Messages in this thread |  | | From | Andy Lutomirski <> | Date | Mon, 8 Jun 2015 17:13:21 -0700 | Subject | Re: [PATCH 2/4] x86/asm/entry: Untangle 'ia32_sysenter_target' into two entry points: entry_SYSENTER_32 and entry_SYSENTER_compat |
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On Mon, Jun 8, 2015 at 1:34 AM, Ingo Molnar <mingo@kernel.org> wrote: > So the SYSENTER instruction is pretty quirky and it has different behavior > depending on bitness and CPU maker. > > Yet we create a false sense of coherency by naming it 'ia32_sysenter_target' > in both of the cases. > > Split the name into its two uses: > > ia32_sysenter_target (32) -> entry_SYSENTER_32 > ia32_sysenter_target (64) -> entry_SYSENTER_compat >
Now that I'm rebasing my pile on top of this, I have a minor gripe about this one. There are (in my mind, anyway), two SYSENTER instructions: the 32-bit one and the 64-bit one. (That is, there's SYSENTER32, which happens when you do SYSENTER in 32-bit or compat mode, and SYSENTER64, which happens when you do SYSENTER in long mode.) SYSENTER32, from user code's perspective, does the same thing in either case [1]. That means that it really does make sense that we'd have two implementations of the same entry point, one written in 32-bit asm and one written in 64-bit asm.
The patch I'm rebasing merges the two wrmsrs to MSR_IA32_SYSENTER, and this change makes it uglier.
[1] Sort of. We probably have differently nonsensical calling conventions, but that's our fault and has nothing to do with the hardware.
--Andy
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