From: Juergen Gross jgross@suse.com
stable inclusion from stable-v5.10.84 commit 4bbbc9c4f313351b5c087b2135fb232dd0bdd41d bugzilla: 186030 https://gitee.com/openeuler/kernel/issues/I4QV2F
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit 53c9d9240944088274aadbbbafc6138ca462db4f ]
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 Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Chen Jun chenjun102@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- arch/x86/entry/entry_64.S | 10 +++++----- arch/x86/include/asm/irqflags.h | 20 ++++++++------------ arch/x86/include/asm/paravirt.h | 20 -------------------- arch/x86/include/asm/paravirt_types.h | 2 -- arch/x86/kernel/asm-offsets_64.c | 1 - arch/x86/kernel/paravirt.c | 1 - arch/x86/kernel/paravirt_patch.c | 3 --- arch/x86/xen/enlighten_pv.c | 3 --- 8 files changed, 13 insertions(+), 47 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index de541ea2788e..166554a109ae 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -673,7 +673,7 @@ native_irq_return_ldt: */
pushq %rdi /* Stash user RDI */ - SWAPGS /* to kernel GS */ + swapgs /* to kernel GS */ SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi /* to kernel CR3 */
movq PER_CPU_VAR(espfix_waddr), %rdi @@ -703,7 +703,7 @@ native_irq_return_ldt: orq PER_CPU_VAR(espfix_stack), %rax
SWITCH_TO_USER_CR3_STACK scratch_reg=%rdi - SWAPGS /* to user GS */ + swapgs /* to user GS */ popq %rdi /* Restore user RDI */
movq %rax, %rsp @@ -947,7 +947,7 @@ SYM_CODE_START_LOCAL(paranoid_entry) ret
.Lparanoid_entry_swapgs: - SWAPGS + swapgs
/* * The above SAVE_AND_SWITCH_TO_KERNEL_CR3 macro doesn't do an @@ -1005,7 +1005,7 @@ SYM_CODE_START_LOCAL(paranoid_exit) jnz restore_regs_and_return_to_kernel
/* We are returning to a context with user GSBASE */ - SWAPGS_UNSAFE_STACK + swapgs jmp restore_regs_and_return_to_kernel SYM_CODE_END(paranoid_exit)
@@ -1431,7 +1431,7 @@ nmi_no_fsgsbase: jnz nmi_restore
nmi_swapgs: - SWAPGS_UNSAFE_STACK + swapgs
nmi_restore: POP_REGS 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 5a8769a77234..ef778b87f463 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 17a2308ef3af..b30b56d47619 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -171,8 +171,6 @@ 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 diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c index 828be792231e..1354bc30614d 100644 --- a/arch/x86/kernel/asm-offsets_64.c +++ b/arch/x86/kernel/asm-offsets_64.c @@ -15,7 +15,6 @@ int main(void) #ifdef CONFIG_PARAVIRT_XXL OFFSET(PV_CPU_usergs_sysret64, paravirt_patch_template, cpu.usergs_sysret64); - OFFSET(PV_CPU_swapgs, paravirt_patch_template, cpu.swapgs); #ifdef CONFIG_DEBUG_ENTRY OFFSET(PV_IRQ_save_fl, paravirt_patch_template, irq.save_fl); #endif diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index f18ff94b0202..f847e332b268 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -312,7 +312,6 @@ struct paravirt_patch_template pv_ops = {
.cpu.usergs_sysret64 = native_usergs_sysret64, .cpu.iret = native_iret, - .cpu.swapgs = native_swapgs,
#ifdef CONFIG_X86_IOPL_IOPERM .cpu.invalidate_io_bitmap = native_tss_invalidate_io_bitmap, diff --git a/arch/x86/kernel/paravirt_patch.c b/arch/x86/kernel/paravirt_patch.c index ace6e334cb39..7c518b08aa3c 100644 --- a/arch/x86/kernel/paravirt_patch.c +++ b/arch/x86/kernel/paravirt_patch.c @@ -28,7 +28,6 @@ struct patch_xxl { const unsigned char irq_restore_fl[2]; const unsigned char cpu_wbinvd[2]; const unsigned char cpu_usergs_sysret64[6]; - const unsigned char cpu_swapgs[3]; const unsigned char mov64[3]; };
@@ -43,7 +42,6 @@ static const struct patch_xxl patch_data_xxl = { .cpu_wbinvd = { 0x0f, 0x09 }, // wbinvd .cpu_usergs_sysret64 = { 0x0f, 0x01, 0xf8, 0x48, 0x0f, 0x07 }, // swapgs; sysretq - .cpu_swapgs = { 0x0f, 0x01, 0xf8 }, // swapgs .mov64 = { 0x48, 0x89, 0xf8 }, // mov %rdi, %rax };
@@ -86,7 +84,6 @@ unsigned int native_patch(u8 type, void *insn_buff, unsigned long addr, PATCH_CASE(mmu, write_cr3, xxl, insn_buff, len);
PATCH_CASE(cpu, usergs_sysret64, xxl, insn_buff, len); - PATCH_CASE(cpu, swapgs, xxl, insn_buff, len); PATCH_CASE(cpu, wbinvd, xxl, insn_buff, len); #endif
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 5af0421ef74b..16ff25d6935e 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1083,9 +1083,6 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = { #endif .io_delay = xen_io_delay,
- /* Xen takes care of %gs when switching to usermode for us */ - .swapgs = paravirt_nop, - .start_context_switch = paravirt_start_context_switch, .end_context_switch = xen_end_context_switch, };