[PATCH v5 00/12] x86: major paravirt cleanup

[PATCH v5 00/12] x86: major paravirt cleanup

[Juergen Gross]

This is a major cleanup of the paravirt infrastructure aiming at
eliminating all custom code patching via paravirt patching.

This is achieved by using ALTERNATIVE instead, leading to the ability
to give objtool access to the patched in instructions.

In order to remove most of the 32-bit special handling from pvops the
time related operations are switched to use static_call() instead.

At the end of this series all paravirt patching has to do is to
replace indirect calls with direct ones. In a further step this could
be switched to static_call(), too.

Changes in V5:
- patches 1-5 of V4 dropped, as already applied
- new patches 1+3
- fixed patch 2
- split V4 patch 8 into patches 4+5
- use flag byte instead of negative feature bit for "not feature"

Changes in V4:
- fixed several build failures
- removed objtool patch, as objtool patches are in tip now
- added patch 1 for making usage of static_call easier
- even more cleanup

Changes in V3:
- added patches 7 and 12
- addressed all comments

Changes in V2:
- added patches 5-12

Juergen Gross (12):
  staticcall: move struct static_call_key definition to
    static_call_types.h
  x86/paravirt: switch time pvops functions to use static_call()
  x86/alternative: drop feature parameter from ALTINSTR_REPLACEMENT()
  x86/alternative: support not-feature
  x86/alternative: support ALTERNATIVE_TERNARY
  x86: add new features for paravirt patching
  x86/paravirt: remove no longer needed 32-bit pvops cruft
  x86/paravirt: simplify paravirt macros
  x86/paravirt: switch iret pvops to ALTERNATIVE
  x86/paravirt: add new macros PVOP_ALT* supporting pvops in
    ALTERNATIVEs
  x86/paravirt: switch functions with custom code to ALTERNATIVE
  x86/paravirt: have only one paravirt patch function

 arch/arm/include/asm/paravirt.h               |  14 +-
 arch/arm/kernel/paravirt.c                    |   9 +-
 arch/arm64/include/asm/paravirt.h             |  14 +-
 arch/arm64/kernel/paravirt.c                  |  13 +-
 arch/x86/Kconfig                              |   1 +
 arch/x86/entry/entry_32.S                     |   4 +-
 arch/x86/entry/entry_64.S                     |   2 +-
 arch/x86/include/asm/alternative-asm.h        |  10 +
 arch/x86/include/asm/alternative.h            |  28 ++-
 arch/x86/include/asm/cpufeature.h             |   2 +
 arch/x86/include/asm/cpufeatures.h            |   2 +
 arch/x86/include/asm/irqflags.h               |   7 +-
 arch/x86/include/asm/mshyperv.h               |   2 +-
 arch/x86/include/asm/paravirt.h               | 167 +++++++-------
 arch/x86/include/asm/paravirt_types.h         | 210 +++++++-----------
 arch/x86/kernel/Makefile                      |   3 +-
 arch/x86/kernel/alternative.c                 |  37 ++-
 arch/x86/kernel/asm-offsets.c                 |   7 -
 arch/x86/kernel/cpu/vmware.c                  |   5 +-
 arch/x86/kernel/kvm.c                         |   2 +-
 arch/x86/kernel/kvmclock.c                    |   2 +-
 arch/x86/kernel/paravirt-spinlocks.c          |   9 +
 arch/x86/kernel/paravirt.c                    |  78 ++-----
 arch/x86/kernel/paravirt_patch.c              |  99 ---------
 arch/x86/kernel/tsc.c                         |   2 +-
 arch/x86/xen/enlighten_pv.c                   |   4 +-
 arch/x86/xen/time.c                           |  11 +-
 drivers/xen/time.c                            |   3 +-
 include/linux/static_call.h                   |  18 --
 include/linux/static_call_types.h             |  18 ++
 tools/include/linux/static_call_types.h       |  18 ++
 tools/objtool/arch/x86/include/arch/special.h |   6 +-
 32 files changed, 339 insertions(+), 468 deletions(-)
 delete mode 100644 arch/x86/kernel/paravirt_patch.c

-- 
2.26.2

[PATCH v5 01/12] staticcall: move struct static_call_key definition to static_call_types.h

[Juergen Gross]

Having the definition of static_call() in static_call_types.h makes
no sense as long struct static_call_key isn't defined there, as the
generic implementation of static_call() is referencing this structure.

So move the definition of struct static_call_key to static_call_types.h.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V5:
- new patch
---
 include/linux/static_call.h             | 18 ------------------
 include/linux/static_call_types.h       | 18 ++++++++++++++++++
 tools/include/linux/static_call_types.h | 18 ++++++++++++++++++
 3 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/include/linux/static_call.h b/include/linux/static_call.h
index 85ecc789f4ff..76b881259144 100644
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h
@@ -128,16 +128,6 @@ struct static_call_mod {
 	struct static_call_site *sites;
 };
 
-struct static_call_key {
-	void *func;
-	union {
-		/* bit 0: 0 = mods, 1 = sites */
-		unsigned long type;
-		struct static_call_mod *mods;
-		struct static_call_site *sites;
-	};
-};
-
 /* For finding the key associated with a trampoline */
 struct static_call_tramp_key {
 	s32 tramp;
@@ -187,10 +177,6 @@ extern long __static_call_return0(void);
 
 static inline int static_call_init(void) { return 0; }
 
-struct static_call_key {
-	void *func;
-};
-
 #define __DEFINE_STATIC_CALL(name, _func, _func_init)			\
 	DECLARE_STATIC_CALL(name, _func);				\
 	struct static_call_key STATIC_CALL_KEY(name) = {		\
@@ -243,10 +229,6 @@ static inline long __static_call_return0(void)
 
 static inline int static_call_init(void) { return 0; }
 
-struct static_call_key {
-	void *func;
-};
-
 static inline long __static_call_return0(void)
 {
 	return 0;
diff --git a/include/linux/static_call_types.h b/include/linux/static_call_types.h
index ae5662d368b9..5a00b8b2cf9f 100644
--- a/include/linux/static_call_types.h
+++ b/include/linux/static_call_types.h
@@ -58,11 +58,25 @@ struct static_call_site {
 	__raw_static_call(name);					\
 })
 
+struct static_call_key {
+	void *func;
+	union {
+		/* bit 0: 0 = mods, 1 = sites */
+		unsigned long type;
+		struct static_call_mod *mods;
+		struct static_call_site *sites;
+	};
+};
+
 #else /* !CONFIG_HAVE_STATIC_CALL_INLINE */
 
 #define __STATIC_CALL_ADDRESSABLE(name)
 #define __static_call(name)	__raw_static_call(name)
 
+struct static_call_key {
+	void *func;
+};
+
 #endif /* CONFIG_HAVE_STATIC_CALL_INLINE */
 
 #ifdef MODULE
@@ -77,6 +91,10 @@ struct static_call_site {
 
 #else
 
+struct static_call_key {
+	void *func;
+};
+
 #define static_call(name)						\
 	((typeof(STATIC_CALL_TRAMP(name))*)(STATIC_CALL_KEY(name).func))
 
diff --git a/tools/include/linux/static_call_types.h b/tools/include/linux/static_call_types.h
index ae5662d368b9..5a00b8b2cf9f 100644
--- a/tools/include/linux/static_call_types.h
+++ b/tools/include/linux/static_call_types.h
@@ -58,11 +58,25 @@ struct static_call_site {
 	__raw_static_call(name);					\
 })
 
+struct static_call_key {
+	void *func;
+	union {
+		/* bit 0: 0 = mods, 1 = sites */
+		unsigned long type;
+		struct static_call_mod *mods;
+		struct static_call_site *sites;
+	};
+};
+
 #else /* !CONFIG_HAVE_STATIC_CALL_INLINE */
 
 #define __STATIC_CALL_ADDRESSABLE(name)
 #define __static_call(name)	__raw_static_call(name)
 
+struct static_call_key {
+	void *func;
+};
+
 #endif /* CONFIG_HAVE_STATIC_CALL_INLINE */
 
 #ifdef MODULE
@@ -77,6 +91,10 @@ struct static_call_site {
 
 #else
 
+struct static_call_key {
+	void *func;
+};
+
 #define static_call(name)						\
 	((typeof(STATIC_CALL_TRAMP(name))*)(STATIC_CALL_KEY(name).func))
 
-- 
2.26.2

Re: [PATCH v5 01/12] staticcall: move struct static_call_key definition to static_call_types.h

[Peter Zijlstra]

On Mon, Mar 08, 2021 at 01:28:33PM +0100, Juergen Gross wrote:
> Having the definition of static_call() in static_call_types.h makes
> no sense as long struct static_call_key isn't defined there, as the
> generic implementation of static_call() is referencing this structure.
> 
> So move the definition of struct static_call_key to static_call_types.h.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>

s/staticcall/static_call/ on $Subject

[PATCH v5 02/12] x86/paravirt: switch time pvops functions to use static_call()

[Juergen Gross]

The time pvops functions are the only ones left which might be
used in 32-bit mode and which return a 64-bit value.

Switch them to use the static_call() mechanism instead of pvops, as
this allows quite some simplification of the pvops implementation.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V4:
- drop paravirt_time.h again
- don't move Hyper-V code (Michael Kelley)
V5:
- drop no longer needed Hyper-V modification (Michael Kelley)
- switch Arm and Arm64 to static_call(), too (kernel test robot)
---
 arch/arm/include/asm/paravirt.h       | 14 +++++---------
 arch/arm/kernel/paravirt.c            |  9 +++++++--
 arch/arm64/include/asm/paravirt.h     | 14 +++++---------
 arch/arm64/kernel/paravirt.c          | 13 +++++++++----
 arch/x86/Kconfig                      |  1 +
 arch/x86/include/asm/mshyperv.h       |  2 +-
 arch/x86/include/asm/paravirt.h       | 17 ++++++++++++++---
 arch/x86/include/asm/paravirt_types.h |  6 ------
 arch/x86/kernel/cpu/vmware.c          |  5 +++--
 arch/x86/kernel/kvm.c                 |  2 +-
 arch/x86/kernel/kvmclock.c            |  2 +-
 arch/x86/kernel/paravirt.c            | 16 ++++++++++++----
 arch/x86/kernel/tsc.c                 |  2 +-
 arch/x86/xen/time.c                   | 11 ++++-------
 drivers/xen/time.c                    |  3 ++-
 15 files changed, 66 insertions(+), 51 deletions(-)

diff --git a/arch/arm/include/asm/paravirt.h b/arch/arm/include/asm/paravirt.h
index cdbf02d9c1d4..95d5b0d625cd 100644
--- a/arch/arm/include/asm/paravirt.h
+++ b/arch/arm/include/asm/paravirt.h
@@ -3,23 +3,19 @@
 #define _ASM_ARM_PARAVIRT_H
 
 #ifdef CONFIG_PARAVIRT
+#include <linux/static_call_types.h>
+
 struct static_key;
 extern struct static_key paravirt_steal_enabled;
 extern struct static_key paravirt_steal_rq_enabled;
 
-struct pv_time_ops {
-	unsigned long long (*steal_clock)(int cpu);
-};
-
-struct paravirt_patch_template {
-	struct pv_time_ops time;
-};
+u64 dummy_steal_clock(int cpu);
 
-extern struct paravirt_patch_template pv_ops;
+DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
 
 static inline u64 paravirt_steal_clock(int cpu)
 {
-	return pv_ops.time.steal_clock(cpu);
+	return static_call(pv_steal_clock)(cpu);
 }
 #endif
 
diff --git a/arch/arm/kernel/paravirt.c b/arch/arm/kernel/paravirt.c
index 4cfed91fe256..7dd9806369fb 100644
--- a/arch/arm/kernel/paravirt.c
+++ b/arch/arm/kernel/paravirt.c
@@ -9,10 +9,15 @@
 #include <linux/export.h>
 #include <linux/jump_label.h>
 #include <linux/types.h>
+#include <linux/static_call.h>
 #include <asm/paravirt.h>
 
 struct static_key paravirt_steal_enabled;
 struct static_key paravirt_steal_rq_enabled;
 
-struct paravirt_patch_template pv_ops;
-EXPORT_SYMBOL_GPL(pv_ops);
+static u64 native_steal_clock(int cpu)
+{
+	return 0;
+}
+
+DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h
index cf3a0fd7c1a7..9aa193e0e8f2 100644
--- a/arch/arm64/include/asm/paravirt.h
+++ b/arch/arm64/include/asm/paravirt.h
@@ -3,23 +3,19 @@
 #define _ASM_ARM64_PARAVIRT_H
 
 #ifdef CONFIG_PARAVIRT
+#include <linux/static_call_types.h>
+
 struct static_key;
 extern struct static_key paravirt_steal_enabled;
 extern struct static_key paravirt_steal_rq_enabled;
 
-struct pv_time_ops {
-	unsigned long long (*steal_clock)(int cpu);
-};
-
-struct paravirt_patch_template {
-	struct pv_time_ops time;
-};
+u64 dummy_steal_clock(int cpu);
 
-extern struct paravirt_patch_template pv_ops;
+DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
 
 static inline u64 paravirt_steal_clock(int cpu)
 {
-	return pv_ops.time.steal_clock(cpu);
+	return static_call(pv_steal_clock)(cpu);
 }
 
 int __init pv_time_init(void);
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
index c07d7a034941..75fed4460407 100644
--- a/arch/arm64/kernel/paravirt.c
+++ b/arch/arm64/kernel/paravirt.c
@@ -18,6 +18,7 @@
 #include <linux/reboot.h>
 #include <linux/slab.h>
 #include <linux/types.h>
+#include <linux/static_call.h>
 
