x86/rtc: Replace paravirt rtc check with platform legacy quirk

We have 4 types of x86 platforms that disable RTC:

  * Intel MID
  * Lguest - uses paravirt
  * Xen dom-U - uses paravirt
  * x86 on legacy systems annotated with an ACPI legacy flag

We can consolidate all of these into a platform specific legacy
quirk set early in boot through i386_start_kernel() and through
x86_64_start_reservations(). This deals with the RTC quirks which
we can rely on through the hardware subarch, the ACPI check can
be dealt with separately.

For Xen things are bit more complex given that the @X86_SUBARCH_XEN
x86_hardware_subarch is shared on for Xen which uses the PV path for
both domU and dom0. Since the semantics for differentiating between
the two are Xen specific we provide a platform helper to help override
default legacy features -- x86_platform.set_legacy_features(). Use
of this helper is highly discouraged, its only purpose should be
to account for the lack of semantics available within your given
x86_hardware_subarch.

As per 0-day, this bumps the vmlinux size using i386-tinyconfig as
follows:

TOTAL   TEXT   init.text    x86_early_init_platform_quirks()
+70     +62    +62          +43

Only 8 bytes overhead total, as the main increase in size is
all removed via __init.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: andrew.cooper3@citrix.com
Cc: andriy.shevchenko@linux.intel.com
Cc: bigeasy@linutronix.de
Cc: boris.ostrovsky@oracle.com
Cc: david.vrabel@citrix.com
Cc: ffainelli@freebox.fr
Cc: george.dunlap@citrix.com
Cc: glin@suse.com
Cc: jlee@suse.com
Cc: josh@joshtriplett.org
Cc: julien.grall@linaro.org
Cc: konrad.wilk@oracle.com
Cc: kozerkov@parallels.com
Cc: lenb@kernel.org
Cc: lguest@lists.ozlabs.org
Cc: linux-acpi@vger.kernel.org
Cc: lv.zheng@intel.com
Cc: matt@codeblueprint.co.uk
Cc: mbizon@freebox.fr
Cc: rjw@rjwysocki.net
Cc: robert.moore@intel.com
Cc: rusty@rustcorp.com.au
Cc: tiwai@suse.de
Cc: toshi.kani@hp.com
Cc: xen-devel@lists.xensource.com
Link: http://lkml.kernel.org/r/1460592286-300-5-git-send-email-mcgrof@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 4086abca0b32345c92207fa75468cc98ebe97da4..f9ed8a7ce2b61b85a70d4274b83ff4a0f9050237 100644 (file)
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -209,6 +209,7 @@ endif
 head-y := arch/x86/kernel/head_$(BITS).o
 head-y += arch/x86/kernel/head$(BITS).o
 head-y += arch/x86/kernel/head.o
+head-y += arch/x86/kernel/platform-quirks.o
 
 libs-y  += arch/x86/lib/
 

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 601f1b8f9961af35f113ad456b1ab90f1aceaced..6c7a4a192032865d29d1c7d50b2882f2a38bde3d 100644 (file)
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -20,12 +20,6 @@ static inline int paravirt_enabled(void)
        return pv_info.paravirt_enabled;
 }
 
-static inline int paravirt_has_feature(unsigned int feature)
-{
-       WARN_ON_ONCE(!pv_info.paravirt_enabled);
-       return (pv_info.features & feature);
-}
-
 static inline void load_sp0(struct tss_struct *tss,
                             struct thread_struct *thread)
 {

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index e8c2326478c8fabc4e03c04534c599072e2598fe..6acc1b26cf40add7650e6eb5fc2a1de61599ef10 100644 (file)
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -70,14 +70,9 @@ struct pv_info {
 #endif
 
        int paravirt_enabled;
-       unsigned int features;    /* valid only if paravirt_enabled is set */
        const char *name;
 };
 
-#define paravirt_has(x) paravirt_has_feature(PV_SUPPORTED_##x)
-/* Supported features */
-#define PV_SUPPORTED_RTC        (1<<0)
-
 struct pv_init_ops {
        /*
         * Patch may replace one of the defined code sequences with

