Re: [PATCH RFC V2 12/17] memremap: Add zone device access protection

On Fri, Jul 17, 2020 at 12:20:51AM -0700, ira.weiny@intel.com wrote:

+void dev_access_disable(void) +{

• unsigned long flags;
• if (!static_branch_unlikely(&dev_protection_static_key))

• return;
  

• local_irq_save(flags);
• current->dev_page_access_ref--;
• if (current->dev_page_access_ref == 0)

if (!--current->dev_page_access_ref)

• pks_update_protection(dev_page_pkey, PKEY_DISABLE_ACCESS);
  

• local_irq_restore(flags);

+} +EXPORT_SYMBOL_GPL(dev_access_disable);

+void dev_access_enable(void) +{

• unsigned long flags;
• if (!static_branch_unlikely(&dev_protection_static_key))

• return;
  

• local_irq_save(flags);
• /* 0 clears the PKEY_DISABLE_ACCESS bit, allowing access */
• if (current->dev_page_access_ref == 0)

• pks_update_protection(dev_page_pkey, 0);
  

• current->dev_page_access_ref++;

if (!current->dev_page_access_ref++)

• local_irq_restore(flags);

+} +EXPORT_SYMBOL_GPL(dev_access_enable);

Also, you probably want something like:

static __always_inline devm_access_disable(void) { if (static_branch_unlikely(&dev_protection_static_key)) __devm_access_disable(); }

static __always_inline devm_access_enable(void) { if (static_branch_unlikely(&dev_protection_static_key)) __devm_access_enable(); }