[PATCH v2 4/6] pseries/plpks: add HCALLs for PowerVM Key Wrapping Module
Srish Srinivasan
ssrish at linux.ibm.com
Tue Jan 6 16:06:28 AEDT 2026
Hi Mimi,
thanks for taking a look.
On 1/2/26 10:55 PM, Mimi Zohar wrote:
> Hi Srish,
>
> On Wed, 2025-12-17 at 22:55 +0530, Srish Srinivasan wrote:
>> The hypervisor generated wrapping key is an AES-GCM-256 symmetric key which
>> is stored in a non-volatile, secure, and encrypted storage called the Power
>> LPAR Platform KeyStore. It has policy based protections that prevent it
>> from being read out or exposed to the user.
>>
>> Implement H_PKS_GEN_KEY, H_PKS_WRAP_OBJECT, and H_PKS_UNWRAP_OBJECT HCALLs
>> to enable using the PowerVM Key Wrapping Module (PKWM) as a new trust
>> source for trusted keys. Disallow H_PKS_READ_OBJECT, H_PKS_SIGNED_UPDATE,
>> and H_PKS_WRITE_OBJECT for objects with the 'wrapping key' policy set.
>> Capture the availability status for the H_PKS_WRAP_OBJECT interface.
>>
>> Signed-off-by: Srish Srinivasan <ssrish at linux.ibm.com>
> scripts/checkpatch.pl --codespell caught a couple of typos. Please fix the
> typos here in in this patch and the one in v2 5/6.
Sure, I will fix them and send out v3.
Thanks for pointing these out.
>> ---
>> Documentation/arch/powerpc/papr_hcalls.rst | 43 +++
>> arch/powerpc/include/asm/plpks.h | 10 +
>> arch/powerpc/platforms/pseries/plpks.c | 345 ++++++++++++++++++++-
>> 3 files changed, 396 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/arch/powerpc/papr_hcalls.rst b/Documentation/arch/powerpc/papr_hcalls.rst
>> index 805e1cb9bab9..14e39f095a1c 100644
>> --- a/Documentation/arch/powerpc/papr_hcalls.rst
>> +++ b/Documentation/arch/powerpc/papr_hcalls.rst
>> @@ -300,6 +300,49 @@ H_HTM supports setup, configuration, control and dumping of Hardware Trace
>> Macro (HTM) function and its data. HTM buffer stores tracing data for functions
>> like core instruction, core LLAT and nest.
>>
>> +**H_PKS_GEN_KEY**
>> +
>> +| Input: authorization, objectlabel, objectlabellen, policy, out, outlen
>> +| Out: *Hypervisor Generated Key, or None when the wrapping key policy is set*
>> +| Return Value: *H_SUCCESS, H_Function, H_State, H_R_State, H_Parameter, H_P2,
>> + H_P3, H_P4, H_P5, H_P6, H_Authority, H_Nomem, H_Busy, H_Resource,
>> + H_Aborted*
>> +
>> +H_PKS_GEN_KEY is used to have the hypervisor generate a new random key.
>> +This key is stored as an object in the Power LPAR Platform KeyStore with
>> +the provided object label. With the wrapping key policy set the key is only
>> +visible to the hypervisor, while the key's label would still be visible to
>> +the user. Generation of wrapping keys is supported only for a key size of
>> +32 bytes.
>> +
>> +**H_PKS_WRAP_OBJECT**
>> +
>> +| Input: authorization, wrapkeylabel, wrapkeylabellen, objectwrapflags, in,
>> +| inlen, out, outlen, continue-token
>> +| Out: *continue-token, byte size of wrapped object, wrapped object*
>> +| Return Value: *H_SUCCESS, H_Function, H_State, H_R_State, H_Parameter, H_P2,
>> + H_P3, H_P4, H_P5, H_P6, H_P7, H_P8, H_P9, H_Authority, H_Invalid_Key,
>> + H_NOT_FOUND, H_Busy, H_LongBusy, H_Aborted*
>> +
>> +H_PKS_WRAP_OBJECT is used to wrap an object using a wrapping key stored in the
>> +Power LPAR Platform KeyStore and return the wrapped object to the caller. The
>> +caller provides a label to a wrapping key with the 'wrapping key' policy set,
>> +which must have been previously created with H_PKS_GEN_KEY. The provided object
>> +is then encrypted with the wrapping key and additional metadata and the result
>> +is returned to the caller.