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 9264476f3d578e8fa346411aad4900e85afcb41a..0c70c7daa6b83562ea46b266d2e409068e958ae3 100644 (file)
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -474,7 +474,6 @@ static inline unsigned long current_top_of_stack(void)
 #else
 #define __cpuid                        native_cpuid
 #define paravirt_enabled()     0
-#define paravirt_has(x)        0
 
 static inline void load_sp0(struct tss_struct *tss,
                            struct thread_struct *thread)

diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 1ae89a2721d6f5a120650630d317913c3ee2c32a..8bb8c1a4615a45aef388c2b5548f6efb725ff076 100644 (file)
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -141,6 +141,15 @@ struct x86_cpuinit_ops {
 
 struct timespec;
 
+/**
+ * struct x86_legacy_features - legacy x86 features
+ *
+ * @rtc: this device has a CMOS real-time clock present
+ */
+struct x86_legacy_features {
+       int rtc;
+};
+
 /**
  * struct x86_platform_ops - platform specific runtime functions
  * @calibrate_tsc:             calibrate TSC
@@ -152,6 +161,14 @@ struct timespec;
  * @save_sched_clock_state:    save state for sched_clock() on suspend
  * @restore_sched_clock_state: restore state for sched_clock() on resume
  * @apic_post_init:            adjust apic if neeeded
+ * @legacy:                    legacy features
+ * @set_legacy_features:       override legacy features. Use of this callback
+ *                             is highly discouraged. You should only need
+ *                             this if your hardware platform requires further
+ *                             custom fine tuning far beyong what may be
+ *                             possible in x86_early_init_platform_quirks() by
+ *                             only using the current x86_hardware_subarch
+ *                             semantics.
  */
 struct x86_platform_ops {
        unsigned long (*calibrate_tsc)(void);
@@ -165,6 +182,8 @@ struct x86_platform_ops {
        void (*save_sched_clock_state)(void);
        void (*restore_sched_clock_state)(void);
        void (*apic_post_init)(void);
+       struct x86_legacy_features legacy;
+       void (*set_legacy_features)(void);
 };
 
 struct pci_dev;
@@ -186,6 +205,8 @@ extern struct x86_cpuinit_ops x86_cpuinit;
 extern struct x86_platform_ops x86_platform;
 extern struct x86_msi_ops x86_msi;
 extern struct x86_io_apic_ops x86_io_apic_ops;
+
+extern void x86_early_init_platform_quirks(void);
 extern void x86_init_noop(void);
 extern void x86_init_uint_noop(unsigned int unused);
 

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 616ebd22ef9a2eee183dde7fae5bac7d03e28351..b81b22ee10bab783c11e6e4bda0793cf86727548 100644 (file)
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -2,7 +2,11 @@
 # Makefile for the linux kernel.
 #
 
-extra-y                := head_$(BITS).o head$(BITS).o head.o vmlinux.lds
+extra-y        := head_$(BITS).o
+extra-y        += head$(BITS).o
+extra-y        += head.o
+extra-y        += platform-quirks.o
+extra-y        += vmlinux.lds
 
 CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)
 

diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index 2911ef3a9f1c7bf11a2508a928cb216c5f48b6bc..d784bb547a9dd64f64ab0b9c429d7d0bff20df9d 100644 (file)
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -34,6 +34,8 @@ asmlinkage __visible void __init i386_start_kernel(void)
        cr4_init_shadow();
        sanitize_boot_params(&boot_params);
 
+       x86_early_init_platform_quirks();
+
        /* Call the subarch specific early setup function */
        switch (boot_params.hdr.hardware_subarch) {
        case X86_SUBARCH_INTEL_MID:

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 1f4422d5c8d013992d6b97a6a08734bde5bdb2b1..b72fb0b71dd1f84c7e9e8141281a82e758be9909 100644 (file)
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -182,6 +182,7 @@ void __init x86_64_start_reservations(char *real_mode_data)
        if (!boot_params.hdr.version)
                copy_bootdata(__va(real_mode_data));
 