 #include <asm/paravirt.h>
 #include <asm/pvclock-abi.h>
@@ -26,8 +27,12 @@
 struct static_key paravirt_steal_enabled;
 struct static_key paravirt_steal_rq_enabled;
 
-struct paravirt_patch_template pv_ops;
-EXPORT_SYMBOL_GPL(pv_ops);
+static u64 native_steal_clock(int cpu)
+{
+	return 0;
+}
+
+DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
 
 struct pv_time_stolen_time_region {
 	struct pvclock_vcpu_stolen_time *kaddr;
@@ -45,7 +50,7 @@ static int __init parse_no_stealacc(char *arg)
 early_param("no-steal-acc", parse_no_stealacc);
 
 /* return stolen time in ns by asking the hypervisor */
-static u64 pv_steal_clock(int cpu)
+static u64 para_steal_clock(int cpu)
 {
 	struct pv_time_stolen_time_region *reg;
 
@@ -150,7 +155,7 @@ int __init pv_time_init(void)
 	if (ret)
 		return ret;
 
-	pv_ops.time.steal_clock = pv_steal_clock;
+	static_call_update(pv_steal_clock, para_steal_clock);
 
 	static_key_slow_inc(&paravirt_steal_enabled);
 	if (steal_acc)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2792879d398e..107acc403b3b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -777,6 +777,7 @@ if HYPERVISOR_GUEST
 
 config PARAVIRT
 	bool "Enable paravirtualization code"
+	depends on HAVE_STATIC_CALL
 	help
 	  This changes the kernel so it can modify itself when it is run
 	  under a hypervisor, potentially improving performance significantly
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index ccf60a809a17..e7be720062a8 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -63,7 +63,7 @@ typedef int (*hyperv_fill_flush_list_func)(
 static __always_inline void hv_setup_sched_clock(void *sched_clock)
 {
 #ifdef CONFIG_PARAVIRT
-	pv_ops.time.sched_clock = sched_clock;
+	paravirt_set_sched_clock(sched_clock);
 #endif
 }
 
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 4abf110e2243..1e45b46fae84 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -15,11 +15,22 @@
 #include <linux/bug.h>
 #include <linux/types.h>
 #include <linux/cpumask.h>
+#include <linux/static_call_types.h>
 #include <asm/frame.h>
 
-static inline unsigned long long paravirt_sched_clock(void)
+u64 dummy_steal_clock(int cpu);
+u64 dummy_sched_clock(void);
+
+DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
+DECLARE_STATIC_CALL(pv_sched_clock, dummy_sched_clock);
+
+extern bool paravirt_using_native_sched_clock;
+
+void paravirt_set_sched_clock(u64 (*func)(void));
+
+static inline u64 paravirt_sched_clock(void)
 {
-	return PVOP_CALL0(unsigned long long, time.sched_clock);
+	return static_call(pv_sched_clock)();
 }
 
 struct static_key;
@@ -33,7 +44,7 @@ bool pv_is_native_vcpu_is_preempted(void);
 
 static inline u64 paravirt_steal_clock(int cpu)
 {
-	return PVOP_CALL1(u64, time.steal_clock, cpu);
+	return static_call(pv_steal_clock)(cpu);
 }
 
 /* The paravirtualized I/O functions */
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index de87087d3bde..1fff349e4792 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -95,11 +95,6 @@ struct pv_lazy_ops {
 } __no_randomize_layout;
 #endif
 
-struct pv_time_ops {
-	unsigned long long (*sched_clock)(void);
-	unsigned long long (*steal_clock)(int cpu);
-} __no_randomize_layout;
-
 struct pv_cpu_ops {
 	/* hooks for various privileged instructions */
 	void (*io_delay)(void);
@@ -291,7 +286,6 @@ struct pv_lock_ops {
  * what to patch. */
 struct paravirt_patch_template {
 	struct pv_init_ops	init;
-	struct pv_time_ops	time;
 	struct pv_cpu_ops	cpu;
 	struct pv_irq_ops	irq;
 	struct pv_mmu_ops	mmu;
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index c6ede3b3d302..84fb8e3f3d1b 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -27,6 +27,7 @@
 #include <linux/clocksource.h>
 #include <linux/cpu.h>
 #include <linux/reboot.h>
+#include <linux/static_call.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
@@ -336,11 +337,11 @@ static void __init vmware_paravirt_ops_setup(void)
 	vmware_cyc2ns_setup();
 
 	if (vmw_sched_clock)
-		pv_ops.time.sched_clock = vmware_sched_clock;
+		paravirt_set_sched_clock(vmware_sched_clock);
 
 	if (vmware_is_stealclock_available()) {
 		has_steal_clock = true;
-		pv_ops.time.steal_clock = vmware_steal_clock;
+		static_call_update(pv_steal_clock, vmware_steal_clock);
 
 		/* We use reboot notifier only to disable steal clock */
 		register_reboot_notifier(&vmware_pv_reboot_nb);
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 5e78e01ca3b4..351ba99f6009 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -650,7 +650,7 @@ static void __init kvm_guest_init(void)
 
 	if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 		has_steal_clock = 1;
-		pv_ops.time.steal_clock = kvm_steal_clock;
+		static_call_update(pv_steal_clock, kvm_steal_clock);
 	}
 
 	if (pv_tlb_flush_supported()) {
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index aa593743acf6..01e7c1839ace 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -106,7 +106,7 @@ static inline void kvm_sched_clock_init(bool stable)
 	if (!stable)
 		clear_sched_clock_stable();
 	kvm_sched_clock_offset = kvm_clock_read();
-	pv_ops.time.sched_clock = kvm_sched_clock_read;
+	paravirt_set_sched_clock(kvm_sched_clock_read);
 
 	pr_info("kvm-clock: using sched offset of %llu cycles",
 		kvm_sched_clock_offset);
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index c60222ab8ab9..44e5b0fe28cb 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -14,6 +14,7 @@
 #include <linux/highmem.h>
 #include <linux/kprobes.h>
 #include <linux/pgtable.h>
+#include <linux/static_call.h>
 
 #include <asm/bug.h>
 #include <asm/paravirt.h>
@@ -167,6 +168,17 @@ static u64 native_steal_clock(int cpu)
 	return 0;
 }
 
+DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
+DEFINE_STATIC_CALL(pv_sched_clock, native_sched_clock);
+
+bool paravirt_using_native_sched_clock = true;
+
+void paravirt_set_sched_clock(u64 (*func)(void))
+{
+	static_call_update(pv_sched_clock, func);
+	paravirt_using_native_sched_clock = (func == native_sched_clock);
+}
+
 /* These are in entry.S */
 extern void native_iret(void);
 
@@ -272,10 +284,6 @@ struct paravirt_patch_template pv_ops = {
 	/* Init ops. */
 	.init.patch		= native_patch,
 
-	/* Time ops. */
-	.time.sched_clock	= native_sched_clock,
-	.time.steal_clock	= native_steal_clock,
-
 	/* Cpu ops. */
 	.cpu.io_delay		= native_io_delay,
 
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index f70dffc2771f..b6f7853d8077 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -254,7 +254,7 @@ unsigned long long sched_clock(void)
 
 bool using_native_sched_clock(void)
 {
-	return pv_ops.time.sched_clock == native_sched_clock;
+	return paravirt_using_native_sched_clock;
 }
 #else
 unsigned long long
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 91f5b330dcc6..01930e182e99 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -379,11 +379,6 @@ void xen_timer_resume(void)
 	}
 }
 
-static const struct pv_time_ops xen_time_ops __initconst = {
-	.sched_clock = xen_sched_clock,
-	.steal_clock = xen_steal_clock,
-};
-
 static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
 static u64 xen_clock_value_saved;
 
@@ -528,7 +523,8 @@ static void __init xen_time_init(void)
 void __init xen_init_time_ops(void)
 {
 	xen_sched_clock_offset = xen_clocksource_read();
-	pv_ops.time = xen_time_ops;
+	static_call_update(pv_steal_clock, xen_steal_clock);
+	paravirt_set_sched_clock(xen_sched_clock);
 
 	x86_init.timers.timer_init = xen_time_init;
 	x86_init.timers.setup_percpu_clockev = x86_init_noop;
@@ -570,7 +566,8 @@ void __init xen_hvm_init_time_ops(void)
 	}
 
 	xen_sched_clock_offset = xen_clocksource_read();
-	pv_ops.time = xen_time_ops;
+	static_call_update(pv_steal_clock, xen_steal_clock);
+	paravirt_set_sched_clock(xen_sched_clock);
 	x86_init.timers.setup_percpu_clockev = xen_time_init;
 	x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
 
diff --git a/drivers/xen/time.c b/drivers/xen/time.c
index 108edbcbc040..152dd33bb223 100644
--- a/drivers/xen/time.c
+++ b/drivers/xen/time.c
@@ -7,6 +7,7 @@
 #include <linux/math64.h>
 #include <linux/gfp.h>
 #include <linux/slab.h>
+#include <linux/static_call.h>
 
 #include <asm/paravirt.h>
 #include <asm/xen/hypervisor.h>
@@ -175,7 +176,7 @@ void __init xen_time_setup_guest(void)
 	xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
 					VMASST_TYPE_runstate_update_flag);
 
-	pv_ops.time.steal_clock = xen_steal_clock;
+	static_call_update(pv_steal_clock, xen_steal_clock);
 
 	static_key_slow_inc(&paravirt_steal_enabled);
 	if (xen_runstate_remote)
-- 
2.26.2

Re: [PATCH v5 02/12] x86/paravirt: switch time pvops functions to use static_call()

[Boris Ostrovsky]

On 3/8/21 7:28 AM, Juergen Gross wrote:
> --- a/arch/x86/xen/time.c
> +++ b/arch/x86/xen/time.c
> @@ -379,11 +379,6 @@ void xen_timer_resume(void)
>  	}
>  }
>  
> -static const struct pv_time_ops xen_time_ops __initconst = {
> -	.sched_clock = xen_sched_clock,
> -	.steal_clock = xen_steal_clock,
> -};
> -
>  static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
>  static u64 xen_clock_value_saved;
>  
> @@ -528,7 +523,8 @@ static void __init xen_time_init(void)
>  void __init xen_init_time_ops(void)
>  {
>  	xen_sched_clock_offset = xen_clocksource_read();
> -	pv_ops.time = xen_time_ops;
> +	static_call_update(pv_steal_clock, xen_steal_clock);
> +	paravirt_set_sched_clock(xen_sched_clock);
>  
>  	x86_init.timers.timer_init = xen_time_init;
>  	x86_init.timers.setup_percpu_clockev = x86_init_noop;
> @@ -570,7 +566,8 @@ void __init xen_hvm_init_time_ops(void)
>  	}
>  
>  	xen_sched_clock_offset = xen_clocksource_read();
> -	pv_ops.time = xen_time_ops;
> +	static_call_update(pv_steal_clock, xen_steal_clock);
> +	paravirt_set_sched_clock(xen_sched_clock);
>  	x86_init.timers.setup_percpu_clockev = xen_time_init;
>  	x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;


There is a bunch of stuff that's common between the two cases so it can be factored out.


>  
> diff --git a/drivers/xen/time.c b/drivers/xen/time.c
> index 108edbcbc040..152dd33bb223 100644
> --- a/drivers/xen/time.c
> +++ b/drivers/xen/time.c
> @@ -7,6 +7,7 @@
>  #include <linux/math64.h>
>  #include <linux/gfp.h>
>  #include <linux/slab.h>
> +#include <linux/static_call.h>
>  
>  #include <asm/paravirt.h>
>  #include <asm/xen/hypervisor.h>
> @@ -175,7 +176,7 @@ void __init xen_time_setup_guest(void)
>  	xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
>  					VMASST_TYPE_runstate_update_flag);
>  
> -	pv_ops.time.steal_clock = xen_steal_clock;
> +	static_call_update(pv_steal_clock, xen_steal_clock);
>  


Do we actually need this? We've already set this up in xen_init_time_ops(). (But maybe for ARM).


-boris


>  	static_key_slow_inc(&paravirt_steal_enabled);
>  	if (xen_runstate_remote)

Re: [PATCH v5 02/12] x86/paravirt: switch time pvops functions to use static_call()

[Jürgen Groß]

[-- Attachment #1.1.1: Type: text/plain, Size: 2303 bytes --]

On 08.03.21 18:00, Boris Ostrovsky wrote:
> 
> On 3/8/21 7:28 AM, Juergen Gross wrote:
>> --- a/arch/x86/xen/time.c
>> +++ b/arch/x86/xen/time.c
>> @@ -379,11 +379,6 @@ void xen_timer_resume(void)
>>   	}
>>   }
>>   
>> -static const struct pv_time_ops xen_time_ops __initconst = {
>> -	.sched_clock = xen_sched_clock,
>> -	.steal_clock = xen_steal_clock,
>> -};
>> -
>>   static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
>>   static u64 xen_clock_value_saved;
>>   
>> @@ -528,7 +523,8 @@ static void __init xen_time_init(void)
>>   void __init xen_init_time_ops(void)
>>   {
>>   	xen_sched_clock_offset = xen_clocksource_read();
>> -	pv_ops.time = xen_time_ops;
>> +	static_call_update(pv_steal_clock, xen_steal_clock);
>> +	paravirt_set_sched_clock(xen_sched_clock);
>>   
>>   	x86_init.timers.timer_init = xen_time_init;
>>   	x86_init.timers.setup_percpu_clockev = x86_init_noop;
>> @@ -570,7 +566,8 @@ void __init xen_hvm_init_time_ops(void)
>>   	}
>>   
>>   	xen_sched_clock_offset = xen_clocksource_read();
>> -	pv_ops.time = xen_time_ops;
>> +	static_call_update(pv_steal_clock, xen_steal_clock);
>> +	paravirt_set_sched_clock(xen_sched_clock);
>>   	x86_init.timers.setup_percpu_clockev = xen_time_init;
>>   	x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
> 
> 
> There is a bunch of stuff that's common between the two cases so it can be factored out.

