x86/paravirt: Remove 'noreplace-paravirt' cmdline option

commit 12c69f1e94c89d40696e83804dd2f0965b5250cd upstream.

The 'noreplace-paravirt' option disables paravirt patching, leaving the
original pv indirect calls in place.

That's highly incompatible with retpolines, unless we want to uglify
paravirt even further and convert the paravirt calls to retpolines.

As far as I can tell, the option doesn't seem to be useful for much
other than introducing surprising corner cases and making the kernel
vulnerable to Spectre v2.  It was probably a debug option from the early
paravirt days.  So just remove it.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Link: https://lkml.kernel.org/r/20180131041333.2x6blhxirc2kclrq@treble
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7b9b238c22fc7263bec8a7746bb0a3340f583dd3..9d10847d19988498bed8f35ee9b7a90bde90a7b8 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2271,8 +2271,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
        norandmaps      Don't use address space randomization.  Equivalent to
                        echo 0 > /proc/sys/kernel/randomize_va_space
 
-       noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops
-
        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
                        with UP alternatives
 

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 576cc6d0669e72218957b8159251e2f452b70098..b44d458e51188f60cea0b5e6e04c2b2f2b820f22 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -41,17 +41,6 @@ static int __init setup_noreplace_smp(char *str)
 }
 __setup("noreplace-smp", setup_noreplace_smp);
 
-#ifdef CONFIG_PARAVIRT
-static int __initdata_or_module noreplace_paravirt = 0;
-
-static int __init setup_noreplace_paravirt(char *str)
-{
-       noreplace_paravirt = 1;
-       return 1;
-}
-__setup("noreplace-paravirt", setup_noreplace_paravirt);
-#endif
-
 #define DPRINTK(fmt, args...)                                          \
 do {                                                                   \
        if (debug_alternative)                                          \
@@ -574,9 +563,6 @@ void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
        struct paravirt_patch_site *p;
        char insnbuf[MAX_PATCH_LEN];
 
-       if (noreplace_paravirt)
-               return;
-
        for (p = start; p < end; p++) {
                unsigned int used;