Messages in this thread Patch in this message | | | Date | Tue, 17 Mar 2015 12:20:15 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH RFC 0/2] x86/fpu: avoid "xstate_fault" in xsave_user/xrestore_user |
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On Tue, Mar 17, 2015 at 11:00:46AM +0100, Quentin Casasnovas wrote: > Fair point, but AFAIUI we can't do check_insn(XSAVES) alone as of today, > and the "..." in your "check_isns(XSAVEOPT, ...)" code above would still > need to contain the outputs operands.
I think we can do this (see diff the end of this mail).
It still explodes my guest with:
[ 2.940379] Freeing unused kernel memory: 2860K (ffffffff81a39000 - ffffffff81d04000) [ 2.980722] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b [ 2.980722] [ 2.984096] CPU: 1 PID: 1 Comm: init Not tainted 4.0.0-rc3+ #22 [ 2.984096] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014 [ 2.984096] ffff88007bcf0000 ffff88007bcfbc58 ffffffff81675eb9 0000000000000001 [ 2.984096] ffffffff818a9ae8 ffff88007bcfbcd8 ffffffff816745be ffff88007bcf0000 [ 2.984096] 0000000000000010 ffff88007bcfbce8 ffff88007bcfbc88 ffff88007bfcc0b0 [ 2.984096] Call Trace: [ 2.984096] [<ffffffff81675eb9>] dump_stack+0x4f/0x7b [ 2.984096] [<ffffffff816745be>] panic+0xc0/0x1dc [ 2.984096] [<ffffffff81056143>] do_exit+0xc13/0xc50 [ 2.984096] [<ffffffff810574a4>] do_group_exit+0x54/0xe0 [ 2.984096] [<ffffffff81065526>] get_signal+0x266/0xab0 [ 2.984096] [<ffffffff81002523>] do_signal+0x33/0xba0 [ 2.984096] [<ffffffff8109c88e>] ? put_lock_stats.isra.19+0xe/0x30 [ 2.984096] [<ffffffff8167dd81>] ? _raw_spin_unlock_irqrestore+0x41/0x80 [ 2.984096] [<ffffffff8167dd8b>] ? _raw_spin_unlock_irqrestore+0x4b/0x80 [ 2.984096] [<ffffffff8167f9f1>] ? retint_signal+0x11/0x90 [ 2.984096] [<ffffffff810030f5>] do_notify_resume+0x65/0x80 [ 2.984096] [<ffffffff8167fa26>] retint_signal+0x46/0x90 [ 2.984096] Kernel Offset: disabled [ 2.984096] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
because, AFAICT and from debugging so far, we call xrstor_state() without a previous xsave_state() in that path:
[ 3.304551] Freeing unused kernel memory: 2860K (ffffffff81a39000 - ffffffff81d04000) [ 3.346556] traps: xrstor_state [ 3.350418] CPU: 1 PID: 1 Comm: init Not tainted 4.0.0-rc3+ #21 [ 3.350418] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014 [ 3.350418] ffff88007b454000 ffff88007bcfbf18 ffffffff81676079 0000000000000000 [ 3.350418] ffff88007bcf0000 ffff88007bcfbf38 ffffffff810038b6 0000000000000000 [ 3.350418] 00007f6b95ba91c8 ffff88007bcfbf48 ffffffff81004433 00007ffeecd31bb0 [ 3.350418] Call Trace: [ 3.350418] [<ffffffff81676079>] dump_stack+0x4f/0x7b [ 3.350418] [<ffffffff810038b6>] math_state_restore+0xa6/0x220 [ 3.350418] [<ffffffff81004433>] do_device_not_available+0x23/0x30 [ 3.350418] [<ffffffff81680865>] device_not_available+0x15/0x20
so I need to sort that one out first.
But including the fault exception table in the macro is already an improvement IMO.
Thanks.
--- diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h index c9a6d68b8d62..0d0cc053c7cc 100644 --- a/arch/x86/include/asm/xsave.h +++ b/arch/x86/include/asm/xsave.h @@ -67,6 +67,51 @@ extern int init_fpu(struct task_struct *child); _ASM_EXTABLE(1b, 3b) \ : [err] "=r" (err) +#define XSTATE_OP(op, st, lmask, hmask, err) \ + asm volatile("1:" op "\n\t" \ + "2:\n\t" \ + ".pushsection .fixup,\"ax\"\n\t" \ + "3: movl $-1,%[err]\n\t" \ + "jmp 2b\n\t" \ + ".popsection\n\t" \ + _ASM_EXTABLE(1b, 3b) \ + : [err] "=r" (err) \ + : "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \ + : "memory") + +/* + * 661 and alt_end_marker labels below are defined in ALTERNATIVE* + * and we're reusing them here so as not to clutter this macro + * unnecessarily. + */ +#define XSTATE_XSAVE(st, lmask, hmask, err) \ + asm volatile(ALTERNATIVE_2(XSAVE, \ + XSAVEOPT, X86_FEATURE_XSAVEOPT, \ + XSAVES, X86_FEATURE_XSAVES) \ + "\n" \ + ".pushsection .fixup,\"ax\"\n" \ + "3: movl $-1, %[err]\n" \ + "jmp " alt_end_marker "b\n" \ + ".popsection\n" \ + _ASM_EXTABLE(661b, 3b) \ + : [err] "=r" (err) \ + : "D" (st), "a" (lmask), "d" (hmask) \ + : "memory") + +#define XSTATE_XRESTORE(st, lmask, hmask, err) \ + asm volatile(ALTERNATIVE(XRSTOR, \ + XRSTORS, X86_FEATURE_XSAVES) \ + "\n" \ + ".pushsection .fixup,\"ax\"\n" \ + "3: movl $-1, %[err]\n" \ + "jmp 663b\n" \ + ".popsection\n" \ + _ASM_EXTABLE(661b, 3b) \ + : [err] "=r" (err) \ + : "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \ + : "memory") + + /* * This function is called only during boot time when x86 caps are not set * up and alternative can not be used yet. @@ -77,20 +122,11 @@ static inline int xsave_state_booting(struct xsave_struct *fx, u64 mask) u32 hmask = mask >> 32; int err = 0; - WARN_ON(system_state != SYSTEM_BOOTING); - - if (boot_cpu_has(X86_FEATURE_XSAVES)) - asm volatile("1:"XSAVES"\n\t" - "2:\n\t" - xstate_fault - : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask) - : "memory"); + if (static_cpu_has_safe(X86_FEATURE_XSAVES)) + XSTATE_OP(XSAVES, fx, lmask, hmask, err); else - asm volatile("1:"XSAVE"\n\t" - "2:\n\t" - xstate_fault - : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask) - : "memory"); + XSTATE_OP(XSAVE, fx, lmask, hmask, err); + return err; } @@ -104,20 +140,12 @@ static inline int xrstor_state_booting(struct xsave_struct *fx, u64 mask) u32 hmask = mask >> 32; int err = 0; - WARN_ON(system_state != SYSTEM_BOOTING); + WARN_ON(system_state != SYSTEM_BOOTING); - if (boot_cpu_has(X86_FEATURE_XSAVES)) - asm volatile("1:"XRSTORS"\n\t" - "2:\n\t" - xstate_fault - : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask) - : "memory"); + if (static_cpu_has_safe(X86_FEATURE_XSAVES)) + XSTATE_OP(XRSTORS, fx, lmask, hmask, err); else - asm volatile("1:"XRSTOR"\n\t" - "2:\n\t" - xstate_fault - : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask) - : "memory"); + XSTATE_OP(XRSTOR, fx, lmask, hmask, err); return err; } @@ -141,18 +169,7 @@ static inline int xsave_state(struct xsave_struct *fx, u64 mask) * * If none of xsaves and xsaveopt is enabled, use xsave. */ - alternative_input_2( - "1:"XSAVE, - XSAVEOPT, - X86_FEATURE_XSAVEOPT, - XSAVES, - X86_FEATURE_XSAVES, - [fx] "D" (fx), "a" (lmask), "d" (hmask) : - "memory"); - asm volatile("2:\n\t" - xstate_fault - : "0" (0) - : "memory"); + XSTATE_XSAVE(fx, lmask, hmask, err); return err; } @@ -170,17 +187,7 @@ static inline int xrstor_state(struct xsave_struct *fx, u64 mask) * Use xrstors to restore context if it is enabled. xrstors supports * compacted format of xsave area which is not supported by xrstor. */ - alternative_input( - "1: " XRSTOR, - XRSTORS, - X86_FEATURE_XSAVES, - "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask) - : "memory"); - - asm volatile("2:\n" - xstate_fault - : "0" (0) - : "memory"); + XSTATE_XRESTORE(fx, lmask, hmask, err); return err; } -- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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