Yes.

> 
> 
>>   
>> diff --git a/drivers/xen/time.c b/drivers/xen/time.c
>> index 108edbcbc040..152dd33bb223 100644
>> --- a/drivers/xen/time.c
>> +++ b/drivers/xen/time.c
>> @@ -7,6 +7,7 @@
>>   #include <linux/math64.h>
>>   #include <linux/gfp.h>
>>   #include <linux/slab.h>
>> +#include <linux/static_call.h>
>>   
>>   #include <asm/paravirt.h>
>>   #include <asm/xen/hypervisor.h>
>> @@ -175,7 +176,7 @@ void __init xen_time_setup_guest(void)
>>   	xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
>>   					VMASST_TYPE_runstate_update_flag);
>>   
>> -	pv_ops.time.steal_clock = xen_steal_clock;
>> +	static_call_update(pv_steal_clock, xen_steal_clock);
>>   
> 
> 
> Do we actually need this? We've already set this up in xen_init_time_ops(). (But maybe for ARM).

Correct. Arm needs this.


Juergen

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[PATCH v5 03/12] x86/alternative: drop feature parameter from ALTINSTR_REPLACEMENT()

[Juergen Gross]

The macro ALTINSTR_REPLACEMENT() doesn't make use of the feature
parameter, so drop it.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V5:
- new patch
---
 arch/x86/include/asm/alternative.h | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 13adca37c99a..5753fb2ac489 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -150,7 +150,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	" .byte " alt_rlen(num) "\n"			/* replacement len */ \
 	" .byte " alt_pad_len "\n"			/* pad len */
 
-#define ALTINSTR_REPLACEMENT(newinstr, feature, num)	/* replacement */	\
+#define ALTINSTR_REPLACEMENT(newinstr, num)		/* replacement */	\
 	"# ALT: replacement " #num "\n"						\
 	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
 
@@ -161,7 +161,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_ENTRY(feature, 1)					\
 	".popsection\n"							\
 	".pushsection .altinstr_replacement, \"ax\"\n"			\
-	ALTINSTR_REPLACEMENT(newinstr, feature, 1)			\
+	ALTINSTR_REPLACEMENT(newinstr, 1)				\
 	".popsection\n"
 
 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
@@ -171,8 +171,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_ENTRY(feature2, 2)					\
 	".popsection\n"							\
 	".pushsection .altinstr_replacement, \"ax\"\n"			\
-	ALTINSTR_REPLACEMENT(newinstr1, feature1, 1)			\
-	ALTINSTR_REPLACEMENT(newinstr2, feature2, 2)			\
+	ALTINSTR_REPLACEMENT(newinstr1, 1)				\
+	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
 	".popsection\n"
 
 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
@@ -183,9 +183,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_ENTRY(feat3, 3)						\
 	".popsection\n"								\
 	".pushsection .altinstr_replacement, \"ax\"\n"				\
-	ALTINSTR_REPLACEMENT(newinsn1, feat1, 1)				\
-	ALTINSTR_REPLACEMENT(newinsn2, feat2, 2)				\
-	ALTINSTR_REPLACEMENT(newinsn3, feat3, 3)				\
+	ALTINSTR_REPLACEMENT(newinsn1, 1)					\
+	ALTINSTR_REPLACEMENT(newinsn2, 2)					\
+	ALTINSTR_REPLACEMENT(newinsn3, 3)					\
 	".popsection\n"
 
 /*
-- 
2.26.2

[PATCH v5 04/12] x86/alternative: support not-feature

[Juergen Gross]

Add support for alternative patching for the case a feature is not
present on the current cpu.

For this purpose add a flag byte to struct alt_instr adding the
information that the inverted feature should be used.

For users of ALTERNATIVE() and friends an inverted feature is specified
by negating it, e.g.:

ALTERNATIVE(old, new, ~feature)

This requires adapting the objtool information for struct alt_instr.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V5:
- split off from next patch
- reworked to use flag byte (Boris Petkov)
---
 arch/x86/include/asm/alternative-asm.h        | 6 ++++++
 arch/x86/include/asm/alternative.h            | 8 ++++++++
 arch/x86/include/asm/cpufeature.h             | 2 ++
 arch/x86/kernel/alternative.c                 | 5 +++--
 tools/objtool/arch/x86/include/arch/special.h | 6 +++---
 5 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h
index 464034db299f..9a1763550217 100644
--- a/arch/x86/include/asm/alternative-asm.h
+++ b/arch/x86/include/asm/alternative-asm.h
@@ -39,7 +39,13 @@
 .macro altinstruction_entry orig alt feature orig_len alt_len pad_len
 	.long \orig - .
 	.long \alt - .
+	.iflt \feature
+	.word ~(\feature)
+	.byte 1
+	.else
 	.word \feature
+	.byte 0
+	.endif
 	.byte \orig_len
 	.byte \alt_len
 	.byte \pad_len
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 5753fb2ac489..b9749cf21ada 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -59,6 +59,8 @@ struct alt_instr {
 	s32 instr_offset;	/* original instruction */
 	s32 repl_offset;	/* offset to replacement instruction */
 	u16 cpuid;		/* cpuid bit set for replacement */
+	u8  flag;		/* flag byte */
+#define ALTINSTR_FLAG_INV	0x01
 	u8  instrlen;		/* length of original instruction */
 	u8  replacementlen;	/* length of new instruction */
 	u8  padlen;		/* length of build-time padding */
@@ -145,7 +147,13 @@ static inline int alternatives_text_reserved(void *start, void *end)
 #define ALTINSTR_ENTRY(feature, num)					      \
 	" .long 661b - .\n"				/* label           */ \
 	" .long " b_replacement(num)"f - .\n"		/* new instruction */ \
+	" .iflt " __stringify(feature) "\n"		/* inverted?       */ \
+	" .word ~(" __stringify(feature) ")\n"		/* feature bit     */ \
+	" .byte " __stringify(ALTINSTR_FLAG_INV) "\n"	/* flag byte       */ \
+	" .else\n"							      \
 	" .word " __stringify(feature) "\n"		/* feature bit     */ \
+	" .byte 0\n"					/* flag byte       */ \
+	" .endif\n"							      \
 	" .byte " alt_total_slen "\n"			/* source len      */ \
 	" .byte " alt_rlen(num) "\n"			/* replacement len */ \
 	" .byte " alt_pad_len "\n"			/* pad len */
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 1728d4ce5730..f060d3186ee4 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -184,6 +184,7 @@ static __always_inline bool _static_cpu_has(u16 bit)
 		 " .long 1b - .\n"		/* src offset */
 		 " .long 4f - .\n"		/* repl offset */
 		 " .word %P[always]\n"		/* always replace */
+		 " .byte 0\n"			/* flag byte */
 		 " .byte 3b - 1b\n"		/* src len */
 		 " .byte 5f - 4f\n"		/* repl len */
 		 " .byte 3b - 2b\n"		/* pad len */
@@ -196,6 +197,7 @@ static __always_inline bool _static_cpu_has(u16 bit)
 		 " .long 1b - .\n"		/* src offset */
 		 " .long 0\n"			/* no replacement */
 		 " .word %P[feature]\n"		/* feature bit */
+		 " .byte 0\n"			/* flag byte */
 		 " .byte 3b - 1b\n"		/* src len */
 		 " .byte 0\n"			/* repl len */
 		 " .byte 0\n"			/* pad len */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 8d778e46725d..1296a90aa5b8 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -393,14 +393,15 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
 		replacement = (u8 *)&a->repl_offset + a->repl_offset;
 		BUG_ON(a->instrlen > sizeof(insn_buff));
 		BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
-		if (!boot_cpu_has(a->cpuid)) {
+		if (!boot_cpu_has(a->cpuid) == !(a->flag & ALTINSTR_FLAG_INV)) {
 			if (a->padlen > 1)
 				optimize_nops(a, instr);
 
 			continue;
 		}
 
-		DPRINTK("feat: %d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
+		DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
+			(a->flag & ALTINSTR_FLAG_INV) ? "~" : "",
 			a->cpuid >> 5,
 			a->cpuid & 0x1f,
 			instr, instr, a->instrlen,
diff --git a/tools/objtool/arch/x86/include/arch/special.h b/tools/objtool/arch/x86/include/arch/special.h
index d818b2bffa02..afde39063963 100644
--- a/tools/objtool/arch/x86/include/arch/special.h
+++ b/tools/objtool/arch/x86/include/arch/special.h
@@ -10,11 +10,11 @@
 #define JUMP_ORIG_OFFSET	0
 #define JUMP_NEW_OFFSET		4
 
-#define ALT_ENTRY_SIZE		13
+#define ALT_ENTRY_SIZE		14
 #define ALT_ORIG_OFFSET		0
 #define ALT_NEW_OFFSET		4
 #define ALT_FEATURE_OFFSET	8
-#define ALT_ORIG_LEN_OFFSET	10
-#define ALT_NEW_LEN_OFFSET	11
+#define ALT_ORIG_LEN_OFFSET	11
+#define ALT_NEW_LEN_OFFSET	12
 
 #endif /* _X86_ARCH_SPECIAL_H */
-- 
2.26.2

[PATCH v5 05/12] x86/alternative: support ALTERNATIVE_TERNARY

[Juergen Gross]

Add ALTERNATIVE_TERNARY support for replacing an initial instruction
with either of two instructions depending on a feature:

  ALTERNATIVE_TERNARY "default_instr", FEATURE_NR,
                      "feature_on_instr", "feature_off_instr"

which will start with "default_instr" and at patch time will, depending
on FEATURE_NR being set or not, patch that with either
"feature_on_instr" or "feature_off_instr".

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- new patch
V4:
- use X86_FEATURE_ALWAYS instead of negated feature (Boris Petkov)
- unfortunately this isn't enough to get rid of the "not feature"
  support, as this is needed in the patch "x86/paravirt: switch
  functions with custom code to ALTERNATIVE", too
V5:
- carve out the "not feature" part
---
 arch/x86/include/asm/alternative-asm.h | 4 ++++
 arch/x86/include/asm/alternative.h     | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h
index 9a1763550217..ba0aad81d3bb 100644
--- a/arch/x86/include/asm/alternative-asm.h
+++ b/arch/x86/include/asm/alternative-asm.h
@@ -115,6 +115,10 @@
 	.popsection
 .endm
 
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)	\
+	ALTERNATIVE_2 oldinstr, newinstr2, X86_FEATURE_ALWAYS,		\
+	newinstr1, feature
+
 #endif  /*  __ASSEMBLY__  */
 
 #endif /* _ASM_X86_ALTERNATIVE_ASM_H */
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index b9749cf21ada..693991f8fe89 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -183,6 +183,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
 	".popsection\n"
 
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)	\
+	ALTERNATIVE_2(oldinstr, newinstr2, X86_FEATURE_ALWAYS, newinstr1, feature)
+
 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
 	OLDINSTR_3(oldinsn, 1, 2, 3)						\
 	".pushsection .altinstructions,\"a\"\n"					\
@@ -214,6 +217,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
 	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
 
+#define alternative_ternary(oldinstr, feature, newinstr1, newinstr2)	\
+	asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) ::: "memory")
+
 /*
  * Alternative inline assembly with input.
  *
-- 
2.26.2

[PATCH v5 06/12] x86: add new features for paravirt patching

[Juergen Gross]

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 alternative patching.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- add comment (Boris Petkov)
- no negative features (Boris Petkov)
V4:
- move paravirt_set_cap() to paravirt-spinlocks.c
---
 arch/x86/include/asm/cpufeatures.h   |  2 ++
 arch/x86/include/asm/paravirt.h      | 10 ++++++++++
 arch/x86/kernel/alternative.c        | 30 ++++++++++++++++++++++++++--
 arch/x86/kernel/paravirt-spinlocks.c |  9 +++++++++
 4 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index cc96e26d69f7..b440c950246d 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -236,6 +236,8 @@
 #define X86_FEATURE_EPT_AD		( 8*32+17) /* Intel Extended Page Table access-dirty bit */
 #define X86_FEATURE_VMCALL		( 8*32+18) /* "" Hypervisor supports the VMCALL instruction */
 #define X86_FEATURE_VMW_VMMCALL		( 8*32+19) /* "" VMware prefers VMMCALL hypercall instruction */
+#define X86_FEATURE_PVUNLOCK		( 8*32+20) /* "" PV unlock function */
+#define X86_FEATURE_VCPUPREEMPT		( 8*32+21) /* "" PV vcpu_is_preempted function */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
 #define X86_FEATURE_FSGSBASE		( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 1e45b46fae84..8c354099d9c3 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -47,6 +47,10 @@ static inline u64 paravirt_steal_clock(int cpu)
 	return static_call(pv_steal_clock)(cpu);
 }
 
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+void __init paravirt_set_cap(void);
+#endif
+
 /* The paravirtualized I/O functions */
 static inline void slow_down_io(void)
 {
@@ -811,5 +815,11 @@ static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
 {
 }
 #endif
+
+#ifndef CONFIG_PARAVIRT_SPINLOCKS
+static inline void paravirt_set_cap(void)
+{
+}
+#endif
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_X86_PARAVIRT_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 1296a90aa5b8..ab9ad729fc5a 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;
 
@@ -724,6 +725,33 @@ 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
@@ -742,8 +770,6 @@ void __init alternative_instructions(void)
 	}
 #endif
 
-	apply_paravirt(__parainstructions, __parainstructions_end);
-
 	restart_nmi();
 	alternatives_patched = 1;
 }
diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
index 4f75d0cf6305..9e1ea99ad9df 100644
--- a/arch/x86/kernel/paravirt-spinlocks.c
+++ b/arch/x86/kernel/paravirt-spinlocks.c
@@ -32,3 +32,12 @@ bool pv_is_native_vcpu_is_preempted(void)
 	return pv_ops.lock.vcpu_is_preempted.func ==
 		__raw_callee_save___native_vcpu_is_preempted;
 }
+
+void __init paravirt_set_cap(void)
+{
+	if (!pv_is_native_spin_unlock())
+		setup_force_cpu_cap(X86_FEATURE_PVUNLOCK);
+
+	if (!pv_is_native_vcpu_is_preempted())
+		setup_force_cpu_cap(X86_FEATURE_VCPUPREEMPT);
+}
-- 
2.26.2

[PATCH v5 07/12] x86/paravirt: remove no longer needed 32-bit pvops cruft

[Juergen Gross]

PVOP_VCALL4() is only used for Xen PV, while PVOP_CALL4() isn't used
at all. Keep PVOP_CALL4() for 64 bits due to symmetry reasons.

