On Mon, Nov 06, 2017 at 12:57:15AM -0800, Ram Pai wrote:

PAPR defines 'ibm,processor-storage-keys' property. It exports two values. The first value holds the number of data-access keys and the second holds the number of instruction-access keys. Due to a bug in the firmware, instruction-access keys is always reported as zero. However any key can be configured to disable data-access and/or disable execution-access. The inavailablity of the second value is not a big handicap, though it could have been used to determine if the platform supported disable-execution-access.

Non PAPR platforms do not define this property in the device tree yet. Here, we hardcode CPUs that support pkey by consulting PowerISA3.0

This patch calculates the number of keys supported by the platform. Alsi it determines the platform support for read/write/execution access support for pkeys.

Signed-off-by: Ram Pai linuxram@us.ibm.com

....snip...

+static inline bool pkey_mmu_enabled(void) +{

• if (firmware_has_feature(FW_FEATURE_LPAR))

• return pkeys_total;
  

• else

• return cpu_has_feature(CPU_FTR_PKEY);
  

+}

void __init pkey_initialize(void) { int os_reserved, i; @@ -46,14 +54,9 @@ void __init pkey_initialize(void) __builtin_popcountl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) != (sizeof(u64) * BITS_PER_BYTE));

• /*

• * Disable the pkey system till everything is in place. A subsequent
  

• * patch will enable it.
  

• */
  

• static_branch_enable(&pkey_disabled);
• /* Lets assume 32 keys */
• pkeys_total = 32;

vvvvvvvvvvvvvvvvvvvv

• /* Let's assume 32 keys if we are not told the number of pkeys. */
• if (!pkeys_total)

• pkeys_total = 32;
  

^^^^^^^^^^^^^^^^^^^^

There is a small bug here.

On a KVM guest or a LPAR, if the device tree does not expose pkeys, the pkey-subsystem must be disabled.

Unfortunately, the code above blindly sets the pkeys_total to 32. This confuses pkey_mmu_enabled() into returning true. Because of this bug the guest errorneously enables pkey-subsystem.

The fix is to delete the code marked above.

/* * Adjust the upper limit, based on the number of bits supported by @@ -62,11 +65,19 @@ void __init pkey_initialize(void) pkeys_total = min_t(int, pkeys_total, (ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT));

• if (!pkey_mmu_enabled() || radix_enabled() || !pkeys_total)

• static_branch_enable(&pkey_disabled);
  

• else

• static_branch_disable(&pkey_disabled);
  

RP

-- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html