Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | Is GET_CR0_INTO_EAX macro unused? | Date | Mon, 2 Oct 2017 14:36:38 +0200 |
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Hi Andy,
From by git archaeology, looks like last use of GET_CR0_INTO_EAX was removed long ago, in 2008 (see commit below).
Right now, I only grep it here in a comment in entry_32.S: /* * We use macros for low-level operations which need to be overridden * for paravirtualization. The following will never clobber any registers: * INTERRUPT_RETURN (aka. "iret") * GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")
To support GET_CR0_INTO_EAX, paravirt has PV_CPU_read_cr0 a.k.a. struct pv_cpu_ops::read_cr0 and a bunch of code to support it for each hypervisor.
Can we delete it? Or am I missing a non-obvious place where this macro is still in use?
commit 7643e9b936b4af31ba4851eb7d5b3a3bfad52502 Author: Alexander van Heukelum <heukelum@fastmail.fm> Date: Tue Sep 9 21:56:02 2008 +0200
i386: convert hardware exception 7 to an interrupt gate
Handle no coprocessor exception with interrupt initially off.
device_not_available in entry_32.S calls either math_state_restore or math_emulate. This patch adds an extra indirection to be able to re-enable interrupts explicitly in traps_32.c
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm> Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index 109792b..5a88585 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -760,20 +760,9 @@ ENTRY(device_not_available) RING0_INT_FRAME pushl $-1 # mark this as an int CFI_ADJUST_CFA_OFFSET 4 - SAVE_ALL - GET_CR0_INTO_EAX - testl $0x4, %eax # EM (math emulation bit) - jne device_not_available_emulate - preempt_stop(CLBR_ANY) - call math_state_restore - jmp ret_from_exception -device_not_available_emulate: - pushl $0 # temporary storage for ORIG_EIP + pushl $do_device_not_available CFI_ADJUST_CFA_OFFSET 4 - call math_emulate - addl $4, %esp - CFI_ADJUST_CFA_OFFSET -4 - jmp ret_from_exception + jmp error_code CFI_ENDPROC END(device_not_available)
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