#include <linux/syscalls.h>
#include <asm/processor.h>
+#include <asm/pkru.h>
#include <asm/fpu/internal.h>
#include <asm/mmu_context.h>
#include <asm/prctl.h>
log_lvl, d3, d6, d7);
}
- if (boot_cpu_has(X86_FEATURE_OSPKE))
+ if (cpu_feature_enabled(X86_FEATURE_OSPKE))
printk("%sPKRU: %08x\n", log_lvl, read_pkru());
}
}
}
+/*
+ * Store prev's PKRU value and load next's PKRU value if they differ. PKRU
+ * is not XSTATE managed on context switch because that would require a
+ * lookup in the task's FPU xsave buffer and require to keep that updated
+ * in various places.
+ */
+static __always_inline void x86_pkru_load(struct thread_struct *prev,
+ struct thread_struct *next)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
+ return;
+
+ /* Stash the prev task's value: */
+ prev->pkru = rdpkru();
+
+ /*
+ * PKRU writes are slightly expensive. Avoid them when not
+ * strictly necessary:
+ */
+ if (prev->pkru != next->pkru)
+ wrpkru(next->pkru);
+}
+
static __always_inline void x86_fsgsbase_load(struct thread_struct *prev,
struct thread_struct *next)
{
x86_fsgsbase_load(prev, next);
+ x86_pkru_load(prev, next);
+
/*
* Switch the PDA and FPU contexts.
*/