diff options
author | Juergen Gross <jgross@suse.com> | 2021-03-11 15:23:13 +0100 |
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committer | Borislav Petkov <bp@suse.de> | 2021-03-11 19:51:49 +0100 |
commit | 4e6292114c741221479046515b1aa8145cf1e3f6 (patch) | |
tree | f3a8bb9b151d60b60c26f81872ebcc32cf55a94b /arch/x86/kernel/alternative.c | |
parent | 2fe2a2c7a97c9bc32acc79154b75e754280f7867 (diff) | |
download | linux-4e6292114c741221479046515b1aa8145cf1e3f6.tar.bz2 |
x86/paravirt: Add new features for paravirt patching
For being able to switch paravirt patching from special cased custom
code sequences to ALTERNATIVE handling some X86_FEATURE_* are needed
as new features. This enables to have the standard indirect pv call
as the default code and to patch that with the non-Xen custom code
sequence via ALTERNATIVE patching later.
Make sure paravirt patching is performed before alternatives patching.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210311142319.4723-9-jgross@suse.com
Diffstat (limited to 'arch/x86/kernel/alternative.c')
-rw-r--r-- | arch/x86/kernel/alternative.c | 30 |
1 files changed, 28 insertions, 2 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 133b549dc091..76ad4ce454c0 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -28,6 +28,7 @@ #include <asm/insn.h> #include <asm/io.h> #include <asm/fixmap.h> +#include <asm/paravirt.h> int __read_mostly alternatives_patched; @@ -733,6 +734,33 @@ void __init alternative_instructions(void) * patching. */ + /* + * Paravirt patching and alternative patching can be combined to + * replace a function call with a short direct code sequence (e.g. + * by setting a constant return value instead of doing that in an + * external function). + * In order to make this work the following sequence is required: + * 1. set (artificial) features depending on used paravirt + * functions which can later influence alternative patching + * 2. apply paravirt patching (generally replacing an indirect + * function call with a direct one) + * 3. apply alternative patching (e.g. replacing a direct function + * call with a custom code sequence) + * Doing paravirt patching after alternative patching would clobber + * the optimization of the custom code with a function call again. + */ + paravirt_set_cap(); + + /* + * First patch paravirt functions, such that we overwrite the indirect + * call with the direct call. + */ + apply_paravirt(__parainstructions, __parainstructions_end); + + /* + * Then patch alternatives, such that those paravirt calls that are in + * alternatives can be overwritten by their immediate fragments. + */ apply_alternatives(__alt_instructions, __alt_instructions_end); #ifdef CONFIG_SMP @@ -751,8 +779,6 @@ void __init alternative_instructions(void) } #endif - apply_paravirt(__parainstructions, __parainstructions_end); - restart_nmi(); alternatives_patched = 1; } |