This allows to remove the 32-bit definitions of those macros leading
to a substantial simplification of the paravirt macros, as those were
the only ones needing non-empty "pre" and "post" parameters.

PVOP_CALLEE2() and PVOP_VCALLEE2() are used nowhere, so remove them.

Another no longer needed case is special handling of return types
larger than unsigned long. Replace that with a BUILD_BUG_ON().

DISABLE_INTERRUPTS() is used in 32-bit code only, so it can just be
replaced by cli.

INTERRUPT_RETURN in 32-bit code can be replaced by iret.

ENABLE_INTERRUPTS is used nowhere, so it can be removed.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/entry/entry_32.S             |   4 +-
 arch/x86/include/asm/irqflags.h       |   5 --
 arch/x86/include/asm/paravirt.h       |  35 +-------
 arch/x86/include/asm/paravirt_types.h | 112 ++++++++------------------
 arch/x86/kernel/asm-offsets.c         |   2 -
 5 files changed, 35 insertions(+), 123 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index df8c017e6161..765487e57d6e 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -430,7 +430,7 @@
 	 * will soon execute iret and the tracer was already set to
 	 * the irqstate after the IRET:
 	 */
-	DISABLE_INTERRUPTS(CLBR_ANY)
+	cli
 	lss	(%esp), %esp			/* switch to espfix segment */
 .Lend_\@:
 #endif /* CONFIG_X86_ESPFIX32 */
@@ -1077,7 +1077,7 @@ restore_all_switch_stack:
 	 * when returning from IPI handler and when returning from
 	 * scheduler to user-space.
 	 */
-	INTERRUPT_RETURN
+	iret
 
 .section .fixup, "ax"
 SYM_CODE_START(asm_iret_error)
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index 144d70ea4393..a0efbcd24b86 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -109,9 +109,6 @@ static __always_inline unsigned long arch_local_irq_save(void)
 }
 #else
 
-#define ENABLE_INTERRUPTS(x)	sti
-#define DISABLE_INTERRUPTS(x)	cli
-
 #ifdef CONFIG_X86_64
 #ifdef CONFIG_DEBUG_ENTRY
 #define SAVE_FLAGS(x)		pushfq; popq %rax
@@ -119,8 +116,6 @@ static __always_inline unsigned long arch_local_irq_save(void)
 
 #define INTERRUPT_RETURN	jmp native_iret
 
-#else
-#define INTERRUPT_RETURN		iret
 #endif
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 8c354099d9c3..c6496a82fad1 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -721,6 +721,7 @@ extern void default_banner(void);
 	.if ((~(set)) & mask); pop %reg; .endif
 
 #ifdef CONFIG_X86_64
+#ifdef CONFIG_PARAVIRT_XXL
 
 #define PV_SAVE_REGS(set)			\
 	COND_PUSH(set, CLBR_RAX, rax);		\
@@ -746,46 +747,12 @@ extern void default_banner(void);
 #define PARA_PATCH(off)		((off) / 8)
 #define PARA_SITE(ptype, ops)	_PVSITE(ptype, ops, .quad, 8)
 #define PARA_INDIRECT(addr)	*addr(%rip)
-#else
-#define PV_SAVE_REGS(set)			\
-	COND_PUSH(set, CLBR_EAX, eax);		\
-	COND_PUSH(set, CLBR_EDI, edi);		\
-	COND_PUSH(set, CLBR_ECX, ecx);		\
-	COND_PUSH(set, CLBR_EDX, edx)
-#define PV_RESTORE_REGS(set)			\
-	COND_POP(set, CLBR_EDX, edx);		\
-	COND_POP(set, CLBR_ECX, ecx);		\
-	COND_POP(set, CLBR_EDI, edi);		\
-	COND_POP(set, CLBR_EAX, eax)
-
-#define PARA_PATCH(off)		((off) / 4)
-#define PARA_SITE(ptype, ops)	_PVSITE(ptype, ops, .long, 4)
-#define PARA_INDIRECT(addr)	*%cs:addr
-#endif
 
-#ifdef CONFIG_PARAVIRT_XXL
 #define INTERRUPT_RETURN						\
 	PARA_SITE(PARA_PATCH(PV_CPU_iret),				\
 		  ANNOTATE_RETPOLINE_SAFE;				\
 		  jmp PARA_INDIRECT(pv_ops+PV_CPU_iret);)
 
-#define DISABLE_INTERRUPTS(clobbers)					\
-	PARA_SITE(PARA_PATCH(PV_IRQ_irq_disable),			\
-		  PV_SAVE_REGS(clobbers | CLBR_CALLEE_SAVE);		\
-		  ANNOTATE_RETPOLINE_SAFE;				\
-		  call PARA_INDIRECT(pv_ops+PV_IRQ_irq_disable);	\
-		  PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);)
-
-#define ENABLE_INTERRUPTS(clobbers)					\
-	PARA_SITE(PARA_PATCH(PV_IRQ_irq_enable),			\
-		  PV_SAVE_REGS(clobbers | CLBR_CALLEE_SAVE);		\
-		  ANNOTATE_RETPOLINE_SAFE;				\
-		  call PARA_INDIRECT(pv_ops+PV_IRQ_irq_enable);		\
-		  PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);)
-#endif
-
-#ifdef CONFIG_X86_64
-#ifdef CONFIG_PARAVIRT_XXL
 #ifdef CONFIG_DEBUG_ENTRY
 #define SAVE_FLAGS(clobbers)                                        \
 	PARA_SITE(PARA_PATCH(PV_IRQ_save_fl),			    \
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 1fff349e4792..42f9eef84131 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -470,55 +470,34 @@ int paravirt_disable_iospace(void);
 	})
 
 
-#define ____PVOP_CALL(rettype, op, clbr, call_clbr, extra_clbr,		\
-		      pre, post, ...)					\
+#define ____PVOP_CALL(rettype, op, clbr, call_clbr, extra_clbr, ...)	\
 	({								\
-		rettype __ret;						\
 		PVOP_CALL_ARGS;						\
 		PVOP_TEST_NULL(op);					\
-		/* This is 32-bit specific, but is okay in 64-bit */	\
-		/* since this condition will never hold */		\
-		if (sizeof(rettype) > sizeof(unsigned long)) {		\
-			asm volatile(pre				\
-				     paravirt_alt(PARAVIRT_CALL)	\
-				     post				\
-				     : call_clbr, ASM_CALL_CONSTRAINT	\
-				     : paravirt_type(op),		\
-				       paravirt_clobber(clbr),		\
-				       ##__VA_ARGS__			\
-				     : "memory", "cc" extra_clbr);	\
-			__ret = (rettype)((((u64)__edx) << 32) | __eax); \
-		} else {						\
-			asm volatile(pre				\
-				     paravirt_alt(PARAVIRT_CALL)	\
-				     post				\
-				     : call_clbr, ASM_CALL_CONSTRAINT	\
-				     : paravirt_type(op),		\
-				       paravirt_clobber(clbr),		\
-				       ##__VA_ARGS__			\
-				     : "memory", "cc" extra_clbr);	\
-			__ret = (rettype)(__eax & PVOP_RETMASK(rettype));	\
-		}							\
-		__ret;							\
+		BUILD_BUG_ON(sizeof(rettype) > sizeof(unsigned long));	\
+		asm volatile(paravirt_alt(PARAVIRT_CALL)		\
+			     : call_clbr, ASM_CALL_CONSTRAINT		\
+			     : paravirt_type(op),			\
+			       paravirt_clobber(clbr),			\
+			       ##__VA_ARGS__				\
+			     : "memory", "cc" extra_clbr);		\
+		(rettype)(__eax & PVOP_RETMASK(rettype));		\
 	})
 
-#define __PVOP_CALL(rettype, op, pre, post, ...)			\
+#define __PVOP_CALL(rettype, op, ...)					\
 	____PVOP_CALL(rettype, op, CLBR_ANY, PVOP_CALL_CLOBBERS,	\
-		      EXTRA_CLOBBERS, pre, post, ##__VA_ARGS__)
+		      EXTRA_CLOBBERS, ##__VA_ARGS__)
 
-#define __PVOP_CALLEESAVE(rettype, op, pre, post, ...)			\
+#define __PVOP_CALLEESAVE(rettype, op, ...)				\
 	____PVOP_CALL(rettype, op.func, CLBR_RET_REG,			\
-		      PVOP_CALLEE_CLOBBERS, ,				\
-		      pre, post, ##__VA_ARGS__)
+		      PVOP_CALLEE_CLOBBERS, , ##__VA_ARGS__)
 
 
-#define ____PVOP_VCALL(op, clbr, call_clbr, extra_clbr, pre, post, ...)	\
+#define ____PVOP_VCALL(op, clbr, call_clbr, extra_clbr, ...)		\
 	({								\
 		PVOP_VCALL_ARGS;					\
 		PVOP_TEST_NULL(op);					\
-		asm volatile(pre					\
-			     paravirt_alt(PARAVIRT_CALL)		\
-			     post					\
+		asm volatile(paravirt_alt(PARAVIRT_CALL)		\
 			     : call_clbr, ASM_CALL_CONSTRAINT		\
 			     : paravirt_type(op),			\
 			       paravirt_clobber(clbr),			\
@@ -526,84 +505,57 @@ int paravirt_disable_iospace(void);
 			     : "memory", "cc" extra_clbr);		\
 	})
 
-#define __PVOP_VCALL(op, pre, post, ...)				\
+#define __PVOP_VCALL(op, ...)						\
 	____PVOP_VCALL(op, CLBR_ANY, PVOP_VCALL_CLOBBERS,		\
-		       VEXTRA_CLOBBERS,					\
-		       pre, post, ##__VA_ARGS__)
+		       VEXTRA_CLOBBERS, ##__VA_ARGS__)
 
-#define __PVOP_VCALLEESAVE(op, pre, post, ...)				\
+#define __PVOP_VCALLEESAVE(op, ...)					\
 	____PVOP_VCALL(op.func, CLBR_RET_REG,				\
-		      PVOP_VCALLEE_CLOBBERS, ,				\
-		      pre, post, ##__VA_ARGS__)
+		      PVOP_VCALLEE_CLOBBERS, , ##__VA_ARGS__)
 
 
 
 #define PVOP_CALL0(rettype, op)						\
-	__PVOP_CALL(rettype, op, "", "")
+	__PVOP_CALL(rettype, op)
 #define PVOP_VCALL0(op)							\
-	__PVOP_VCALL(op, "", "")
+	__PVOP_VCALL(op)
 
 #define PVOP_CALLEE0(rettype, op)					\
-	__PVOP_CALLEESAVE(rettype, op, "", "")
+	__PVOP_CALLEESAVE(rettype, op)
 #define PVOP_VCALLEE0(op)						\
-	__PVOP_VCALLEESAVE(op, "", "")
+	__PVOP_VCALLEESAVE(op)
 
 
 #define PVOP_CALL1(rettype, op, arg1)					\
-	__PVOP_CALL(rettype, op, "", "", PVOP_CALL_ARG1(arg1))
+	__PVOP_CALL(rettype, op, PVOP_CALL_ARG1(arg1))
 #define PVOP_VCALL1(op, arg1)						\
-	__PVOP_VCALL(op, "", "", PVOP_CALL_ARG1(arg1))
+	__PVOP_VCALL(op, PVOP_CALL_ARG1(arg1))
 
 #define PVOP_CALLEE1(rettype, op, arg1)					\
-	__PVOP_CALLEESAVE(rettype, op, "", "", PVOP_CALL_ARG1(arg1))
+	__PVOP_CALLEESAVE(rettype, op, PVOP_CALL_ARG1(arg1))
 #define PVOP_VCALLEE1(op, arg1)						\
-	__PVOP_VCALLEESAVE(op, "", "", PVOP_CALL_ARG1(arg1))
+	__PVOP_VCALLEESAVE(op, PVOP_CALL_ARG1(arg1))
 
