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virt: arm-cca-guest: use migrate_disable() for attestation token requests

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The RSI attestation token init and continue calls must be issued from
the same CPU. arm_cca_report_new() currently snapshots the CPU number
and uses smp_call_function_single() to issue those calls on that CPU.

With CONFIG_DEBUG_PREEMPT=y, the smp_processor_id() call used for the
snapshot triggers a debug splat [0] because it runs in preemptible
context. The snapshot does not pin the task to that CPU; it is only used
to choose the target CPU for smp_call_function_single(), which can fail
if that CPU is no longer available.

Use migrate_disable() and issue the token init and continue operations
directly, without the smp_call_function_single() callbacks. This keeps
the token request sequence on the same CPU while preserving a sleepable
context for the GFP_KERNEL allocations needed after the init call.

[0]
 BUG: using smp_processor_id() in preemptible [00000000] code: cca-workload-at/264
 caller is debug_smp_processor_id+0x20/0x30
 CPU: 0 UID: 0 PID: 264 Comm: cca-workload-at Not tainted 7.1.0-rc1-00044-g55542ab273f2 #80 PREEMPT(lazy)
 Hardware name: linux,dummy-virt (DT)
 Call trace:
  [...]
  check_preemption_disabled+0xd8/0xf8
  debug_smp_processor_id+0x20/0x30
  arm_cca_report_new+0x48/0x278
  tsm_report_read+0x154/0x1f8
  tsm_report_outblob_read+0x20/0x38
  configfs_bin_read_iter+0x118/0x208
  vfs_read+0x220/0x318
  [...]

Fixes: 7999edc484 ("virt: arm-cca-guest: TSM_REPORT support for realms")
Signed-off-by: Kohei Enju <enju.kohei@fujitsu.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Kohei Enju
2026-06-12 20:09:21 +09:00
committed by Will Deacon
parent a13c140cc2
commit 24f55f511b
1 changed files with 36 additions and 61 deletions
Download Patch File Download Diff File Expand all files Collapse all files

