As much as I hate adding new pvops, it might be the better answer, especially since those are the real native ops.
On July 28, 2014 1:39:55 PM PDT, Eduardo Habkost <ehabkost@xxxxxxxxxx> wrote:
>On Mon, Jul 28, 2014 at 12:18:10PM -0700, H. Peter Anvin wrote:
>> On 07/28/2014 12:04 PM, Eduardo Habkost wrote:
>> > When CONFIG_PARAVIRT is enabled, the kernel is ignoring exceptions
>on
>> > the {rd,wr}msr instructions. This makes serious issues (either on
>the
>> > guest kernel, or on the host) be silently ignored, and is different
>from
>> > the native MSR code (which does not ignore the exceptions).
>> >
>> > As paravirt.h already includes linux/bug.h, I don't see what was
>the
>> > original issue preventing BUG_ON from being used.
>> >
>> > Change rdmsr(), wrmsr(), and rdmsrl() to BUG_ON() on errors.
>>
>> How much does this bloat the kernel?
>
>It seems to add 8 bytes to each {wr,rd}msr() call (4 extra
>instructions:
>test, jmp, ud2, jmp).
>
>allyesconfig, paravirt enabled, before:
>
> text data bss dec hex filename
>108368312 23500872 55705600 187574784 b2e2a00
>vmlinux
>
>allyesconfig, paravirt enabled, after:
>
> text data bss dec hex filename
>108384438 23500904 55717888 187603230 b2e991e
>vmlinux
>
>allyesconfig vmlinux is 28446 bytes larger.
>
>An alternative is to add read_msr_unsafe() & write_msr_unsafe() fields
>to pv_cpu_ops, pointing to native_read_msr() & native_write_msr().
--
Sent from my mobile phone. Please pardon brevity and lack of formatting.
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