 
 #define PVOP_CALL2(rettype, op, arg1, arg2)				\
-	__PVOP_CALL(rettype, op, "", "", PVOP_CALL_ARG1(arg1),		\
-		    PVOP_CALL_ARG2(arg2))
+	__PVOP_CALL(rettype, op, PVOP_CALL_ARG1(arg1), PVOP_CALL_ARG2(arg2))
 #define PVOP_VCALL2(op, arg1, arg2)					\
-	__PVOP_VCALL(op, "", "", PVOP_CALL_ARG1(arg1),			\
-		     PVOP_CALL_ARG2(arg2))
-
-#define PVOP_CALLEE2(rettype, op, arg1, arg2)				\
-	__PVOP_CALLEESAVE(rettype, op, "", "", PVOP_CALL_ARG1(arg1),	\
-			  PVOP_CALL_ARG2(arg2))
-#define PVOP_VCALLEE2(op, arg1, arg2)					\
-	__PVOP_VCALLEESAVE(op, "", "", PVOP_CALL_ARG1(arg1),		\
-			   PVOP_CALL_ARG2(arg2))
-
+	__PVOP_VCALL(op, PVOP_CALL_ARG1(arg1), PVOP_CALL_ARG2(arg2))
 
 #define PVOP_CALL3(rettype, op, arg1, arg2, arg3)			\
-	__PVOP_CALL(rettype, op, "", "", PVOP_CALL_ARG1(arg1),		\
+	__PVOP_CALL(rettype, op, PVOP_CALL_ARG1(arg1),			\
 		    PVOP_CALL_ARG2(arg2), PVOP_CALL_ARG3(arg3))
 #define PVOP_VCALL3(op, arg1, arg2, arg3)				\
-	__PVOP_VCALL(op, "", "", PVOP_CALL_ARG1(arg1),			\
+	__PVOP_VCALL(op, PVOP_CALL_ARG1(arg1),				\
 		     PVOP_CALL_ARG2(arg2), PVOP_CALL_ARG3(arg3))
 
-/* This is the only difference in x86_64. We can make it much simpler */
-#ifdef CONFIG_X86_32
 #define PVOP_CALL4(rettype, op, arg1, arg2, arg3, arg4)			\
 	__PVOP_CALL(rettype, op,					\
-		    "push %[_arg4];", "lea 4(%%esp),%%esp;",		\
-		    PVOP_CALL_ARG1(arg1), PVOP_CALL_ARG2(arg2),		\
-		    PVOP_CALL_ARG3(arg3), [_arg4] "mr" ((u32)(arg4)))
-#define PVOP_VCALL4(op, arg1, arg2, arg3, arg4)				\
-	__PVOP_VCALL(op,						\
-		    "push %[_arg4];", "lea 4(%%esp),%%esp;",		\
-		    "0" ((u32)(arg1)), "1" ((u32)(arg2)),		\
-		    "2" ((u32)(arg3)), [_arg4] "mr" ((u32)(arg4)))
-#else
-#define PVOP_CALL4(rettype, op, arg1, arg2, arg3, arg4)			\
-	__PVOP_CALL(rettype, op, "", "",				\
 		    PVOP_CALL_ARG1(arg1), PVOP_CALL_ARG2(arg2),		\
 		    PVOP_CALL_ARG3(arg3), PVOP_CALL_ARG4(arg4))
 #define PVOP_VCALL4(op, arg1, arg2, arg3, arg4)				\
-	__PVOP_VCALL(op, "", "",					\
-		     PVOP_CALL_ARG1(arg1), PVOP_CALL_ARG2(arg2),	\
+	__PVOP_VCALL(op, PVOP_CALL_ARG1(arg1), PVOP_CALL_ARG2(arg2),	\
 		     PVOP_CALL_ARG3(arg3), PVOP_CALL_ARG4(arg4))
-#endif
 
 /* Lazy mode for batching updates / context switch */
 enum paravirt_lazy_mode {
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 60b9f42ce3c1..736508004b30 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -63,8 +63,6 @@ static void __used common(void)
 
 #ifdef CONFIG_PARAVIRT_XXL
 	BLANK();
-	OFFSET(PV_IRQ_irq_disable, paravirt_patch_template, irq.irq_disable);
-	OFFSET(PV_IRQ_irq_enable, paravirt_patch_template, irq.irq_enable);
 	OFFSET(PV_CPU_iret, paravirt_patch_template, cpu.iret);
 #endif
 
-- 
2.26.2

[PATCH v5 08/12] x86/paravirt: simplify paravirt macros

[Juergen Gross]

The central pvops call macros ____PVOP_CALL() and ____PVOP_VCALL() are
looking very similar now.

The main differences are using PVOP_VCALL_ARGS or PVOP_CALL_ARGS, which
are identical, and the return value handling.

So drop PVOP_VCALL_ARGS and instead of ____PVOP_VCALL() just use
(void)____PVOP_CALL(long, ...).

Note that it isn't easily possible to just redefine ____PVOP_VCALL()
to use ____PVOP_CALL() instead, as this would require further hiding of
commas in macro parameters.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- new patch
V4:
- fix build warnings with clang (kernel test robot)
---
 arch/x86/include/asm/paravirt_types.h | 41 ++++++++-------------------
 1 file changed, 12 insertions(+), 29 deletions(-)

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 42f9eef84131..45bd21647dd8 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -408,11 +408,9 @@ int paravirt_disable_iospace(void);
  * makes sure the incoming and outgoing types are always correct.
  */
 #ifdef CONFIG_X86_32
-#define PVOP_VCALL_ARGS							\
+#define PVOP_CALL_ARGS							\
 	unsigned long __eax = __eax, __edx = __edx, __ecx = __ecx;
 
-#define PVOP_CALL_ARGS			PVOP_VCALL_ARGS
-
 #define PVOP_CALL_ARG1(x)		"a" ((unsigned long)(x))
 #define PVOP_CALL_ARG2(x)		"d" ((unsigned long)(x))
 #define PVOP_CALL_ARG3(x)		"c" ((unsigned long)(x))
@@ -428,12 +426,10 @@ int paravirt_disable_iospace(void);
 #define VEXTRA_CLOBBERS
 #else  /* CONFIG_X86_64 */
 /* [re]ax isn't an arg, but the return val */
-#define PVOP_VCALL_ARGS						\
+#define PVOP_CALL_ARGS						\
 	unsigned long __edi = __edi, __esi = __esi,		\
 		__edx = __edx, __ecx = __ecx, __eax = __eax;
 
-#define PVOP_CALL_ARGS		PVOP_VCALL_ARGS
-
 #define PVOP_CALL_ARG1(x)		"D" ((unsigned long)(x))
 #define PVOP_CALL_ARG2(x)		"S" ((unsigned long)(x))
 #define PVOP_CALL_ARG3(x)		"d" ((unsigned long)(x))
@@ -458,59 +454,46 @@ int paravirt_disable_iospace(void);
 #define PVOP_TEST_NULL(op)	((void)pv_ops.op)
 #endif
 
-#define PVOP_RETMASK(rettype)						\
+#define PVOP_RETVAL(rettype)						\
 	({	unsigned long __mask = ~0UL;				\
+		BUILD_BUG_ON(sizeof(rettype) > sizeof(unsigned long));	\
 		switch (sizeof(rettype)) {				\
 		case 1: __mask =       0xffUL; break;			\
 		case 2: __mask =     0xffffUL; break;			\
 		case 4: __mask = 0xffffffffUL; break;			\
 		default: break;						\
 		}							\
-		__mask;							\
+		__mask & __eax;						\
 	})
 
 
-#define ____PVOP_CALL(rettype, op, clbr, call_clbr, extra_clbr, ...)	\
+#define ____PVOP_CALL(ret, op, clbr, call_clbr, extra_clbr, ...)	\
 	({								\
 		PVOP_CALL_ARGS;						\
 		PVOP_TEST_NULL(op);					\
-		BUILD_BUG_ON(sizeof(rettype) > sizeof(unsigned long));	\
 		asm volatile(paravirt_alt(PARAVIRT_CALL)		\
 			     : call_clbr, ASM_CALL_CONSTRAINT		\
 			     : paravirt_type(op),			\
 			       paravirt_clobber(clbr),			\
 			       ##__VA_ARGS__				\
 			     : "memory", "cc" extra_clbr);		\
-		(rettype)(__eax & PVOP_RETMASK(rettype));		\
+		ret;							\
 	})
 
 #define __PVOP_CALL(rettype, op, ...)					\
-	____PVOP_CALL(rettype, op, CLBR_ANY, PVOP_CALL_CLOBBERS,	\
-		      EXTRA_CLOBBERS, ##__VA_ARGS__)
+	____PVOP_CALL(PVOP_RETVAL(rettype), op, CLBR_ANY,		\
+		      PVOP_CALL_CLOBBERS, EXTRA_CLOBBERS, ##__VA_ARGS__)
 
 #define __PVOP_CALLEESAVE(rettype, op, ...)				\
-	____PVOP_CALL(rettype, op.func, CLBR_RET_REG,			\
+	____PVOP_CALL(PVOP_RETVAL(rettype), op.func, CLBR_RET_REG,	\
 		      PVOP_CALLEE_CLOBBERS, , ##__VA_ARGS__)
 
-
-#define ____PVOP_VCALL(op, clbr, call_clbr, extra_clbr, ...)		\
-	({								\
-		PVOP_VCALL_ARGS;					\
-		PVOP_TEST_NULL(op);					\
-		asm volatile(paravirt_alt(PARAVIRT_CALL)		\
-			     : call_clbr, ASM_CALL_CONSTRAINT		\
-			     : paravirt_type(op),			\
-			       paravirt_clobber(clbr),			\
-			       ##__VA_ARGS__				\
-			     : "memory", "cc" extra_clbr);		\
-	})
-
 #define __PVOP_VCALL(op, ...)						\
-	____PVOP_VCALL(op, CLBR_ANY, PVOP_VCALL_CLOBBERS,		\
+	(void)____PVOP_CALL(, op, CLBR_ANY, PVOP_VCALL_CLOBBERS,	\
 		       VEXTRA_CLOBBERS, ##__VA_ARGS__)
 
 #define __PVOP_VCALLEESAVE(op, ...)					\
-	____PVOP_VCALL(op.func, CLBR_RET_REG,				\
+	(void)____PVOP_CALL(, op.func, CLBR_RET_REG,			\
 		      PVOP_VCALLEE_CLOBBERS, , ##__VA_ARGS__)
 
 
-- 
2.26.2

[PATCH v5 09/12] x86/paravirt: switch iret pvops to ALTERNATIVE

[Juergen Gross]

The iret paravirt op is rather special as it is using a jmp instead
of a call instruction. Switch it to ALTERNATIVE.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- use ALTERNATIVE_TERNARY
---
 arch/x86/include/asm/paravirt.h       |  6 +++---
 arch/x86/include/asm/paravirt_types.h |  5 +----
 arch/x86/kernel/asm-offsets.c         |  5 -----
 arch/x86/kernel/paravirt.c            | 26 ++------------------------
 arch/x86/xen/enlighten_pv.c           |  3 +--
 5 files changed, 7 insertions(+), 38 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index c6496a82fad1..36cd71fa097f 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -749,9 +749,9 @@ extern void default_banner(void);
 #define PARA_INDIRECT(addr)	*addr(%rip)
 
 #define INTERRUPT_RETURN						\
-	PARA_SITE(PARA_PATCH(PV_CPU_iret),				\
-		  ANNOTATE_RETPOLINE_SAFE;				\
-		  jmp PARA_INDIRECT(pv_ops+PV_CPU_iret);)
+	ANNOTATE_RETPOLINE_SAFE;					\
+	ALTERNATIVE_TERNARY("jmp *paravirt_iret(%rip);",		\
+		X86_FEATURE_XENPV, "jmp xen_iret;", "jmp native_iret;")
 
 #ifdef CONFIG_DEBUG_ENTRY
 #define SAVE_FLAGS(clobbers)                                        \
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 45bd21647dd8..0afdac83f926 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -151,10 +151,6 @@ struct pv_cpu_ops {
 
 	u64 (*read_pmc)(int counter);
 
-	/* Normal iret.  Jump to this with the standard iret stack
-	   frame set up. */
-	void (*iret)(void);
-
 	void (*start_context_switch)(struct task_struct *prev);
 	void (*end_context_switch)(struct task_struct *next);
 #endif
@@ -294,6 +290,7 @@ struct paravirt_patch_template {
 
 extern struct pv_info pv_info;
 extern struct paravirt_patch_template pv_ops;
+extern void (*paravirt_iret)(void);
 
 #define PARAVIRT_PATCH(x)					\
 	(offsetof(struct paravirt_patch_template, x) / sizeof(void *))
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 736508004b30..ecd3fd6993d1 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -61,11 +61,6 @@ static void __used common(void)
 	OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe_ia32, uc.uc_mcontext);
 #endif
 