>> +
>> +
>> +**H_PKS_UNWRAP_OBJECT**
>> +
>> +| Input: authorization, objectwrapflags, in, inlen, out, outlen, continue-token
>> +| Out: *continue-token, byte size of unwrapped object, unwrapped object*
>> +| Return Value: *H_SUCCESS, H_Function, H_State, H_R_State, H_Parameter, H_P2,
>> + H_P3, H_P4, H_P5, H_P6, H_P7, H_Authority, H_Unsupported, H_Bad_Data,
>> + H_NOT_FOUND, H_Invalid_Key, H_Busy, H_LongBusy, H_Aborted*
>> +
>> +H_PKS_UNWRAP_OBJECT is used to unwrap an object that was previously warapped with
>> +H_PKS_WRAP_OBJECT.
>> +
>> References
>> ==========
>> .. [1] "Power Architecture Platform Reference"
>> diff --git a/arch/powerpc/include/asm/plpks.h b/arch/powerpc/include/asm/plpks.h
>> index 8f034588fdf7..e87f90e40d4e 100644
>> --- a/arch/powerpc/include/asm/plpks.h
>> +++ b/arch/powerpc/include/asm/plpks.h
>> @@ -113,6 +113,16 @@ void plpks_early_init_devtree(void);
>> int plpks_populate_fdt(void *fdt);
>>
>> int plpks_config_create_softlink(struct kobject *from);
>> +
>> +bool plpks_wrapping_is_supported(void);
>> +
>> +int plpks_gen_wrapping_key(void);
>> +
>> +int plpks_wrap_object(u8 **input_buf, u32 input_len, u16 wrap_flags,
>> + u8 **output_buf, u32 *output_len);
>> +
>> +int plpks_unwrap_object(u8 **input_buf, u32 input_len,
>> + u8 **output_buf, u32 *output_len);
>> #else // CONFIG_PSERIES_PLPKS
>> static inline bool plpks_is_available(void) { return false; }
>> static inline u16 plpks_get_passwordlen(void) { BUILD_BUG(); }
>> diff --git a/arch/powerpc/platforms/pseries/plpks.c b/arch/powerpc/platforms/pseries/plpks.c
>> index 4a08f51537c8..2ec04908b057 100644
>> --- a/arch/powerpc/platforms/pseries/plpks.c
>> +++ b/arch/powerpc/platforms/pseries/plpks.c
>> @@ -9,6 +9,32 @@
>>
>> #define pr_fmt(fmt) "plpks: " fmt
>>
>> +#define PLPKS_WRAPKEY_COMPONENT "PLPKSWR"
>> +#define PLPKS_WRAPKEY_NAME "default-wrapping-key"
>> +
>> +/*
>> + * To 4K align the {input, output} buffers to the {UN}WRAP H_CALLs
>> + */
>> +#define PLPKS_WRAPPING_BUF_ALIGN 4096
>> +
>> +/*
>> + * To ensure the output buffer's length is at least 1024 bytes greater
>> + * than the input buffer's length during the WRAP H_CALL
>> + */
>> +#define PLPKS_WRAPPING_BUF_DIFF 1024
>> +
>> +#define PLPKS_WRAP_INTERFACE_BIT 3
>> +#define PLPKS_WRAPPING_KEY_LENGTH 32
>> +
>> +#define WRAPFLAG_BE_BIT_SET(be_bit) \
>> + BIT_ULL(63 - (be_bit))
>> +
>> +#define WRAPFLAG_BE_GENMASK(be_bit_hi, be_bit_lo) \
>> + GENMASK_ULL(63 - (be_bit_hi), 63 - (be_bit_lo))
>> +
>> +#define WRAPFLAG_BE_FIELD_PREP(be_bit_hi, be_bit_lo, val) \
>> + FIELD_PREP(WRAPFLAG_BE_GENMASK(be_bit_hi, be_bit_lo), (val))
>> +
>> #include <linux/delay.h>
>> #include <linux/errno.h>
>> #include <linux/io.h>
