diff options
| author | Juergen Gross <jgross@suse.com> | 2021-01-20 14:55:44 +0100 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-02-10 12:25:49 +0100 |
| commit | 53c9d9240944088274aadbbbafc6138ca462db4f (patch) | |
| tree | 240f2116356d20534a96f21db21b469abcd64978 /arch/x86/include/asm | |
| parent | 5b4c6d65019bff65757f61adbbad5e45a333b800 (diff) | |
x86/pv: Switch SWAPGS to ALTERNATIVE
SWAPGS is used only for interrupts coming from user mode or for
returning to user mode. So there is no reason to use the PARAVIRT
framework, as it can easily be replaced by an ALTERNATIVE depending
on X86_FEATURE_XENPV.
There are several instances using the PV-aware SWAPGS macro in paths
which are never executed in a Xen PV guest. Replace those with the
plain swapgs instruction. For SWAPGS_UNSAFE_STACK the same applies.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210120135555.32594-5-jgross@suse.com
Diffstat (limited to 'arch/x86/include/asm')
| -rw-r--r-- | arch/x86/include/asm/irqflags.h | 20 | ||||
| -rw-r--r-- | arch/x86/include/asm/paravirt.h | 20 | ||||
| -rw-r--r-- | arch/x86/include/asm/paravirt_types.h | 2 |
3 files changed, 8 insertions, 34 deletions
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h index 2dfc8d380dab..8c86edefa115 100644 --- a/arch/x86/include/asm/irqflags.h +++ b/arch/x86/include/asm/irqflags.h @@ -131,18 +131,6 @@ static __always_inline unsigned long arch_local_irq_save(void) #define SAVE_FLAGS(x) pushfq; popq %rax #endif -#define SWAPGS swapgs -/* - * Currently paravirt can't handle swapgs nicely when we - * don't have a stack we can rely on (such as a user space - * stack). So we either find a way around these or just fault - * and emulate if a guest tries to call swapgs directly. - * - * Either way, this is a good way to document that we don't - * have a reliable stack. x86_64 only. - */ -#define SWAPGS_UNSAFE_STACK swapgs - #define INTERRUPT_RETURN jmp native_iret #define USERGS_SYSRET64 \ swapgs; \ @@ -170,6 +158,14 @@ static __always_inline int arch_irqs_disabled(void) return arch_irqs_disabled_flags(flags); } +#else +#ifdef CONFIG_X86_64 +#ifdef CONFIG_XEN_PV +#define SWAPGS ALTERNATIVE "swapgs", "", X86_FEATURE_XENPV +#else +#define SWAPGS swapgs +#endif +#endif #endif /* !__ASSEMBLY__ */ #endif diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index f8dce11d2bc1..f2ebe109a37e 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -776,26 +776,6 @@ extern void default_banner(void); #ifdef CONFIG_X86_64 #ifdef CONFIG_PARAVIRT_XXL -/* - * If swapgs is used while the userspace stack is still current, - * there's no way to call a pvop. The PV replacement *must* be - * inlined, or the swapgs instruction must be trapped and emulated. - */ -#define SWAPGS_UNSAFE_STACK \ - PARA_SITE(PARA_PATCH(PV_CPU_swapgs), swapgs) - -/* - * Note: swapgs is very special, and in practise is either going to be - * implemented with a single "swapgs" instruction or something very - * special. Either way, we don't need to save any registers for - * it. - */ -#define SWAPGS \ - PARA_SITE(PARA_PATCH(PV_CPU_swapgs), \ - ANNOTATE_RETPOLINE_SAFE; \ - call PARA_INDIRECT(pv_ops+PV_CPU_swapgs); \ - ) - #define USERGS_SYSRET64 \ PARA_SITE(PARA_PATCH(PV_CPU_usergs_sysret64), \ ANNOTATE_RETPOLINE_SAFE; \ diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index b6b02b7c19cc..130f428b0cc8 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -168,8 +168,6 @@ struct pv_cpu_ops { frame set up. */ void (*iret)(void); - void (*swapgs)(void); - void (*start_context_switch)(struct task_struct *prev); void (*end_context_switch)(struct task_struct *next); #endif |