pve-kernel-lowlatency-qoup/patches/kernel/0007-x86-fpu-backport-copy_kernel_to_XYZ_err-helpers.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Thomas Lamprecht <t.lamprecht@proxmox.com>
Date: Wed, 3 Apr 2019 18:41:50 +0200
Subject: [PATCH] x86/fpu: backport copy_kernel_to_XYZ_err helpers
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partial cherry-pick from upstream 5.2 "86/fpu: Restore from kernel
memory on the 64-bit path too"
commit 926b21f37b072ae4c117052de45a975c6d468fec
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Namely, only backport the added helpers, none of the semantic changes.

relevant parts of the original commit message:
> In order to avoid that mess, copy the FPU state from userland, validate
> it and then load it. The copy_kernel_…() helpers are basically just
> like the old helpers except that they operate on kernel memory and the
> fault handler just sets the error value and the caller handles it.

Link: https://lkml.kernel.org/r/20190403164156.19645-22-bigeasy@linutronix.de
(partial cherry picked from commit 926b21f37b072ae4c117052de45a975c6d468fec)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 arch/x86/include/asm/fpu/internal.h | 43 +++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index fa2c93cb42a2..f3193ab0a2fb 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -122,6 +122,21 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
 	err;								\
 })
 
+#define kernel_insn_err(insn, output, input...)				\
+({									\
+	int err;							\
+	asm volatile("1:" #insn "\n\t"					\
+		     "2:\n"						\
+		     ".section .fixup,\"ax\"\n"				\
+		     "3:  movl $-1,%[err]\n"				\
+		     "    jmp  2b\n"					\
+		     ".previous\n"					\
+		     _ASM_EXTABLE(1b, 3b)				\
+		     : [err] "=r" (err), output				\
+		     : "0"(0), input);					\
+	err;								\
+})
+
 #define kernel_insn(insn, output, input...)				\
 	asm volatile("1:" #insn "\n\t"					\
 		     "2:\n"						\
@@ -158,6 +173,14 @@ static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
 	}
 }
 
+static inline int copy_kernel_to_fxregs_err(struct fxregs_state *fx)
+{
+	if (IS_ENABLED(CONFIG_X86_32))
+		return kernel_insn_err(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
+	else
+		return kernel_insn_err(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
+}
+
 static inline int copy_user_to_fxregs(struct fxregs_state __user *fx)
 {
 	if (IS_ENABLED(CONFIG_X86_32))
@@ -175,6 +198,11 @@ static inline void copy_kernel_to_fregs(struct fregs_state *fx)
 	kernel_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
 }
 
+static inline int copy_kernel_to_fregs_err(struct fregs_state *fx)
+{
+	return kernel_insn_err(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
+}
+
 static inline int copy_user_to_fregs(struct fregs_state __user *fx)
 {
 	return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
@@ -400,6 +428,21 @@ static inline int copy_user_to_xregs(struct xregs_state __user *buf, u64 mask)
 	return err;
 }
 
+/*
+ * Restore xstate from kernel space xsave area, return an error code instead of
+ * an exception.
+ */
+static inline int copy_kernel_to_xregs_err(struct xregs_state *xstate, u64 mask)
+{
+	u32 lmask = mask;
+	u32 hmask = mask >> 32;
+	int err;
+
+	XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
+
+	return err;
+}
+
 /*
  * These must be called with preempt disabled. Returns
  * 'true' if the FPU state is still intact and we can