linux-kernel - [PATCH v3 11/21] x86/fpu/xstate: Update xstate buffer address finder to support dynamic xstate

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Message-Id: <20201223155717.19556-12-chang.seok.bae@intel.com>
Date:   Wed, 23 Dec 2020 07:57:07 -0800
From:   "Chang S. Bae" <chang.seok.bae@...el.com>
To:     bp@...e.de, luto@...nel.org, tglx@...utronix.de, mingo@...nel.org,
        x86@...nel.org
Cc:     len.brown@...el.com, dave.hansen@...el.com, jing2.liu@...el.com,
        ravi.v.shankar@...el.com, linux-kernel@...r.kernel.org,
        chang.seok.bae@...el.com
Subject: [PATCH v3 11/21] x86/fpu/xstate: Update xstate buffer address finder to support dynamic xstate

__raw_xsave_addr() returns the requested component's pointer in an xstate
buffer, by simply looking up the offset table. The offset used to be fixed,
but, with dynamic user states, it becomes variable.

get_xstate_size() has a routine to find an offset at runtime. Refactor to
use it for the address finder.

No functional change until the kernel enables dynamic user states.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Reviewed-by: Len Brown <len.brown@...el.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
 arch/x86/kernel/fpu/xstate.c | 82 +++++++++++++++++++++++-------------
 1 file changed, 52 insertions(+), 30 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 8dfbc7d1702a..6b863b2ca405 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -133,15 +133,50 @@ static bool xfeature_is_supervisor(int xfeature_nr)
 	return ecx & 1;
 }
 
+/*
+ * Available once those arrays for the offset, size, and alignment info are set up,
+ * by setup_xstate_features().
+ */
+static unsigned int __get_xstate_comp_offset(u64 mask, int feature_nr)
+{
+	u64 xmask = BIT_ULL(feature_nr + 1) - 1;
+	unsigned int next_offset, offset = 0;
+	int i;
+
+	if ((mask & xmask) == (xfeatures_mask_all & xmask))
+		return xstate_comp_offsets[feature_nr];
+
+	/*
+	 * Calculate the size by summing up each state together, since no known
+	 * offset found with the xstate buffer format out of the given mask.
+	 */
+
+	next_offset = FXSAVE_SIZE + XSAVE_HDR_SIZE;
+
+	for (i = FIRST_EXTENDED_XFEATURE; i <= feature_nr; i++) {
+		if (!(mask & BIT_ULL(i)))
+			continue;
+
+		offset = xstate_aligns[i] ? ALIGN(next_offset, 64) : next_offset;
+		next_offset += xstate_sizes[i];
+	}
+
+	return offset;
+}
+
+static unsigned int get_xstate_comp_offset(struct fpu *fpu, int feature_nr)
+{
+	return __get_xstate_comp_offset(fpu->state_mask, feature_nr);
+}
+
 /*
  * Available once those arrays for the offset, size, and alignment info are set up,
  * by setup_xstate_features().
  */
 unsigned int get_xstate_size(u64 mask)
 {
-	unsigned int size;
-	u64 xmask;
-	int i, nr;
+	unsigned int offset;
+	int nr;
 
 	if (!mask)
 		return 0;
@@ -155,24 +190,8 @@ unsigned int get_xstate_size(u64 mask)
 	if (!using_compacted_format())
 		return xstate_offsets[nr] + xstate_sizes[nr];
 
-	xmask = BIT_ULL(nr + 1) - 1;
-
-	if (mask == (xmask & xfeatures_mask_all))
-		return xstate_comp_offsets[nr] + xstate_sizes[nr];
-
-	/*
-	 * Calculate the size by summing up each state together, since no known
-	 * size found with the xstate buffer format out of the given mask.
-	 */
-	for (size = FXSAVE_SIZE + XSAVE_HDR_SIZE, i = FIRST_EXTENDED_XFEATURE; i <= nr; i++) {
-		if (!(mask & BIT_ULL(i)))
-			continue;
-
-		if (xstate_aligns[i])
-			size = ALIGN(size, 64);
-		size += xstate_sizes[i];
-	}
-	return size;
+	offset = __get_xstate_comp_offset(mask, nr);
+	return offset + xstate_sizes[nr];
 }
 
 /*
@@ -988,17 +1007,20 @@ static void *__raw_xsave_addr(struct fpu *fpu, int xfeature_nr)
 {
 	void *xsave;
 
-	if (!xfeature_enabled(xfeature_nr)) {
-		WARN_ON_FPU(1);
-		return NULL;
-	}
-
-	if (fpu)
-		xsave = __xsave(fpu);
-	else
+	if (!xfeature_enabled(xfeature_nr))
+		goto not_found;
+	else if (!fpu)
 		xsave = &init_fpstate.xsave;
+	else if (!(fpu->state_mask & BIT_ULL(xfeature_nr)))
+		goto not_found;
+	else
+		xsave = __xsave(fpu);
+
+	return xsave + get_xstate_comp_offset(fpu, xfeature_nr);
 
-	return xsave + xstate_comp_offsets[xfeature_nr];
+not_found:
+	WARN_ON_FPU(1);
+	return NULL;
 }
 /*
  * Given the xsave area and a state inside, this function returns the
-- 
2.17.1