>> @@ -39,6 +65,7 @@ static u32 supportedpolicies;
>> static u32 maxlargeobjectsize;
>> static u64 signedupdatealgorithms;
>> static u64 wrappingfeatures;
>> +static bool wrapsupport;
>>
>> struct plpks_auth {
>> u8 version;
>> @@ -283,6 +310,7 @@ static int _plpks_get_config(void)
>> maxlargeobjectsize = be32_to_cpu(config->maxlargeobjectsize);
>> signedupdatealgorithms = be64_to_cpu(config->signedupdatealgorithms);
>> wrappingfeatures = be64_to_cpu(config->wrappingfeatures);
>> + wrapsupport = config->flags & PPC_BIT8(PLPKS_WRAP_INTERFACE_BIT);
>>
>> // Validate that the numbers we get back match the requirements of the spec
>> if (maxpwsize < 32) {
>> @@ -614,6 +642,9 @@ int plpks_signed_update_var(struct plpks_var *var, u64 flags)
>> if (!(var->policy & PLPKS_SIGNEDUPDATE))
>> return -EINVAL;
>>
>> + if (var->policy & PLPKS_WRAPPINGKEY)
>> + return -EINVAL;
>> +
>> // Signed updates need the component to be NULL.
>> if (var->component)
>> return -EINVAL;
>> @@ -696,6 +727,9 @@ int plpks_write_var(struct plpks_var var)
>> if (var.policy & PLPKS_SIGNEDUPDATE)
>> return -EINVAL;
>>
>> + if (var.policy & PLPKS_WRAPPINGKEY)
>> + return -EINVAL;
>> +
>> auth = construct_auth(PLPKS_OS_OWNER);
>> if (IS_ERR(auth))
>> return PTR_ERR(auth);
>> @@ -790,6 +824,9 @@ static int plpks_read_var(u8 consumer, struct plpks_var *var)
>> if (var->namelen > PLPKS_MAX_NAME_SIZE)
>> return -EINVAL;
>>
>> + if (var->policy & PLPKS_WRAPPINGKEY)
>> + return -EINVAL;
>> +
>> auth = construct_auth(consumer);
>> if (IS_ERR(auth))
>> return PTR_ERR(auth);
>> @@ -845,8 +882,312 @@ static int plpks_read_var(u8 consumer, struct plpks_var *var)
>> }
>>
>> /**
>> - * plpks_read_os_var() - Fetch the data for the specified variable that is
>> - * owned by the OS consumer.
>> + * plpks_wrapping_is_supported() - Get the H_PKS_WRAP_OBJECT interface
>> + * availability status for the LPAR.
>> + *
>> + * Successful execution of the H_PKS_GET_CONFIG HCALL during initialization
>> + * sets bit 3 of the flags variable in the PLPKS config structure if the
>> + * H_PKS_WRAP_OBJECT interface is supported.
>> + *
>> + * Returns: true if the H_PKS_WRAP_OBJECT interface is supported, false if not.
>> + */
>> +bool plpks_wrapping_is_supported(void)
>> +{
>> + return wrapsupport;
>> +}
>> +
>> +/**
>> + * plpks_gen_wrapping_key() - Generate a new random key with the 'wrapping key'
>> + * policy set.
>> + *
>> + * The H_PKS_GEN_KEY HCALL makes the hypervisor generate a new random key and
>> + * store the key in a PLPKS object with the provided object label. With the
>> + * 'wrapping key' policy set, only the label to the newly generated random key
>> + * would be visible to the user.
