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

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

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 46b26bfee27ba81267703a1ceac7c0e082f1e5ec..1e762c210f1b4afa6a4789f9b9842c30d58775fe 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2742,8 +2742,6 @@
        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 30571fdaaf6ff9d54efb5e3b3c07f41a7e473a55..a481763a37763ada0586d2486f3a062066a3712d 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -46,17 +46,6 @@ 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)                                          \
@@ -599,9 +588,6 @@ 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;