+       x86_early_init_platform_quirks();
        reserve_ebda_region();
 
        switch (boot_params.hdr.hardware_subarch) {

diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c
new file mode 100644 (file)
index 0000000..021a5f9
--- /dev/null
+++ b/arch/x86/kernel/platform-quirks.c
@@ -0,0 +1,21 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+#include <asm/setup.h>
+#include <asm/bios_ebda.h>
+
+void __init x86_early_init_platform_quirks(void)
+{
+       x86_platform.legacy.rtc = 1;
+
+       switch (boot_params.hdr.hardware_subarch) {
+       case X86_SUBARCH_XEN:
+       case X86_SUBARCH_LGUEST:
+       case X86_SUBARCH_INTEL_MID:
+               x86_platform.legacy.rtc = 0;
+               break;
+       }
+
+       if (x86_platform.set_legacy_features)
+               x86_platform.set_legacy_features();
+}

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 4af8d063fb362cd2bf92b97a48fa8c1d5d95fd3b..62c48da3889db273e4915c86affd5636313c7c97 100644 (file)
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -14,6 +14,7 @@
 #include <asm/time.h>
 #include <asm/intel-mid.h>
 #include <asm/rtc.h>
+#include <asm/setup.h>
 
 #ifdef CONFIG_X86_32
 /*
@@ -188,10 +189,6 @@ static __init int add_rtc_cmos(void)
        if (of_have_populated_dt())
                return 0;
 
-       /* Intel MID platforms don't have ioport rtc */
-       if (intel_mid_identify_cpu())
-               return -ENODEV;
-
 #ifdef CONFIG_ACPI
        if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC) {
                /* This warning can likely go away again in a year or two. */
@@ -200,7 +197,7 @@ static __init int add_rtc_cmos(void)
        }
 #endif
 
-       if (paravirt_enabled() && !paravirt_has(RTC))
+       if (!x86_platform.legacy.rtc)
                return -ENODEV;
 
        platform_device_register(&rtc_device);

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index fd57d3ae7e16daf24f8cfdb4e708c5e4e9a9f3f9..f5497ee5fd2f53aa5bccf21ccd8a5ff23c7183fe 100644 (file)
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1414,7 +1414,6 @@ __init void lguest_init(void)
        pv_info.kernel_rpl = 1;
        /* Everyone except Xen runs with this set. */
        pv_info.shared_kernel_pmd = 1;
-       pv_info.features = 0;
 
        /*
         * We set up all the lguest overrides for sensitive operations.  These

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 61f4d9f67f60f85317d009296e759ebcc3b9c91d..752029d571bf9b69f9e6077829b7af78e972b691 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1193,7 +1193,6 @@ static const struct pv_info xen_info __initconst = {
 #ifdef CONFIG_X86_64
        .extra_user_64bit_cs = FLAT_USER_CS64,
 #endif
-       .features = 0,
        .name = "Xen",
 };
 
@@ -1506,6 +1505,11 @@ static void __init xen_pvh_early_guest_init(void)
 }
 #endif    /* CONFIG_XEN_PVH */
 
+static void __init xen_dom0_set_legacy_features(void)
+{
+       x86_platform.legacy.rtc = 1;
+}
+
 /* First C function to be called on Xen boot */
 asmlinkage __visible void __init xen_start_kernel(void)
 {
@@ -1527,8 +1531,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
        /* Install Xen paravirt ops */
        pv_info = xen_info;
-       if (xen_initial_domain())
-               pv_info.features |= PV_SUPPORTED_RTC;
        pv_init_ops = xen_init_ops;
        if (!xen_pvh_domain()) {
                pv_cpu_ops = xen_cpu_ops;
@@ -1688,6 +1690,8 @@ asmlinkage __visible void __init xen_start_kernel(void)
                        .u.firmware_info.type = XEN_FW_KBD_SHIFT_FLAGS,
                };
 
+               x86_platform.set_legacy_features =
+                               xen_dom0_set_legacy_features;
                xen_init_vga(info, xen_start_info->console.dom0.info_size);
                xen_start_info->console.domU.mfn = 0;
                xen_start_info->console.domU.evtchn = 0;