[PATCH v2 11/12] x86/paravirt: Don't use pv_ops vector for MSR access functions

[Juergen Gross <jgross@xxxxxxxx>]

Instead of using the pv_ops vector for RDMSR/WRMSR related functions,
use a more explicit approach allowing to inline the RDMSR/WRMSR
instructions directly when not running as a Xen PV guest.

By using cpu_feature_enabled(X86_FEATURE_XENPV) for the Xen PV case
the related calls to Xen specific code will be statically disabled via
runtime patching.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- new patch
---
 arch/x86/include/asm/msr.h            | 57 ++++++++++++++++++++++-----
 arch/x86/include/asm/paravirt.h       | 45 ---------------------
 arch/x86/include/asm/paravirt_types.h | 13 ------
 arch/x86/kernel/paravirt.c            |  5 ---
 arch/x86/xen/enlighten_pv.c           | 20 ++++------
 arch/x86/xen/pmu.c                    |  1 +
 6 files changed, 57 insertions(+), 84 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index cc592611e333..d42cd2c19818 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -290,24 +290,22 @@ static __always_inline void native_wrmsr(u32 msr, u32 
low, u32 high)
        native_wrmsrq(msr, (u64)high << 32 | low);
 }
 
-static inline u64 native_read_msr(u32 msr)
+static __always_inline u64 native_read_msr(u32 msr)
 {
        return native_rdmsrq(msr);
 }
 
-static inline int native_read_msr_safe(u32 msr, u64 *val)
+static __always_inline int native_read_msr_safe(u32 msr, u64 *val)
 {
        return __rdmsr(msr, val, EX_TYPE_RDMSR_SAFE) ? -EIO : 0;
 }
 
-/* Can be uninlined because referenced by paravirt */
-static inline void notrace native_write_msr(u32 msr, u64 val)
+static __always_inline void native_write_msr(u32 msr, u64 val)
 {
        native_wrmsrq(msr, val);
 }
 
-/* Can be uninlined because referenced by paravirt */
-static inline int notrace native_write_msr_safe(u32 msr, u64 val)
+static __always_inline int native_write_msr_safe(u32 msr, u64 val)
 {
        return __wrmsrq(msr, val, EX_TYPE_WRMSR_SAFE) ? -EIO : 0;
 }
@@ -325,8 +323,49 @@ static inline u64 native_read_pmc(int counter)
        return EAX_EDX_VAL(val, low, high);
 }
 
-#ifdef CONFIG_PARAVIRT_XXL
-#include <asm/paravirt.h>
+#ifdef CONFIG_XEN_PV
+#include <asm/xen/msr.h>
+
+static __always_inline u64 read_msr(u32 msr)
+{
+       if (cpu_feature_enabled(X86_FEATURE_XENPV))
+               return xen_read_msr(msr);
+
+       return native_rdmsrq(msr);
+}
+
+static __always_inline int read_msr_safe(u32 msr, u64 *p)
+{
+       if (cpu_feature_enabled(X86_FEATURE_XENPV))
+               return xen_read_msr_safe(msr, p);
+
+       return native_read_msr_safe(msr, p);
+}
+
+static __always_inline void write_msr(u32 msr, u64 val)
+{
+       if (cpu_feature_enabled(X86_FEATURE_XENPV))
+               xen_write_msr(msr, val);
+       else
+               native_wrmsrq(msr, val);
+}
+
+static __always_inline int write_msr_safe(u32 msr, u64 val)
+{
+       if (cpu_feature_enabled(X86_FEATURE_XENPV))
+               return xen_write_msr_safe(msr, val);
+
+       return native_write_msr_safe(msr, val);
+}
+
+static __always_inline u64 rdpmc(int counter)
+{
+       if (cpu_feature_enabled(X86_FEATURE_XENPV))
+               return xen_read_pmc(counter);
+
+       return native_read_pmc(counter);
+}
+
 #else
 static __always_inline u64 read_msr(u32 msr)
 {
@@ -353,7 +392,7 @@ static __always_inline u64 rdpmc(int counter)
        return native_read_pmc(counter);
 }
 
-#endif /* !CONFIG_PARAVIRT_XXL */
+#endif /* !CONFIG_XEN_PV */
 
 /*
  * Access to machine-specific registers (available on 586 and better only)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index dc297f62b935..45f47b7d9f56 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -175,51 +175,6 @@ static inline void __write_cr4(unsigned long x)
        PVOP_VCALL1(cpu.write_cr4, x);
 }
 