97
drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
View File

@@ -16,54 +16,38 @@
/**
* struct arm_cca_token_info - a descriptor for the token buffer.
* @challenge: Pointer to the challenge data
* @challenge_size: Size of the challenge data
* @granule: PA of the granule to which the token will be written
* @offset: Offset within granule to start of buffer in bytes
* @result: result of rsi_attestation_token_continue operation
*/
struct arm_cca_token_info {
void *challenge;
unsigned long challenge_size;
phys_addr_t granule;
unsigned long offset;
unsigned long result;
};
static void arm_cca_attestation_init(void *param)
{
struct arm_cca_token_info *info;
info = (struct arm_cca_token_info *)param;
info->result = rsi_attestation_token_init(info->challenge,
info->challenge_size);
}
/**
* arm_cca_attestation_continue - Retrieve the attestation token data.
*
* @param: pointer to the arm_cca_token_info
* @info: pointer to the arm_cca_token_info
*
* Attestation token generation is a long running operation and therefore
* the token data may not be retrieved in a single call. Moreover, the
* token retrieval operation must be requested on the same CPU on which the
* attestation token generation was initialised.
* This helper function is therefore scheduled on the same CPU multiple
* This helper function must therefore be executed on the same CPU multiple
* times until the entire token data is retrieved.
*/
static void arm_cca_attestation_continue(void *param)
static unsigned long
arm_cca_attestation_continue(struct arm_cca_token_info *info)
{
unsigned long ret;
unsigned long len;
unsigned long size;
struct arm_cca_token_info *info;
info = (struct arm_cca_token_info *)param;
size = RSI_GRANULE_SIZE - info->offset;
info->result = rsi_attestation_token_continue(info->granule,
info->offset, size, &len);
ret = rsi_attestation_token_continue(info->granule, info->offset, size,
&len);
info->offset += len;
return ret;
}
/**
@@ -74,8 +58,8 @@ static void arm_cca_attestation_continue(void *param)
*
* Initialise the attestation token generation using the challenge data
* passed in the TSM descriptor. Allocate memory for the attestation token
* and schedule calls to retrieve the attestation token on the same CPU
* on which the attestation token generation was initialised.
* and retrieve the attestation token on the same CPU on which the
* attestation token generation was initialised.
*
* The challenge data must be at least 32 bytes and no more than 64 bytes. If
* less than 64 bytes are provided it will be zero padded to 64 bytes.
@@ -85,12 +69,11 @@ static void arm_cca_attestation_continue(void *param)
* * %-EINVAL - A parameter was not valid.
* * %-ENOMEM - Out of memory.
* * %-EFAULT - Failed to get IPA for memory page(s).
* * A negative status code as returned by smp_call_function_single().
*/
static int arm_cca_report_new(struct tsm_report *report, void *data)
{
int ret;
int cpu;
int ret = 0;
unsigned long rsi_result;
long max_size;
unsigned long token_size = 0;
struct arm_cca_token_info info;
@@ -103,37 +86,33 @@ static int arm_cca_report_new(struct tsm_report *report, void *data)
/*
* The attestation token 'init' and 'continue' calls must be
* performed on the same CPU. smp_call_function_single() is used
* instead of simply calling get_cpu() because of the need to
* allocate outblob based on the returned value from the 'init'
* call and that cannot be done in an atomic context.
* performed on the same CPU, so disable CPU migration around
* those operations.
*/
cpu = smp_processor_id();
migrate_disable();
info.challenge = desc->inblob;
info.challenge_size = desc->inblob_len;
ret = smp_call_function_single(cpu, arm_cca_attestation_init,
&info, true);
if (ret)
return ret;
max_size = info.result;
if (max_size <= 0)
return -EINVAL;
max_size = rsi_attestation_token_init(desc->inblob, desc->inblob_len);
if (max_size <= 0) {
ret = -EINVAL;
goto exit_migrate_enable;
}
/* Allocate outblob */
token = kvzalloc(max_size, GFP_KERNEL);
if (!token)
return -ENOMEM;
if (!token) {
ret = -ENOMEM;
goto exit_migrate_enable;
}
/*
* Since the outblob may not be physically contiguous, use a page
* to bounce the buffer from RMM.
*/
buf = alloc_pages_exact(RSI_GRANULE_SIZE, GFP_KERNEL);
if (!buf)
return -ENOMEM;
if (!buf) {
ret = -ENOMEM;
goto exit_migrate_enable;
}
/* Get the PA of the memory page(s) that were allocated */
info.granule = (unsigned long)virt_to_phys(buf);
@@ -144,21 +123,15 @@ static int arm_cca_report_new(struct tsm_report *report, void *data)
info.offset = 0;
do {
/*
* Schedule a call to retrieve a sub-granule chunk
* of data per loop iteration.
* Retrieve a sub-granule chunk of data per loop
* iteration.
*/
ret = smp_call_function_single(cpu,
arm_cca_attestation_continue,
(void *)&info, true);
if (ret != 0) {
token_size = 0;
goto exit_free_granule_page;
}
} while (info.result == RSI_INCOMPLETE &&
rsi_result = arm_cca_attestation_continue(&info);
} while (rsi_result == RSI_INCOMPLETE &&
info.offset < RSI_GRANULE_SIZE);
/* Break out in case of failure */
if (info.result != RSI_SUCCESS && info.result != RSI_INCOMPLETE) {
if (rsi_result != RSI_SUCCESS && rsi_result != RSI_INCOMPLETE) {
ret = -ENXIO;
token_size = 0;
goto exit_free_granule_page;
@@ -173,12 +146,14 @@ static int arm_cca_report_new(struct tsm_report *report, void *data)
break;
memcpy(&token[token_size], buf, info.offset);
token_size += info.offset;
} while (info.result == RSI_INCOMPLETE);
} while (rsi_result == RSI_INCOMPLETE);
report->outblob = no_free_ptr(token);
exit_free_granule_page:
report->outblob_len = token_size;
free_pages_exact(buf, RSI_GRANULE_SIZE);
exit_migrate_enable:
migrate_enable();
return ret;
}