-#ifdef CONFIG_PARAVIRT_XXL
-	BLANK();
-	OFFSET(PV_CPU_iret, paravirt_patch_template, cpu.iret);
-#endif
-
 #ifdef CONFIG_XEN
 	BLANK();
 	OFFSET(XEN_vcpu_info_mask, vcpu_info, evtchn_upcall_mask);
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 44e5b0fe28cb..0553a339d850 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -86,25 +86,6 @@ u64 notrace _paravirt_ident_64(u64 x)
 {
 	return x;
 }
-
-static unsigned paravirt_patch_jmp(void *insn_buff, const void *target,
-				   unsigned long addr, unsigned len)
-{
-	struct branch *b = insn_buff;
-	unsigned long delta = (unsigned long)target - (addr+5);
-
-	if (len < 5) {
-#ifdef CONFIG_RETPOLINE
-		WARN_ONCE(1, "Failing to patch indirect JMP in %ps\n", (void *)addr);
-#endif
-		return len;	/* call too long for patch site */
-	}
-
-	b->opcode = 0xe9;	/* jmp */
-	b->delta = delta;
-
-	return 5;
-}
 #endif
 
 DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
@@ -136,9 +117,6 @@ unsigned paravirt_patch_default(u8 type, void *insn_buff,
 	else if (opfunc == _paravirt_ident_64)
 		ret = paravirt_patch_ident_64(insn_buff, len);
 
-	else if (type == PARAVIRT_PATCH(cpu.iret))
-		/* If operation requires a jmp, then jmp */
-		ret = paravirt_patch_jmp(insn_buff, opfunc, addr, len);
 #endif
 	else
 		/* Otherwise call the function. */
@@ -316,8 +294,6 @@ struct paravirt_patch_template pv_ops = {
 
 	.cpu.load_sp0		= native_load_sp0,
 
-	.cpu.iret		= native_iret,
-
 #ifdef CONFIG_X86_IOPL_IOPERM
 	.cpu.invalidate_io_bitmap	= native_tss_invalidate_io_bitmap,
 	.cpu.update_io_bitmap		= native_tss_update_io_bitmap,
@@ -422,6 +398,8 @@ struct paravirt_patch_template pv_ops = {
 NOKPROBE_SYMBOL(native_get_debugreg);
 NOKPROBE_SYMBOL(native_set_debugreg);
 NOKPROBE_SYMBOL(native_load_idt);
+
+void (*paravirt_iret)(void) = native_iret;
 #endif
 
 EXPORT_SYMBOL(pv_ops);
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index dc0a337f985b..08dca7bebb30 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1070,8 +1070,6 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 
 	.read_pmc = xen_read_pmc,
 
-	.iret = xen_iret,
-
 	.load_tr_desc = paravirt_nop,
 	.set_ldt = xen_set_ldt,
 	.load_gdt = xen_load_gdt,
@@ -1235,6 +1233,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 	pv_info = xen_info;
 	pv_ops.init.patch = paravirt_patch_default;
 	pv_ops.cpu = xen_cpu_ops;
+	paravirt_iret = xen_iret;
 	xen_init_irq_ops();
 
 	/*
-- 
2.26.2

[PATCH v5 10/12] x86/paravirt: add new macros PVOP_ALT* supporting pvops in ALTERNATIVEs

[Juergen Gross]

Instead of using paravirt patching for custom code sequences add
support for using ALTERNATIVE handling combined with paravirt call
patching.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- drop ____PVOP_ALT_VCALL() macro
---
 arch/x86/include/asm/paravirt_types.h | 49 ++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 0afdac83f926..0ed976286d49 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -477,44 +477,91 @@ int paravirt_disable_iospace(void);
 		ret;							\
 	})
 
+#define ____PVOP_ALT_CALL(ret, op, alt, cond, clbr, call_clbr,		\
+			  extra_clbr, ...)				\
+	({								\
+		PVOP_CALL_ARGS;						\
+		PVOP_TEST_NULL(op);					\
+		asm volatile(ALTERNATIVE(paravirt_alt(PARAVIRT_CALL),	\
+					 alt, cond)			\
+			     : call_clbr, ASM_CALL_CONSTRAINT		\
+			     : paravirt_type(op),			\
+			       paravirt_clobber(clbr),			\
+			       ##__VA_ARGS__				\
+			     : "memory", "cc" extra_clbr);		\
+		ret;							\
+	})
+
 #define __PVOP_CALL(rettype, op, ...)					\
 	____PVOP_CALL(PVOP_RETVAL(rettype), op, CLBR_ANY,		\
 		      PVOP_CALL_CLOBBERS, EXTRA_CLOBBERS, ##__VA_ARGS__)
 
+#define __PVOP_ALT_CALL(rettype, op, alt, cond, ...)			\
+	____PVOP_ALT_CALL(PVOP_RETVAL(rettype), op, alt, cond, CLBR_ANY,\
+			  PVOP_CALL_CLOBBERS, EXTRA_CLOBBERS,		\
+			  ##__VA_ARGS__)
+
 #define __PVOP_CALLEESAVE(rettype, op, ...)				\
 	____PVOP_CALL(PVOP_RETVAL(rettype), op.func, CLBR_RET_REG,	\
 		      PVOP_CALLEE_CLOBBERS, , ##__VA_ARGS__)
 
+#define __PVOP_ALT_CALLEESAVE(rettype, op, alt, cond, ...)		\
+	____PVOP_ALT_CALL(PVOP_RETVAL(rettype), op.func, alt, cond,	\
+			  CLBR_RET_REG, PVOP_CALLEE_CLOBBERS, , ##__VA_ARGS__)
+
+
 #define __PVOP_VCALL(op, ...)						\
 	(void)____PVOP_CALL(, op, CLBR_ANY, PVOP_VCALL_CLOBBERS,	\
 		       VEXTRA_CLOBBERS, ##__VA_ARGS__)
 
+#define __PVOP_ALT_VCALL(op, alt, cond, ...)				\
+	(void)____PVOP_ALT_CALL(, op, alt, cond, CLBR_ANY,		\
+				PVOP_VCALL_CLOBBERS, VEXTRA_CLOBBERS,	\
+				##__VA_ARGS__)
+
 #define __PVOP_VCALLEESAVE(op, ...)					\
 	(void)____PVOP_CALL(, op.func, CLBR_RET_REG,			\
-		      PVOP_VCALLEE_CLOBBERS, , ##__VA_ARGS__)
+			    PVOP_VCALLEE_CLOBBERS, , ##__VA_ARGS__)
 
+#define __PVOP_ALT_VCALLEESAVE(op, alt, cond, ...)			\
+	(void)____PVOP_ALT_CALL(, op.func, alt, cond, CLBR_RET_REG,	\
+				PVOP_VCALLEE_CLOBBERS, , ##__VA_ARGS__)
 
 
 #define PVOP_CALL0(rettype, op)						\
 	__PVOP_CALL(rettype, op)
 #define PVOP_VCALL0(op)							\
 	__PVOP_VCALL(op)
+#define PVOP_ALT_CALL0(rettype, op, alt, cond)				\
+	__PVOP_ALT_CALL(rettype, op, alt, cond)
+#define PVOP_ALT_VCALL0(op, alt, cond)					\
+	__PVOP_ALT_VCALL(op, alt, cond)
 
 #define PVOP_CALLEE0(rettype, op)					\
 	__PVOP_CALLEESAVE(rettype, op)
 #define PVOP_VCALLEE0(op)						\
 	__PVOP_VCALLEESAVE(op)
+#define PVOP_ALT_CALLEE0(rettype, op, alt, cond)			\
+	__PVOP_ALT_CALLEESAVE(rettype, op, alt, cond)
+#define PVOP_ALT_VCALLEE0(op, alt, cond)				\
+	__PVOP_ALT_VCALLEESAVE(op, alt, cond)
 
 
 #define PVOP_CALL1(rettype, op, arg1)					\
 	__PVOP_CALL(rettype, op, PVOP_CALL_ARG1(arg1))
 #define PVOP_VCALL1(op, arg1)						\
 	__PVOP_VCALL(op, PVOP_CALL_ARG1(arg1))
+#define PVOP_ALT_VCALL1(op, arg1, alt, cond)				\
+	__PVOP_ALT_VCALL(op, alt, cond, PVOP_CALL_ARG1(arg1))
 
 #define PVOP_CALLEE1(rettype, op, arg1)					\
 	__PVOP_CALLEESAVE(rettype, op, PVOP_CALL_ARG1(arg1))
 #define PVOP_VCALLEE1(op, arg1)						\
 	__PVOP_VCALLEESAVE(op, PVOP_CALL_ARG1(arg1))
+#define PVOP_ALT_CALLEE1(rettype, op, arg1, alt, cond)			\
+	__PVOP_ALT_CALLEESAVE(rettype, op, alt, cond, PVOP_CALL_ARG1(arg1))
+#define PVOP_ALT_VCALLEE1(op, arg1, alt, cond)				\
+	__PVOP_ALT_VCALLEESAVE(op, alt, cond, PVOP_CALL_ARG1(arg1))
 
 
 #define PVOP_CALL2(rettype, op, arg1, arg2)				\
-- 
2.26.2

[PATCH v5 11/12] x86/paravirt: switch functions with custom code to ALTERNATIVE

[Juergen Gross]

Instead of using paravirt patching for custom code sequences use
ALTERNATIVE for the functions with custom code replacements.

Instead of patching an ud2 instruction for unpopulated vector entries
into the caller site, use a simple function just calling BUG() as a
replacement.

Simplify the register defines for assembler paravirt calling, as there
isn't much usage left.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V4:
- fixed SAVE_FLAGS() (kernel test robot)
- added assembler paravirt cleanup
---
 arch/x86/entry/entry_64.S             |  2 +-
 arch/x86/include/asm/irqflags.h       |  2 +-
 arch/x86/include/asm/paravirt.h       | 99 +++++++++++++--------------
 arch/x86/include/asm/paravirt_types.h |  6 --
 arch/x86/kernel/paravirt.c            | 16 ++---
 arch/x86/kernel/paravirt_patch.c      | 88 ------------------------
 6 files changed, 56 insertions(+), 157 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 400908dff42e..12e2e3cd58be 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -305,7 +305,7 @@ SYM_CODE_END(ret_from_fork)
 .macro DEBUG_ENTRY_ASSERT_IRQS_OFF
 #ifdef CONFIG_DEBUG_ENTRY
 	pushq %rax
-	SAVE_FLAGS(CLBR_RAX)
+	SAVE_FLAGS
 	testl $X86_EFLAGS_IF, %eax
 	jz .Lokay_\@
 	ud2
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index a0efbcd24b86..c5ce9845c999 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -111,7 +111,7 @@ static __always_inline unsigned long arch_local_irq_save(void)
 
 #ifdef CONFIG_X86_64
 #ifdef CONFIG_DEBUG_ENTRY
-#define SAVE_FLAGS(x)		pushfq; popq %rax
+#define SAVE_FLAGS		pushfq; popq %rax
 #endif
 
 #define INTERRUPT_RETURN	jmp native_iret
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 36cd71fa097f..04b3067f31b5 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -137,7 +137,8 @@ static inline void write_cr0(unsigned long x)
 
 static inline unsigned long read_cr2(void)
 {
-	return PVOP_CALLEE0(unsigned long, mmu.read_cr2);
+	return PVOP_ALT_CALLEE0(unsigned long, mmu.read_cr2,
+				"mov %%cr2, %%rax;", ~X86_FEATURE_XENPV);
 }
 
 static inline void write_cr2(unsigned long x)
@@ -147,12 +148,14 @@ static inline void write_cr2(unsigned long x)
 
 static inline unsigned long __read_cr3(void)
 {
-	return PVOP_CALL0(unsigned long, mmu.read_cr3);
+	return PVOP_ALT_CALL0(unsigned long, mmu.read_cr3,
+			      "mov %%cr3, %%rax;", ~X86_FEATURE_XENPV);
 }
 
 static inline void write_cr3(unsigned long x)
 {
-	PVOP_VCALL1(mmu.write_cr3, x);
+	PVOP_ALT_VCALL1(mmu.write_cr3, x,
+			"mov %%rdi, %%cr3", ~X86_FEATURE_XENPV);
 }
 
 static inline void __write_cr4(unsigned long x)
@@ -172,7 +175,7 @@ static inline void halt(void)
 
 static inline void wbinvd(void)
 {
-	PVOP_VCALL0(cpu.wbinvd);
+	PVOP_ALT_VCALL0(cpu.wbinvd, "wbinvd", ~X86_FEATURE_XENPV);
 }
 
 static inline u64 paravirt_read_msr(unsigned msr)
@@ -386,22 +389,28 @@ static inline void paravirt_release_p4d(unsigned long pfn)
 
 static inline pte_t __pte(pteval_t val)
 {
-	return (pte_t) { PVOP_CALLEE1(pteval_t, mmu.make_pte, val) };
+	return (pte_t) { PVOP_ALT_CALLEE1(pteval_t, mmu.make_pte, val,
+					  "mov %%rdi, %%rax",
+					  ~X86_FEATURE_XENPV) };
 }
 
 static inline pteval_t pte_val(pte_t pte)
 {
-	return PVOP_CALLEE1(pteval_t, mmu.pte_val, pte.pte);
+	return PVOP_ALT_CALLEE1(pteval_t, mmu.pte_val, pte.pte,
+				"mov %%rdi, %%rax", ~X86_FEATURE_XENPV);
 }
 
 static inline pgd_t __pgd(pgdval_t val)
 {
-	return (pgd_t) { PVOP_CALLEE1(pgdval_t, mmu.make_pgd, val) };
+	return (pgd_t) { PVOP_ALT_CALLEE1(pgdval_t, mmu.make_pgd, val,
+					  "mov %%rdi, %%rax",
+					  ~X86_FEATURE_XENPV) };
 }
 
 static inline pgdval_t pgd_val(pgd_t pgd)
 {
-	return PVOP_CALLEE1(pgdval_t, mmu.pgd_val, pgd.pgd);
+	return PVOP_ALT_CALLEE1(pgdval_t, mmu.pgd_val, pgd.pgd,
+				"mov %%rdi, %%rax", ~X86_FEATURE_XENPV);
 }
 
