Re: [PATCH 6/9] kvm: s390: Add configuration dump functionality

Claudio Imbrenda
2022-05-09T19:12:59Z

On Thu, 28 Apr 2022 13:00:59 +0000
Janosch Frank <frankja@linux.ibm.com> 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@linux.ibm.com>
> ---
> arch/s390/include/asm/kvm_host.h | 1 +
> arch/s390/kvm/kvm-s390.c | 146 +++++++++++++++++++++++++++++++
> arch/s390/kvm/kvm-s390.h | 2 +
> arch/s390/kvm/pv.c | 115 ++++++++++++++++++++++++
> include/uapi/linux/kvm.h | 15 ++++
> 5 files changed, 279 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 766028d54a3e..a0fbe4820e0a 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -923,6 +923,7 @@ 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 e327a5b8ef78..8984e8db33b4 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_CPU,
> + BIT_UVC_CMD_DUMP_COMPLETE,
> + };
> + 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 +2291,101 @@ 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,
> + 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;
> +
> + /*
> + * Block SIE entry as concurrent dump UVCs could lead
> + * to validities.
> + */
> + kvm_s390_vcpu_block_all(kvm);
> +
> + 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;
> + else {
> + kvm_s390_vcpu_unblock_all(kvm);
> + 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
> + * 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;
> + kvm_s390_vcpu_unblock_all(kvm);
> + 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 +2562,28 @@ 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;
> }
> @@ -4564,6 +4701,15 @@ 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 497d52a83c78..2868dd0bba25 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 cc7c9599f43e..d1635ed50078 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -298,3 +298,118 @@ 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;
> +
> + /*
> + * 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))

why not use the IS_ALIGNED macro?

> + 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;
> + 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 */

are you getting a page or a block of size conf_dump_storage_state_len ?

> + 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;

same here ^ (should it be -= uv_info.conf_dump_storage_state_len ?)

> +
> + /* KVM Buffer full, time to copy to the process */
> + if (!buff_user_len ||
> + uvcb.dump_area_origin == (uintptr_t)buff_kvm +
> buff_kvm_size) { +

why not ... || size_done == DUMP_BUFF_LEN ?

> + if (copy_to_user(buff_user, buff_kvm,
> + uvcb.dump_area_origin -
> (uintptr_t)buff_kvm)) {

aren't you trying to copy size_done bytes?

> + 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 2eba89d7ec29..b34850907291 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1645,6 +1645,20 @@ 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,
> @@ -1688,6 +1702,7 @@ enum pv_cmd_id {
> KVM_PV_PREP_RESET,
> KVM_PV_UNSHARE_ALL,
> KVM_PV_INFO,
> + KVM_PV_DUMP,
> };
>
> struct kvm_pv_cmd {