Messages in this thread | | | Subject | Re: [PATCH] x86, paravirt: BUG_ON on {rd,wr}msr exceptions | From | "H. Peter Anvin" <> | Date | Mon, 28 Jul 2014 13:43:36 -0700 |
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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@redhat.com> 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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