }
> +
> +/* Size of the cache for the storage state dump data. 1MB for now */
> +#define DUMP_BUFF_LEN HPAGE_SIZE
> +
> +/*
> + * kvm_s390_pv_dump_stor_state
> + *
> + * @kvm: pointer to the guest's KVM struct
> + * @buff_user: Userspace pointer where we will write the results to
> + * @gaddr: Starting absolute guest address for which the storage state
> + * is requested. This value will be updated with the last
> + * address for which data was written when returning to
> + * userspace.
> + * @buff_user_len: Length of the buff_user buffer
> + * @rc: Pointer to where the uvcb return code is stored
> + * @rrc: Pointer to where the uvcb return reason code is stored
> + *
> + * Return:
> + * 0 on success
> + * -ENOMEM if allocating the cache fails
> + * -EINVAL if gaddr is not aligned to 1MB
> + * -EINVAL if buff_user_len is not aligned to uv_info.conf_dump_storage_state_len
> + * -EINVAL if the UV call fails, rc and rrc will be set in this case
> + * -EFAULT if copying the result to buff_user failed
> + */
> +int kvm_s390_pv_dump_stor_state(struct kvm *kvm, void __user *buff_user,
> + u64 *gaddr, u64 buff_user_len, u16 *rc, u16 *rrc)
> +{
> + struct uv_cb_dump_stor_state uvcb = {
> + .header.cmd = UVC_CMD_DUMP_CONF_STOR_STATE,
> + .header.len = sizeof(uvcb),
> + .config_handle = kvm->arch.pv.handle,
> + .gaddr = *gaddr,
> + .dump_area_origin = 0,
> + };
> + size_t buff_kvm_size;
> + size_t size_done = 0;
> + u8 *buff_kvm = NULL;
> + int cc, ret;
> +
> + ret = -EINVAL;
> + /* UV call processes 1MB guest storage chunks at a time */
> + if (*gaddr & ~HPAGE_MASK)
> + goto out;
so we only allow userspace to use starting addresses that are 1M
aligned...
> +
> + /*
> + * We provide the storage state for 1MB chunks of guest
> + * storage. The buffer will need to be aligned to
> + * conf_dump_storage_state_len so we don't end on a partial
> + * chunk.
> + */
> + if (!buff_user_len ||
> + buff_user_len & (uv_info.conf_dump_storage_state_len - 1))
> + goto out;
> +
> + /*
> + * Allocate a buffer from which we will later copy to the user process.
> + *
> + * We don't want userspace to dictate our buffer size so we limit it to DUMP_BUFF_LEN.
> + */
> + ret = -ENOMEM;
> + buff_kvm_size = buff_user_len <= DUMP_BUFF_LEN ? buff_user_len : DUMP_BUFF_LEN;
... and we allow the length to be less than 1M
meaning that userspace can request a small chunk, but won't be able to
continue, it will have to request the chunk again with a larger buffer
size if it wants to do any forward progess, is this correct?
> + buff_kvm = vzalloc(buff_kvm_size);
> + if (!buff_kvm)
> + goto out;
> +
> + ret = 0;
> + uvcb.dump_area_origin = (u64)buff_kvm;
> + /* We will loop until the user buffer is filled or an error occurs */
> + do {
> + /* Get a page of data */
> + cc = uv_call_sched(0, (u64)&uvcb);
> +
> + /* All or nothing */
> + if (cc) {
> + ret = -EINVAL;
> + break;
> + }
> +
> + size_done += uv_info.conf_dump_storage_state_len;
> + uvcb.dump_area_origin += uv_info.conf_dump_storage_state_len;
> + uvcb.gaddr += HPAGE_SIZE;
> + buff_user_len -= PAGE_SIZE;
shouldn't this be HPAGE_SIZE ^ ?
what happens if buff_user_len is > 1M but not 1M aligned?
> +
> + /* KVM Buffer full, time to copy to the process */
> + if (!buff_user_len ||
> + uvcb.dump_area_origin == (uintptr_t)buff_kvm + buff_kvm_size) {
can't you use size_done here ? ^
> +
> + if (copy_to_user(buff_user, buff_kvm,
> + uvcb.dump_area_origin - (uintptr_t)buff_kvm)) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + buff_user += size_done;
> + size_done = 0;
> + uvcb.dump_area_origin = (u64)buff_kvm;
> + }
> + } while (buff_user_len);
> +
> + /* Report back where we ended dumping */
> + *gaddr = uvcb.gaddr;
> +
> + /* Lets only log errors, we don't want to spam */
> +out:
> + if (ret)
> + KVM_UV_EVENT(kvm, 3,
> + "PROTVIRT DUMP STORAGE STATE: addr %llx ret %d, uvcb rc %x rrc %x",
> + uvcb.gaddr, ret, uvcb.header.rc, uvcb.header.rrc);
> + *rc = uvcb.header.rc;
> + *rrc = uvcb.header.rrc;
> + vfree(buff_kvm);
> +
> + return ret;
> +}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index eed2ae8397ae..6808ea0be648 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1643,6 +1643,20 @@ struct kvm_s390_pv_unp {
> __u64 tweak;
> };
>
> +enum pv_cmd_dmp_id {
> + KVM_PV_DUMP_INIT,
> + KVM_PV_DUMP_CONFIG_STOR_STATE,
> + KVM_PV_DUMP_COMPLETE,
> +};
> +
> +struct kvm_s390_pv_dmp {
> + __u64 subcmd;
> + __u64 buff_addr;
> + __u64 buff_len;
> + __u64 gaddr; /* For dump storage state */
> + __u64 reserved[4];
> +};
> +
> enum pv_cmd_info_id {
> KVM_PV_INFO_VM,
> KVM_PV_INFO_DUMP,
> @@ -1686,6 +1700,7 @@ enum pv_cmd_id {
> KVM_PV_PREP_RESET,
> KVM_PV_UNSHARE_ALL,
> KVM_PV_INFO,
> + KVM_PV_DUMP,
> };
>
> struct kvm_pv_cmd {