>> + *
>> + * Possible reasons for the returned errno values:
>> + *
>> + * -ENXIO if PLPKS is not supported
>> + * -EIO if PLPKS access is blocked due to the LPAR's state
>> + * if PLPKS modification is blocked due to the LPAR's state
>> + * if an error occurred while processing the request
>> + * -EINVAL if invalid authorization parameter
>> + * if invalid object label parameter
>> + * if invalid object label len parameter
>> + * if invalid or unsupported policy declaration
>> + * if invalid output buffer parameter
>> + * if invalid output buffer length parameter
>> + * -EPERM if access is denied
>> + * -ENOMEM if there is inadequate memory to perform this operation
>> + * -EBUSY if unable to handle the request
>> + * -EEXIST if the object label already exists
>> + *
>> + * Returns: On success 0 is returned, a negative errno if not.
>> + */
>> +int plpks_gen_wrapping_key(void)
>> +{
>> + unsigned long retbuf[PLPAR_HCALL_BUFSIZE] = { 0 };
>> + struct plpks_auth *auth;
>> + struct label *label;
>> + int rc = 0, pseries_status = 0;
>> + struct plpks_var var = {
>> + .name = PLPKS_WRAPKEY_NAME,
>> + .namelen = strlen(var.name),
>> + .policy = PLPKS_WRAPPINGKEY,
>> + .os = PLPKS_VAR_LINUX,
>> + .component = PLPKS_WRAPKEY_COMPONENT
>> + };
>> +
>> + auth = construct_auth(PLPKS_OS_OWNER);
>> + if (IS_ERR(auth))
>> + return PTR_ERR(auth);
>> +
>> + label = construct_label(var.component, var.os, var.name, var.namelen);
>> + if (IS_ERR(label)) {
>> + rc = PTR_ERR(label);
>> + goto out;
>> + }
>> +
>> + rc = plpar_hcall(H_PKS_GEN_KEY, retbuf,
>> + virt_to_phys(auth), virt_to_phys(label),
>> + label->size, var.policy,
>> + NULL, PLPKS_WRAPPING_KEY_LENGTH);
>> +
>> + if (!rc)
>> + rc = plpks_confirm_object_flushed(label, auth);
>> +
>> + pseries_status = rc;
>> + rc = pseries_status_to_err(rc);
>> +
>> + if (rc && rc != -EEXIST) {
>> + pr_err("H_PKS_GEN_KEY failed.");
>> + pr_err("pseries_status = %d, error code = %d", pseries_status,
>> + rc);
>> + } else {
>> + rc = 0;
>> + }
>> +
>> + kfree(label);
>> +out:
>> + kfree(auth);
>> + return rc;
>> +}
>> +EXPORT_SYMBOL_GPL(plpks_gen_wrapping_key);
>> +
>> +/**
>> + * plpks_wrap_object() - Wrap an object using the default wrapping key stored in
>> + * the PLPKS.
>> + * @input_buf: buffer containing the data to be wrapped
>> + * @input_len: length of the input buffer
>> + * @wrap_flags: object wrapping flags
>> + * @output_buf: buffer to store the wrapped data
>> + * @output_len: length of the output buffer
>> + *
>> + * The H_PKS_WRAP_OBJECT HCALL wraps an object using a wrapping key stored in
>> + * the PLPKS and returns the wrapped object to the caller. The caller provides a
>> + * label to the wrapping key with the 'wrapping key' policy set that must have
>> + * been previously created with the H_PKS_GEN_KEY HCALL. The provided object is
>> + * then encrypted with the wrapping key and additional metadata and the result
>> + * is returned to the user. The metadata includes the wrapping algorithm and the
>> + * wrapping key name so those parameters are not required during unwrap.
>> + *
>> + * Possible reasons for the returned errno values:
>> + *
>> + * -ENXIO if PLPKS is not supported
>> + * -EIO if PLPKS access is blocked due to the LPAR's state
>> + * if PLPKS modification is blocked due to the LPAR's state
>> + * if an error occurred while processing the request
>> + * -EINVAL if invalid authorization parameter
>> + * if invalid wraping key label parameter
> -> wrapping
Noted.
Will fix this.
>
>> + * if invalid wrapping key label length parameter
>> + * if invalid or unsupported object wrapping flags
>> + * if invalid inut buffer parameter
> -> input
Noted.
Will fix this.
