[pve-devel] [PATCH kernel] backport new FPU register copy helpers

[Fabian Grünbichler]

small nit inline, otherwise

Acked-by: Fabian Grünbichler <f.gruenbichler.proxmox.com>

On September 27, 2019 12:49 pm, Thomas Lamprecht wrote:
> This allows us to fix the ZFS SIMD patch for 5.0 kernel way easier,
> as we can use the same code path as used for 5.2 and newer kernels
> there.
> 
> The helper itself do not do anything, just exposes them for modules
> to use.
> 
> Signed-off-by: Thomas Lamprecht <t.lamprecht at proxmox.com>
> ---
>  ...kport-copy_kernel_to_XYZ_err-helpers.patch | 102 ++++++++++++++++++
>  1 file changed, 102 insertions(+)
>  create mode 100644 patches/kernel/0007-x86-fpu-backport-copy_kernel_to_XYZ_err-helpers.patch
> 
> diff --git a/patches/kernel/0007-x86-fpu-backport-copy_kernel_to_XYZ_err-helpers.patch b/patches/kernel/0007-x86-fpu-backport-copy_kernel_to_XYZ_err-helpers.patch
> new file mode 100644
> index 000000000000..94fc630a0ca9
> --- /dev/null
> +++ b/patches/kernel/0007-x86-fpu-backport-copy_kernel_to_XYZ_err-helpers.patch
> @@ -0,0 +1,102 @@
> +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
> +From: Sebastian Andrzej Siewior <bigeasy at linutronix.de>

I'd move this down below, and put your name here ;)

> +Date: Wed, 3 Apr 2019 18:41:50 +0200
> +Subject: [PATCH] x86/fpu: backport copy_kernel_to_XYZ_err helpers
> +MIME-Version: 1.0
> +Content-Type: text/plain; charset=UTF-8
> +Content-Transfer-Encoding: 8bit
> +
> +partial cherry-pick from upstream 5.2 "86/fpu: Restore from kernel
> +memory on the 64-bit path too"
> +commit 926b21f37b072ae4c117052de45a975c6d468fec
> +
> +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.

(as discussed offline, there is definitely still an issue with upstream 
ZFS code here, as there is no error handling there whatsoever? but that 
is something to continue on GH I guess.)

> +
> +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 at 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
> -- 
> 2.20.1
> 
> 
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