 #define  __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
@@ -434,12 +443,15 @@ static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
 
 static inline pmd_t __pmd(pmdval_t val)
 {
-	return (pmd_t) { PVOP_CALLEE1(pmdval_t, mmu.make_pmd, val) };
+	return (pmd_t) { PVOP_ALT_CALLEE1(pmdval_t, mmu.make_pmd, val,
+					  "mov %%rdi, %%rax",
+					  ~X86_FEATURE_XENPV) };
 }
 
 static inline pmdval_t pmd_val(pmd_t pmd)
 {
-	return PVOP_CALLEE1(pmdval_t, mmu.pmd_val, pmd.pmd);
+	return PVOP_ALT_CALLEE1(pmdval_t, mmu.pmd_val, pmd.pmd,
+				"mov %%rdi, %%rax", ~X86_FEATURE_XENPV);
 }
 
 static inline void set_pud(pud_t *pudp, pud_t pud)
@@ -451,14 +463,16 @@ static inline pud_t __pud(pudval_t val)
 {
 	pudval_t ret;
 
-	ret = PVOP_CALLEE1(pudval_t, mmu.make_pud, val);
+	ret = PVOP_ALT_CALLEE1(pudval_t, mmu.make_pud, val,
+			       "mov %%rdi, %%rax", ~X86_FEATURE_XENPV);
 
 	return (pud_t) { ret };
 }
 
 static inline pudval_t pud_val(pud_t pud)
 {
-	return PVOP_CALLEE1(pudval_t, mmu.pud_val, pud.pud);
+	return PVOP_ALT_CALLEE1(pudval_t, mmu.pud_val, pud.pud,
+				"mov %%rdi, %%rax", ~X86_FEATURE_XENPV);
 }
 
 static inline void pud_clear(pud_t *pudp)
@@ -477,14 +491,16 @@ static inline void set_p4d(p4d_t *p4dp, p4d_t p4d)
 
 static inline p4d_t __p4d(p4dval_t val)
 {
-	p4dval_t ret = PVOP_CALLEE1(p4dval_t, mmu.make_p4d, val);
+	p4dval_t ret = PVOP_ALT_CALLEE1(p4dval_t, mmu.make_p4d, val,
+					"mov %%rdi, %%rax", ~X86_FEATURE_XENPV);
 
 	return (p4d_t) { ret };
 }
 
 static inline p4dval_t p4d_val(p4d_t p4d)
 {
-	return PVOP_CALLEE1(p4dval_t, mmu.p4d_val, p4d.p4d);
+	return PVOP_ALT_CALLEE1(p4dval_t, mmu.p4d_val, p4d.p4d,
+				"mov %%rdi, %%rax", ~X86_FEATURE_XENPV);
 }
 
 static inline void __set_pgd(pgd_t *pgdp, pgd_t pgd)
@@ -571,7 +587,9 @@ static __always_inline void pv_queued_spin_lock_slowpath(struct qspinlock *lock,
 
 static __always_inline void pv_queued_spin_unlock(struct qspinlock *lock)
 {
-	PVOP_VCALLEE1(lock.queued_spin_unlock, lock);
+	PVOP_ALT_VCALLEE1(lock.queued_spin_unlock, lock,
+			  "movb $0, (%%" _ASM_ARG1 ");",
+			  ~X86_FEATURE_PVUNLOCK);
 }
 
 static __always_inline void pv_wait(u8 *ptr, u8 val)
@@ -586,7 +604,9 @@ static __always_inline void pv_kick(int cpu)
 
 static __always_inline bool pv_vcpu_is_preempted(long cpu)
 {
-	return PVOP_CALLEE1(bool, lock.vcpu_is_preempted, cpu);
+	return PVOP_ALT_CALLEE1(bool, lock.vcpu_is_preempted, cpu,
+				"xor %%" _ASM_AX ", %%" _ASM_AX ";",
+				~X86_FEATURE_VCPUPREEMPT);
 }
 
 void __raw_callee_save___native_queued_spin_unlock(struct qspinlock *lock);
@@ -660,17 +680,18 @@ bool __raw_callee_save___native_vcpu_is_preempted(long cpu);
 #ifdef CONFIG_PARAVIRT_XXL
 static inline notrace unsigned long arch_local_save_flags(void)
 {
-	return PVOP_CALLEE0(unsigned long, irq.save_fl);
+	return PVOP_ALT_CALLEE0(unsigned long, irq.save_fl,
+				"pushf; pop %%rax;", ~X86_FEATURE_XENPV);
 }
 
 static inline notrace void arch_local_irq_disable(void)
 {
-	PVOP_VCALLEE0(irq.irq_disable);
+	PVOP_ALT_VCALLEE0(irq.irq_disable, "cli;", ~X86_FEATURE_XENPV);
 }
 
 static inline notrace void arch_local_irq_enable(void)
 {
-	PVOP_VCALLEE0(irq.irq_enable);
+	PVOP_ALT_VCALLEE0(irq.irq_enable, "sti;", ~X86_FEATURE_XENPV);
 }
 
 static inline notrace unsigned long arch_local_irq_save(void)
@@ -715,35 +736,9 @@ extern void default_banner(void);
 	.popsection
 
 
-#define COND_PUSH(set, mask, reg)			\
-	.if ((~(set)) & mask); push %reg; .endif
-#define COND_POP(set, mask, reg)			\
-	.if ((~(set)) & mask); pop %reg; .endif
-
 #ifdef CONFIG_X86_64
 #ifdef CONFIG_PARAVIRT_XXL
 
-#define PV_SAVE_REGS(set)			\
-	COND_PUSH(set, CLBR_RAX, rax);		\
-	COND_PUSH(set, CLBR_RCX, rcx);		\
-	COND_PUSH(set, CLBR_RDX, rdx);		\
-	COND_PUSH(set, CLBR_RSI, rsi);		\
-	COND_PUSH(set, CLBR_RDI, rdi);		\
-	COND_PUSH(set, CLBR_R8, r8);		\
-	COND_PUSH(set, CLBR_R9, r9);		\
-	COND_PUSH(set, CLBR_R10, r10);		\
-	COND_PUSH(set, CLBR_R11, r11)
-#define PV_RESTORE_REGS(set)			\
-	COND_POP(set, CLBR_R11, r11);		\
-	COND_POP(set, CLBR_R10, r10);		\
-	COND_POP(set, CLBR_R9, r9);		\
-	COND_POP(set, CLBR_R8, r8);		\
-	COND_POP(set, CLBR_RDI, rdi);		\
-	COND_POP(set, CLBR_RSI, rsi);		\
-	COND_POP(set, CLBR_RDX, rdx);		\
-	COND_POP(set, CLBR_RCX, rcx);		\
-	COND_POP(set, CLBR_RAX, rax)
-
 #define PARA_PATCH(off)		((off) / 8)
 #define PARA_SITE(ptype, ops)	_PVSITE(ptype, ops, .quad, 8)
 #define PARA_INDIRECT(addr)	*addr(%rip)
@@ -754,12 +749,14 @@ extern void default_banner(void);
 		X86_FEATURE_XENPV, "jmp xen_iret;", "jmp native_iret;")
 
 #ifdef CONFIG_DEBUG_ENTRY
-#define SAVE_FLAGS(clobbers)                                        \
-	PARA_SITE(PARA_PATCH(PV_IRQ_save_fl),			    \
-		  PV_SAVE_REGS(clobbers | CLBR_CALLEE_SAVE);        \
-		  ANNOTATE_RETPOLINE_SAFE;			    \
-		  call PARA_INDIRECT(pv_ops+PV_IRQ_save_fl);	    \
-		  PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);)
+.macro PARA_IRQ_save_fl
+	PARA_SITE(PARA_PATCH(PV_IRQ_save_fl),
+		  ANNOTATE_RETPOLINE_SAFE;
+		  call PARA_INDIRECT(pv_ops+PV_IRQ_save_fl);)
+.endm
+
+#define SAVE_FLAGS	ALTERNATIVE "PARA_IRQ_save_fl;", "pushf; pop %rax;", \
+				    ~X86_FEATURE_XENPV
 #endif
 #endif /* CONFIG_PARAVIRT_XXL */
 #endif	/* CONFIG_X86_64 */
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 0ed976286d49..588ff14ce969 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -3,7 +3,6 @@
 #define _ASM_X86_PARAVIRT_TYPES_H
 
 /* Bitmask of what can be clobbered: usually at least eax. */
-#define CLBR_NONE 0
 #define CLBR_EAX  (1 << 0)
 #define CLBR_ECX  (1 << 1)
 #define CLBR_EDX  (1 << 2)
@@ -15,7 +14,6 @@
 
 #define CLBR_ARG_REGS	(CLBR_EAX | CLBR_EDX | CLBR_ECX)
 #define CLBR_RET_REG	(CLBR_EAX | CLBR_EDX)
-#define CLBR_SCRATCH	(0)
 #else
 #define CLBR_RAX  CLBR_EAX
 #define CLBR_RCX  CLBR_ECX
@@ -32,12 +30,9 @@
 #define CLBR_ARG_REGS	(CLBR_RDI | CLBR_RSI | CLBR_RDX | \
 			 CLBR_RCX | CLBR_R8 | CLBR_R9)
 #define CLBR_RET_REG	(CLBR_RAX)
-#define CLBR_SCRATCH	(CLBR_R10 | CLBR_R11)
 
 #endif /* X86_64 */
 
-#define CLBR_CALLEE_SAVE ((CLBR_ARG_REGS | CLBR_SCRATCH) & ~CLBR_RET_REG)
-
 #ifndef __ASSEMBLY__
 
 #include <asm/desc_defs.h>
@@ -322,7 +317,6 @@ extern void (*paravirt_iret)(void);
 /* Simple instruction patching code. */
 #define NATIVE_LABEL(a,x,b) "\n\t.globl " a #x "_" #b "\n" a #x "_" #b ":\n\t"
 
-unsigned paravirt_patch_ident_64(void *insn_buff, unsigned len);
 unsigned paravirt_patch_default(u8 type, void *insn_buff, unsigned long addr, unsigned len);
 unsigned paravirt_patch_insns(void *insn_buff, unsigned len, const char *start, const char *end);
 
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 0553a339d850..082954930809 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -53,7 +53,10 @@ void __init default_banner(void)
 }
 
 /* Undefined instruction for dealing with missing ops pointers. */
-static const unsigned char ud2a[] = { 0x0f, 0x0b };
+static void paravirt_BUG(void)
+{
+	BUG();
+}
 
 struct branch {
 	unsigned char opcode;
@@ -107,17 +110,10 @@ unsigned paravirt_patch_default(u8 type, void *insn_buff,
 	unsigned ret;
 
 	if (opfunc == NULL)
-		/* If there's no function, patch it with a ud2a (BUG) */
-		ret = paravirt_patch_insns(insn_buff, len, ud2a, ud2a+sizeof(ud2a));
+		/* If there's no function, patch it with paravirt_BUG() */
+		ret = paravirt_patch_call(insn_buff, paravirt_BUG, addr, len);
 	else if (opfunc == _paravirt_nop)
 		ret = 0;
-
-#ifdef CONFIG_PARAVIRT_XXL
-	/* identity functions just return their single argument */
-	else if (opfunc == _paravirt_ident_64)
-		ret = paravirt_patch_ident_64(insn_buff, len);
-
-#endif
 	else
 		/* Otherwise call the function. */
 		ret = paravirt_patch_call(insn_buff, opfunc, addr, len);
diff --git a/arch/x86/kernel/paravirt_patch.c b/arch/x86/kernel/paravirt_patch.c
index abd27ec67397..10543dcc8211 100644
--- a/arch/x86/kernel/paravirt_patch.c
+++ b/arch/x86/kernel/paravirt_patch.c
@@ -4,96 +4,8 @@
 #include <asm/paravirt.h>
 #include <asm/asm-offsets.h>
 