>> + * if invalid input buffer length parameter
>> + * if invalid output buffer parameter
>> + * if invalid output buffer length parameter
>> + * if invalid continue token parameter
>> + * if the wrapping key is not compatible with the wrapping
>> + * algorithm
>> + * -EPERM if access is denied
>> + * -ENOENT if the requested wrapping key was not found
>> + * -EBUSY if unable to handle the request or long running operation
>> + * initiated, retry later.
>> + *
>> + * Returns: On success 0 is returned, a negative errno if not.
>> + */
>> +int plpks_wrap_object(u8 **input_buf, u32 input_len, u16 wrap_flags,
>> + u8 **output_buf, u32 *output_len)
>> +{
>> + unsigned long retbuf[PLPAR_HCALL9_BUFSIZE] = { 0 };
>> + struct plpks_auth *auth;
>> + struct label *label;
>> + u64 continuetoken = 0;
>> + u64 objwrapflags = 0;
>> + int rc = 0, pseries_status = 0;
>> + bool sb_audit_or_enforce_bit = wrap_flags & BIT(0);
>> + bool sb_enforce_bit = wrap_flags & BIT(1);
>> + struct plpks_var var = {
>> + .name = PLPKS_WRAPKEY_NAME,
>> + .namelen = strlen(var.name),
>> + .os = PLPKS_VAR_LINUX,
>> + .component = PLPKS_WRAPKEY_COMPONENT
>> + };
>> +
>> + auth = construct_auth(PLPKS_OS_OWNER);
>> + if (IS_ERR(auth))
>> + return PTR_ERR(auth);
>> +
>> + label = construct_label(var.component, var.os, var.name, var.namelen);
>> + if (IS_ERR(label)) {
>> + rc = PTR_ERR(label);
>> + goto out;
>> + }
>> +
>> + /* Set the consumer password requirement bit. A must have. */
>> + objwrapflags |= WRAPFLAG_BE_BIT_SET(3);
>> +
>> + /* Set the wrapping algorithm bit. Just one algorithm option for now */
>> + objwrapflags |= WRAPFLAG_BE_FIELD_PREP(60, 63, 0x1);
>> +
>> + if (sb_audit_or_enforce_bit & sb_enforce_bit) {
>> + pr_err("Cannot set both audit/enforce and enforce bits.");
>> + rc = -EINVAL;
>> + goto out_free_label;
>> + } else if (sb_audit_or_enforce_bit) {
>> + objwrapflags |= WRAPFLAG_BE_BIT_SET(1);
>> + } else if (sb_enforce_bit) {
>> + objwrapflags |= WRAPFLAG_BE_BIT_SET(2);
>> + }
>> +
>> + *output_len = input_len + PLPKS_WRAPPING_BUF_DIFF;
>> +
>> + *output_buf = kzalloc(ALIGN(*output_len, PLPKS_WRAPPING_BUF_ALIGN),
>> + GFP_KERNEL);
>> + if (!(*output_buf)) {
>> + pr_err("Output buffer allocation failed. Returning -ENOMEM.");
>> + rc = -ENOMEM;
>> + goto out_free_label;
>> + }
>> +
>> + do {
>> + rc = plpar_hcall9(H_PKS_WRAP_OBJECT, retbuf,
>> + virt_to_phys(auth), virt_to_phys(label),
>> + label->size, objwrapflags,
>> + virt_to_phys(*input_buf), input_len,
>> + virt_to_phys(*output_buf), *output_len,
>> + continuetoken);
>> +
>> + continuetoken = retbuf[0];
>> + pseries_status = rc;
>> + rc = pseries_status_to_err(rc);
>> + } while (rc == -EBUSY);
>> +
>> + if (rc) {
>> + pr_err("H_PKS_WRAP_OBJECT failed.");
>> + pr_err("pseries_status = %d, return code = %d", pseries_status,
>> + rc);
>> + kfree(*output_buf);
>> + *output_buf = NULL;
>> + } else {
>> + *output_len = retbuf[1];
>> + }
>> +
>> +out_free_label:
>> + kfree(label);
>> +out:
>> + kfree(auth);
>> + return rc;
>> +}
>> +EXPORT_SYMBOL_GPL(plpks_wrap_object);
>> +
>> +/**
>> + * plpks_unwrap_object() - Unwrap an object using the default wrapping key
>> + * stored in the PLPKS.
