linux-kernel - [PATCH 03/12] x86, pkey: pkru xsave fields and data structure

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Date:	Thu, 07 May 2015 10:41:34 -0700
From:	Dave Hansen <dave@...1.net>
To:	dave@...1.net
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [PATCH 03/12] x86, pkey: pkru xsave fields and data structure


The protection keys register (PKRU) is saved and restored using
xsave.  Define the data structure that we will use to access it
inside the xsave buffer, and also double-check that the new
structure matches the size that comes out of the CPU.

---

 b/arch/x86/include/asm/processor.h |    9 +++++++++
 b/arch/x86/include/asm/xsave.h     |    3 ++-
 b/arch/x86/kernel/xsave.c          |    7 +++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff -puN arch/x86/include/asm/processor.h~pkeys-2-xsave arch/x86/include/asm/processor.h
--- a/arch/x86/include/asm/processor.h~pkeys-2-xsave	2015-05-07 10:31:41.756204056 -0700
+++ b/arch/x86/include/asm/processor.h	2015-05-07 10:31:41.763204372 -0700
@@ -406,6 +406,15 @@ struct bndcsr {
 	u64 bndstatus;
 } __packed;
 
+/*
+ * "The size of XSAVE state component for PKRU is 8 bytes,
+ *  of which only the first four bytes are used...".
+ */
+struct pkru {
+	u32 pkru;
+	u32 pkru_unused;
+} __packed;
+
 struct xsave_hdr_struct {
 	u64 xstate_bv;
 	u64 xcomp_bv;
diff -puN arch/x86/include/asm/xsave.h~pkeys-2-xsave arch/x86/include/asm/xsave.h
--- a/arch/x86/include/asm/xsave.h~pkeys-2-xsave	2015-05-07 10:31:41.758204147 -0700
+++ b/arch/x86/include/asm/xsave.h	2015-05-07 10:31:41.764204417 -0700
@@ -14,6 +14,7 @@
 #define XSTATE_OPMASK		0x20
 #define XSTATE_ZMM_Hi256	0x40
 #define XSTATE_Hi16_ZMM		0x80
+#define XSTATE_PKRU		0x200
 
 #define XSTATE_FPSSE	(XSTATE_FP | XSTATE_SSE)
 #define XSTATE_AVX512	(XSTATE_OPMASK | XSTATE_ZMM_Hi256 | XSTATE_Hi16_ZMM)
@@ -33,7 +34,7 @@
 			| XSTATE_OPMASK | XSTATE_ZMM_Hi256 | XSTATE_Hi16_ZMM)
 
 /* Supported features which require eager state saving */
-#define XSTATE_EAGER	(XSTATE_BNDREGS | XSTATE_BNDCSR)
+#define XSTATE_EAGER	(XSTATE_BNDREGS | XSTATE_BNDCSR | XSTATE_PKRU)
 
 /* All currently supported features */
 #define XCNTXT_MASK	(XSTATE_LAZY | XSTATE_EAGER)
diff -puN arch/x86/kernel/xsave.c~pkeys-2-xsave arch/x86/kernel/xsave.c
--- a/arch/x86/kernel/xsave.c~pkeys-2-xsave	2015-05-07 10:31:41.760204237 -0700
+++ b/arch/x86/kernel/xsave.c	2015-05-07 10:31:41.764204417 -0700
@@ -528,6 +528,13 @@ void setup_xstate_comp(void)
 					+ xstate_comp_sizes[i-1];
 
 	}
+	/*
+	 * Check that the size of the "PKRU" xsave area
+	 * which the CPU knows about matches the kernel
+	 * data structure that we have defined.
+	 */
+	if ((xstate_features >= XSTATE_PKRU) && xstate_comp_sizes[XSTATE_PKRU])
+		WARN_ON(xstate_comp_sizes[XSTATE_PKRU] != sizeof(struct pkru));
 }
 
 /*
_
--
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