-#define PSTART(d, m)							\
-	patch_data_##d.m
-
-#define PEND(d, m)							\
-	(PSTART(d, m) + sizeof(patch_data_##d.m))
-
-#define PATCH(d, m, insn_buff, len)						\
-	paravirt_patch_insns(insn_buff, len, PSTART(d, m), PEND(d, m))
-
-#define PATCH_CASE(ops, m, data, insn_buff, len)				\
-	case PARAVIRT_PATCH(ops.m):					\
-		return PATCH(data, ops##_##m, insn_buff, len)
-
-#ifdef CONFIG_PARAVIRT_XXL
-struct patch_xxl {
-	const unsigned char	irq_irq_disable[1];
-	const unsigned char	irq_irq_enable[1];
-	const unsigned char	irq_save_fl[2];
-	const unsigned char	mmu_read_cr2[3];
-	const unsigned char	mmu_read_cr3[3];
-	const unsigned char	mmu_write_cr3[3];
-	const unsigned char	cpu_wbinvd[2];
-	const unsigned char	mov64[3];
-};
-
-static const struct patch_xxl patch_data_xxl = {
-	.irq_irq_disable	= { 0xfa },		// cli
-	.irq_irq_enable		= { 0xfb },		// sti
-	.irq_save_fl		= { 0x9c, 0x58 },	// pushf; pop %[re]ax
-	.mmu_read_cr2		= { 0x0f, 0x20, 0xd0 },	// mov %cr2, %[re]ax
-	.mmu_read_cr3		= { 0x0f, 0x20, 0xd8 },	// mov %cr3, %[re]ax
-	.mmu_write_cr3		= { 0x0f, 0x22, 0xdf },	// mov %rdi, %cr3
-	.cpu_wbinvd		= { 0x0f, 0x09 },	// wbinvd
-	.mov64			= { 0x48, 0x89, 0xf8 },	// mov %rdi, %rax
-};
-
-unsigned int paravirt_patch_ident_64(void *insn_buff, unsigned int len)
-{
-	return PATCH(xxl, mov64, insn_buff, len);
-}
-# endif /* CONFIG_PARAVIRT_XXL */
-
-#ifdef CONFIG_PARAVIRT_SPINLOCKS
-struct patch_lock {
-	unsigned char queued_spin_unlock[3];
-	unsigned char vcpu_is_preempted[2];
-};
-
-static const struct patch_lock patch_data_lock = {
-	.vcpu_is_preempted	= { 0x31, 0xc0 },	// xor %eax, %eax
-
-# ifdef CONFIG_X86_64
-	.queued_spin_unlock	= { 0xc6, 0x07, 0x00 },	// movb $0, (%rdi)
-# else
-	.queued_spin_unlock	= { 0xc6, 0x00, 0x00 },	// movb $0, (%eax)
-# endif
-};
-#endif /* CONFIG_PARAVIRT_SPINLOCKS */
-
 unsigned int native_patch(u8 type, void *insn_buff, unsigned long addr,
 			  unsigned int len)
 {
-	switch (type) {
-
-#ifdef CONFIG_PARAVIRT_XXL
-	PATCH_CASE(irq, save_fl, xxl, insn_buff, len);
-	PATCH_CASE(irq, irq_enable, xxl, insn_buff, len);
-	PATCH_CASE(irq, irq_disable, xxl, insn_buff, len);
-
-	PATCH_CASE(mmu, read_cr2, xxl, insn_buff, len);
-	PATCH_CASE(mmu, read_cr3, xxl, insn_buff, len);
-	PATCH_CASE(mmu, write_cr3, xxl, insn_buff, len);
-
-	PATCH_CASE(cpu, wbinvd, xxl, insn_buff, len);
-#endif
-
-#ifdef CONFIG_PARAVIRT_SPINLOCKS
-	case PARAVIRT_PATCH(lock.queued_spin_unlock):
-		if (pv_is_native_spin_unlock())
-			return PATCH(lock, queued_spin_unlock, insn_buff, len);
-		break;
-
-	case PARAVIRT_PATCH(lock.vcpu_is_preempted):
-		if (pv_is_native_vcpu_is_preempted())
-			return PATCH(lock, vcpu_is_preempted, insn_buff, len);
-		break;
-#endif
-	default:
-		break;
-	}
-
 	return paravirt_patch_default(type, insn_buff, addr, len);
 }
-- 
2.26.2

Re: [PATCH v5 11/12] x86/paravirt: switch functions with custom code to ALTERNATIVE

[Borislav Petkov]

On Mon, Mar 08, 2021 at 01:28:43PM +0100, Juergen Gross wrote:
> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
> index 36cd71fa097f..04b3067f31b5 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -137,7 +137,8 @@ static inline void write_cr0(unsigned long x)
>  
>  static inline unsigned long read_cr2(void)
>  {
> -	return PVOP_CALLEE0(unsigned long, mmu.read_cr2);
> +	return PVOP_ALT_CALLEE0(unsigned long, mmu.read_cr2,
> +				"mov %%cr2, %%rax;", ~X86_FEATURE_XENPV);

Just some cursory poking first - indepth review later.

Do I see this correctly that the negated feature can be expressed with, to use
this example here:

	ALTERNATIVE_TERNARY(mmu.read_cr2, X86_FEATURE_XENPV, "", "mov %%cr2, %%rax;");

?

And then you don't need to touch the patching code for ~feature handling
and the flags byte.

If you want it syntactically sugared, you can define a separate
ALTERNATIVE_NOT macro using ALTERNATIVE_TERNARY...

Hmmm.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v5 11/12] x86/paravirt: switch functions with custom code to ALTERNATIVE

[Jürgen Groß]

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On 08.03.21 19:30, Borislav Petkov wrote:
> On Mon, Mar 08, 2021 at 01:28:43PM +0100, Juergen Gross wrote:
>> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
>> index 36cd71fa097f..04b3067f31b5 100644
>> --- a/arch/x86/include/asm/paravirt.h
>> +++ b/arch/x86/include/asm/paravirt.h
>> @@ -137,7 +137,8 @@ static inline void write_cr0(unsigned long x)
>>   
>>   static inline unsigned long read_cr2(void)
>>   {
>> -	return PVOP_CALLEE0(unsigned long, mmu.read_cr2);
>> +	return PVOP_ALT_CALLEE0(unsigned long, mmu.read_cr2,
>> +				"mov %%cr2, %%rax;", ~X86_FEATURE_XENPV);
> 
> Just some cursory poking first - indepth review later.
> 
> Do I see this correctly that the negated feature can be expressed with, to use
> this example here:
> 
> 	ALTERNATIVE_TERNARY(mmu.read_cr2, X86_FEATURE_XENPV, "", "mov %%cr2, %%rax;");
> 
> ?

No.

This would leave the Xen-pv case with a nop, while we need it to call
mmu.read_cr2().

In the Xen-pv case there must be _no_ alternative patching in order to
have the paravirt patching do its patching (indirect->direct call).

This is exactly the reason why I need to "not feature".

The only other solution I can think of would be a "split static_call"
handling using ALTERNATIVE_TERNARY():

ALTERNATIVE_TERNARY(initial_static_call(mmu.read_cr2),
                     X86_FEATURE_XENPV,
                     final_static_call(mmu.read_cr2),
                     "mov %%cr2, %%rax;");

with initial_static_call() doing an indirect call, while
final_static_call() would do a direct call.

Not sure we really want that.


Juergen

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[PATCH v5 12/12] x86/paravirt: have only one paravirt patch function

[Juergen Gross]

There is no need any longer to have different paravirt patch functions
for native and Xen. Eliminate native_patch() and rename
paravirt_patch_default() to paravirt_patch().

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- remove paravirt_patch_insns() (kernel test robot)
---
 arch/x86/include/asm/paravirt_types.h | 19 +------------------
 arch/x86/kernel/Makefile              |  3 +--
 arch/x86/kernel/alternative.c         |  2 +-
 arch/x86/kernel/paravirt.c            | 20 ++------------------
 arch/x86/kernel/paravirt_patch.c      | 11 -----------
 arch/x86/xen/enlighten_pv.c           |  1 -
 6 files changed, 5 insertions(+), 51 deletions(-)
 delete mode 100644 arch/x86/kernel/paravirt_patch.c

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 588ff14ce969..62efbf8bd8f0 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -68,19 +68,6 @@ struct pv_info {
 	const char *name;
 };
 
-struct pv_init_ops {
-	/*
-	 * Patch may replace one of the defined code sequences with
-	 * arbitrary code, subject to the same register constraints.
-	 * This generally means the code is not free to clobber any
-	 * registers other than EAX.  The patch function should return
-	 * the number of bytes of code generated, as we nop pad the
-	 * rest in generic code.
-	 */
-	unsigned (*patch)(u8 type, void *insn_buff,
-			  unsigned long addr, unsigned len);
-} __no_randomize_layout;
-
 #ifdef CONFIG_PARAVIRT_XXL
 struct pv_lazy_ops {
 	/* Set deferred update mode, used for batching operations. */
@@ -276,7 +263,6 @@ struct pv_lock_ops {
  * number for each function using the offset which we use to indicate
  * what to patch. */
 struct paravirt_patch_template {
-	struct pv_init_ops	init;
 	struct pv_cpu_ops	cpu;
 	struct pv_irq_ops	irq;
 	struct pv_mmu_ops	mmu;
@@ -317,10 +303,7 @@ extern void (*paravirt_iret)(void);
 /* Simple instruction patching code. */
 #define NATIVE_LABEL(a,x,b) "\n\t.globl " a #x "_" #b "\n" a #x "_" #b ":\n\t"
 
-unsigned paravirt_patch_default(u8 type, void *insn_buff, unsigned long addr, unsigned len);
-unsigned paravirt_patch_insns(void *insn_buff, unsigned len, const char *start, const char *end);
-
-unsigned native_patch(u8 type, void *insn_buff, unsigned long addr, unsigned len);
+unsigned int paravirt_patch(u8 type, void *insn_buff, unsigned long addr, unsigned int len);
 
 int paravirt_disable_iospace(void);
 
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 2ddf08351f0b..0704c2a94272 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -35,7 +35,6 @@ KASAN_SANITIZE_sev-es.o					:= n
 KCSAN_SANITIZE := n
 
 OBJECT_FILES_NON_STANDARD_test_nx.o			:= y
-OBJECT_FILES_NON_STANDARD_paravirt_patch.o		:= y
 
 ifdef CONFIG_FRAME_POINTER
 OBJECT_FILES_NON_STANDARD_ftrace_$(BITS).o		:= y
@@ -121,7 +120,7 @@ obj-$(CONFIG_AMD_NB)		+= amd_nb.o
 obj-$(CONFIG_DEBUG_NMI_SELFTEST) += nmi_selftest.o
 
 obj-$(CONFIG_KVM_GUEST)		+= kvm.o kvmclock.o
-obj-$(CONFIG_PARAVIRT)		+= paravirt.o paravirt_patch.o
+obj-$(CONFIG_PARAVIRT)		+= paravirt.o
 obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= paravirt-spinlocks.o
 obj-$(CONFIG_PARAVIRT_CLOCK)	+= pvclock.o
 obj-$(CONFIG_X86_PMEM_LEGACY_DEVICE) += pmem.o
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index ab9ad729fc5a..8f922b65c3c5 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -607,7 +607,7 @@ void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
 		BUG_ON(p->len > MAX_PATCH_LEN);
 		/* prep the buffer with the original instructions */
 		memcpy(insn_buff, p->instr, p->len);
-		used = pv_ops.init.patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
+		used = paravirt_patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
 
 		BUG_ON(used > p->len);
 
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 082954930809..3d7b989ed6be 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -99,8 +99,8 @@ void __init native_pv_lock_init(void)
 		static_branch_disable(&virt_spin_lock_key);
 }
 
-unsigned paravirt_patch_default(u8 type, void *insn_buff,
-				unsigned long addr, unsigned len)
+unsigned int paravirt_patch(u8 type, void *insn_buff, unsigned long addr,
+			    unsigned int len)
 {
 	/*
 	 * Neat trick to map patch type back to the call within the
@@ -121,19 +121,6 @@ unsigned paravirt_patch_default(u8 type, void *insn_buff,
 	return ret;
 }
 
-unsigned paravirt_patch_insns(void *insn_buff, unsigned len,
-			      const char *start, const char *end)
-{
-	unsigned insn_len = end - start;
-
-	/* Alternative instruction is too large for the patch site and we cannot continue: */
-	BUG_ON(insn_len > len || start == NULL);
-
-	memcpy(insn_buff, start, insn_len);
-
-	return insn_len;
-}
-
 struct static_key paravirt_steal_enabled;
 struct static_key paravirt_steal_rq_enabled;
 
@@ -255,9 +242,6 @@ struct pv_info pv_info = {
 #define PTE_IDENT	__PV_IS_CALLEE_SAVE(_paravirt_ident_64)
 
 struct paravirt_patch_template pv_ops = {
-	/* Init ops. */
-	.init.patch		= native_patch,
-
 	/* Cpu ops. */
 	.cpu.io_delay		= native_io_delay,
 
diff --git a/arch/x86/kernel/paravirt_patch.c b/arch/x86/kernel/paravirt_patch.c
deleted file mode 100644
index 10543dcc8211..000000000000
--- a/arch/x86/kernel/paravirt_patch.c
+++ /dev/null
@@ -1,11 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#include <linux/stringify.h>
-
-#include <asm/paravirt.h>
-#include <asm/asm-offsets.h>
-
-unsigned int native_patch(u8 type, void *insn_buff, unsigned long addr,
-			  unsigned int len)
-{
-	return paravirt_patch_default(type, insn_buff, addr, len);
-}
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 08dca7bebb30..4f18cd9eacd8 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1231,7 +1231,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
 	/* Install Xen paravirt ops */
 	pv_info = xen_info;
-	pv_ops.init.patch = paravirt_patch_default;
 	pv_ops.cpu = xen_cpu_ops;
 	paravirt_iret = xen_iret;
 	xen_init_irq_ops();
-- 
2.26.2

Re: [PATCH v5 00/12] x86: major paravirt cleanup

[Peter Zijlstra]

On Mon, Mar 08, 2021 at 01:28:32PM +0100, Juergen Gross wrote:
> This is a major cleanup of the paravirt infrastructure aiming at
> eliminating all custom code patching via paravirt patching.
> 
> This is achieved by using ALTERNATIVE instead, leading to the ability
> to give objtool access to the patched in instructions.
> 
> In order to remove most of the 32-bit special handling from pvops the
> time related operations are switched to use static_call() instead.
> 
> At the end of this series all paravirt patching has to do is to
> replace indirect calls with direct ones. In a further step this could
> be switched to static_call(), too.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

I've rebased my objtool/retpoline branch on top of this, will post
if/when this hits tip. Negative alternative works like a charm.