>> + * @input_buf: buffer containing the data to be unwrapped
>> + * @input_len: length of the input buffer
>> + * @output_buf: buffer to store the unwrapped data
>> + * @output_len: length of the output buffer
>> + *
>> + * The H_PKS_UNWRAP_OBJECT HCALL unwraps an object that was previously wrapped
>> + * using the H_PKS_WRAP_OBJECT HCALL.
>> + *
>> + * Possible reasons for the returned errno values:
>> + *
>> + * -ENXIO if PLPKS is not supported
>> + * -EIO if PLPKS access is blocked due to the LPAR's state
>> + * if PLPKS modification is blocked due to the LPAR's state
>> + * if an error occurred while processing the request
>> + * -EINVAL if invalid authorization parameter
>> + * if invalid or unsupported object unwrapping flags
>> + * if invalid inut buffer parameter
> -> input
Noted.
Will fix this.
>
>> + * if invalid input buffer length parameter
>> + * if invalid output buffer parameter
>> + * if invalid output buffer length parameter
>> + * if invalid continue token parameter
>> + * if the wrapping key is not compatible with the wrapping
>> + * algorithm
>> + * if the wrapped object's format is not supported
>> + * if the wrapped object is invalid
>> + * -EPERM if access is denied
>> + * -ENOENT if the wrapping key for the provided object was not found
>> + * -EBUSY if unable to handle the request or long running operation
>> + * initiated, retry later.
>> + *
>> + * Returns: On success 0 is returned, a negative errno if not.
>> + */
>> +int plpks_unwrap_object(u8 **input_buf, u32 input_len, u8 **output_buf,
>> + u32 *output_len)
>> +{
>> + unsigned long retbuf[PLPAR_HCALL9_BUFSIZE] = { 0 };
>> + struct plpks_auth *auth;
>> + u64 continuetoken = 0;
>> + u64 objwrapflags = 0;
>> + int rc = 0, pseries_status = 0;
>> +
>> + auth = construct_auth(PLPKS_OS_OWNER);
>> + if (IS_ERR(auth))
>> + return PTR_ERR(auth);
>> +
>> + *output_len = input_len - PLPKS_WRAPPING_BUF_DIFF;
>> + *output_buf = kzalloc(ALIGN(*output_len, PLPKS_WRAPPING_BUF_ALIGN),
>> + GFP_KERNEL);
>> + if (!(*output_buf)) {
>> + pr_err("Output buffer allocation failed. Returning -ENOMEM.");
>> + rc = -ENOMEM;
>> + goto out;
>> + }
>> +
>> + do {
>> + rc = plpar_hcall9(H_PKS_UNWRAP_OBJECT, retbuf,
>> + virt_to_phys(auth), objwrapflags,
>> + virt_to_phys(*input_buf), input_len,
>> + virt_to_phys(*output_buf), *output_len,
>> + continuetoken);
>> +
>> + continuetoken = retbuf[0];
>> + pseries_status = rc;
>> + rc = pseries_status_to_err(rc);
>> + } while (rc == -EBUSY);
>> +
>> + if (rc) {
>> + pr_err("H_PKS_UNWRAP_OBJECT failed.");
>> + pr_err("pseries_status = %d, return code = %d", pseries_status,
>> + rc);
>> + kfree(*output_buf);
>> + *output_buf = NULL;
>> + } else {
>> + *output_len = retbuf[1];
>> + }
>> +
>> +out:
>> + kfree(auth);
>> + return rc;
>> +}
>> +EXPORT_SYMBOL_GPL(plpks_unwrap_object);
>> +
>> +/**
>> + * plpks_read_os_var() - Fetch the data for the specified variable that is owned
>> + * by the OS consumer.
>> * @var: variable to be read from the PLPKS
>> *
>> * The consumer or the owner of the object is the os kernel. The
Thanks,
Srish.
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