-static inline u64 paravirt_read_msr(u32 msr)
-{
-       return PVOP_CALL1(u64, cpu.read_msr, msr);
-}
-
-static inline void paravirt_write_msr(u32 msr, u64 val)
-{
-       PVOP_VCALL2(cpu.write_msr, msr, val);
-}
-
-static inline int paravirt_read_msr_safe(u32 msr, u64 *val)
-{
-       return PVOP_CALL2(int, cpu.read_msr_safe, msr, val);
-}
-
-static inline int paravirt_write_msr_safe(u32 msr, u64 val)
-{
-       return PVOP_CALL2(int, cpu.write_msr_safe, msr, val);
-}
-
-static __always_inline u64 read_msr(u32 msr)
-{
-       return paravirt_read_msr(msr);
-}
-
-static __always_inline int read_msr_safe(u32 msr, u64 *p)
-{
-       return paravirt_read_msr_safe(msr, p);
-}
-
-static __always_inline void write_msr(u32 msr, u64 val)
-{
-       paravirt_write_msr(msr, val);
-}
-
-static __always_inline int write_msr_safe(u32 msr, u64 val)
-{
-       return paravirt_write_msr_safe(msr, val);
-}
-
-static __always_inline u64 rdpmc(int counter)
-{
-       return PVOP_CALL1(u64, cpu.read_pmc, counter);
-}
-
 static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned 
entries)
 {
        PVOP_VCALL2(cpu.alloc_ldt, ldt, entries);
diff --git a/arch/x86/include/asm/paravirt_types.h 
b/arch/x86/include/asm/paravirt_types.h
index 37a8627d8277..0d03e658ea8f 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -90,19 +90,6 @@ struct pv_cpu_ops {
        void (*cpuid)(unsigned int *eax, unsigned int *ebx,
                      unsigned int *ecx, unsigned int *edx);
 
-       /* Unsafe MSR operations.  These will warn or panic on failure. */
-       u64 (*read_msr)(u32 msr);
-       void (*write_msr)(u32 msr, u64 val);
-
-       /*
-        * Safe MSR operations.
-        * Returns 0 or -EIO.
-        */
-       int (*read_msr_safe)(u32 msr, u64 *val);
-       int (*write_msr_safe)(u32 msr, u64 val);
-
-       u64 (*read_pmc)(int counter);
-
        void (*start_context_switch)(struct task_struct *prev);
        void (*end_context_switch)(struct task_struct *next);
 #endif
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index ab3e172dcc69..240eeb1beab5 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -129,11 +129,6 @@ struct paravirt_patch_template pv_ops = {
        .cpu.read_cr0           = native_read_cr0,
        .cpu.write_cr0          = native_write_cr0,
        .cpu.write_cr4          = native_write_cr4,
-       .cpu.read_msr           = native_read_msr,
-       .cpu.write_msr          = native_write_msr,
-       .cpu.read_msr_safe      = native_read_msr_safe,
-       .cpu.write_msr_safe     = native_write_msr_safe,
-       .cpu.read_pmc           = native_read_pmc,
        .cpu.load_tr_desc       = native_load_tr_desc,
        .cpu.set_ldt            = native_set_ldt,
        .cpu.load_gdt           = native_load_gdt,
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 26bbaf4b7330..df653099c567 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1160,15 +1160,16 @@ static void xen_do_write_msr(u32 msr, u64 val, int *err)
        }
 }
 
-static int xen_read_msr_safe(u32 msr, u64 *val)
+int xen_read_msr_safe(u32 msr, u64 *val)
 {
        int err = 0;
 
        *val = xen_do_read_msr(msr, &err);
        return err;
 }
+EXPORT_SYMBOL(xen_read_msr_safe);
 
-static int xen_write_msr_safe(u32 msr, u64 val)
+int xen_write_msr_safe(u32 msr, u64 val)
 {
        int err = 0;
 
@@ -1176,20 +1177,23 @@ static int xen_write_msr_safe(u32 msr, u64 val)
 
        return err;
 }
+EXPORT_SYMBOL(xen_write_msr_safe);
 
-static u64 xen_read_msr(u32 msr)
+u64 xen_read_msr(u32 msr)
 {
        int err = 0;
 
        return xen_do_read_msr(msr, xen_msr_safe ? &err : NULL);
 }
+EXPORT_SYMBOL(xen_read_msr);
 
-static void xen_write_msr(u32 msr, u64 val)
+void xen_write_msr(u32 msr, u64 val)
 {
        int err;
 
        xen_do_write_msr(msr, val, xen_msr_safe ? &err : NULL);
 }
+EXPORT_SYMBOL(xen_write_msr);
 
 /* This is called once we have the cpu_possible_mask */
 void __init xen_setup_vcpu_info_placement(void)
@@ -1225,14 +1229,6 @@ static const typeof(pv_ops) xen_cpu_ops __initconst = {
 
                .write_cr4 = xen_write_cr4,
 
-               .read_msr = xen_read_msr,
-               .write_msr = xen_write_msr,
-
-               .read_msr_safe = xen_read_msr_safe,
-               .write_msr_safe = xen_write_msr_safe,
-
-               .read_pmc = xen_read_pmc,
-
                .load_tr_desc = paravirt_nop,
                .set_ldt = xen_set_ldt,
                .load_gdt = xen_load_gdt,
diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c
index d49a3bdc448b..d0dea950cd4f 100644
--- a/arch/x86/xen/pmu.c
+++ b/arch/x86/xen/pmu.c
@@ -370,6 +370,7 @@ u64 xen_read_pmc(int counter)
        else
                return xen_intel_read_pmc(counter);
 }
+EXPORT_SYMBOL(xen_read_pmc);
 
 int pmu_apic_update(uint32_t val)
 {
-- 
2.51.0