x86: adds paravirt hook for swapgs

This patch adds paravirt hook for swapgs operation, which is a privileged
operation in x86_64.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 072c1a08efe6..e7c17cc4a99e 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -390,6 +390,7 @@ struct pv_cpu_ops pv_cpu_ops = {
 
         .irq_enable_syscall_ret = native_irq_enable_syscall_ret,
         .iret = native_iret,
+        .swapgs = native_swapgs,
 
         .set_iopl_mask = native_set_iopl_mask,
         .io_delay = native_io_delay,
diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h
index 7d1c126e2249..e8fbf742d425 100644
--- a/include/asm-x86/paravirt.h
+++ b/include/asm-x86/paravirt.h
@@ -127,6 +127,8 @@ struct pv_cpu_ops {
         void (*irq_enable_syscall_ret)(void);
         void (*iret)(void);
 
+        void (*swapgs)(void);
+
         struct pv_lazy_ops lazy_mode;
 };
 
@@ -1228,6 +1230,13 @@ static inline unsigned long __raw_local_irq_save(void)
         call *pv_cpu_ops+PV_CPU_read_cr0;       \
         pop %edx; pop %ecx
 #else
+#define SWAPGS                                                          \
+        PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_swapgs), CLBR_NONE,     \
+                  PV_SAVE_REGS;                                         \
+                  call *pv_cpu_ops+PV_CPU_swapgs;                       \
+                  PV_RESTORE_REGS                                       \
+                 )
+
 #define GET_CR2_INTO_RCX                        \
         call *pv_mmu_ops+PV_MMU_read_cr2;       \
         movq %rax, %rcx;                        \
diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h
index e6fa06fee72a..72740c6f1109 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -435,6 +435,13 @@ static inline void native_load_sp0(struct tss_struct *tss,
 #endif
 }
 
+static inline void native_swapgs(void)
+{
+#ifdef CONFIG_X86_64
+        asm volatile("swapgs" ::: "memory");
+#endif
+}
+
 #ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
 #else
@@ -456,6 +463,7 @@ static inline void load_sp0(struct tss_struct *tss,
 }
 
 #define set_iopl_mask native_set_iopl_mask
+#define SWAPGS  swapgs
 #endif /* CONFIG_PARAVIRT */
 
 /*