[PATCH v5 09/12] x86/paravirt: switch iret pvops to ALTERNATIVE

Juergen Gross
2021-03-08T12:29:58Z

The iret paravirt op is rather special as it is using a jmp instead
of a call instruction. Switch it to ALTERNATIVE.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- use ALTERNATIVE_TERNARY
---
arch/x86/include/asm/paravirt.h | 6 +++---
arch/x86/include/asm/paravirt_types.h | 5 +----
arch/x86/kernel/asm-offsets.c | 5 -----
arch/x86/kernel/paravirt.c | 26 ++------------------------
arch/x86/xen/enlighten_pv.c | 3 +--
5 files changed, 7 insertions(+), 38 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index c6496a82fad1..36cd71fa097f 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -749,9 +749,9 @@ extern void default_banner(void);
#define PARA_INDIRECT(addr) *addr(%rip)

#define INTERRUPT_RETURN \
- PARA_SITE(PARA_PATCH(PV_CPU_iret), \
- ANNOTATE_RETPOLINE_SAFE; \
- jmp PARA_INDIRECT(pv_ops+PV_CPU_iret);)
+ ANNOTATE_RETPOLINE_SAFE; \
+ ALTERNATIVE_TERNARY("jmp *paravirt_iret(%rip);", \
+ X86_FEATURE_XENPV, "jmp xen_iret;", "jmp native_iret;")

#ifdef CONFIG_DEBUG_ENTRY
#define SAVE_FLAGS(clobbers) \
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 45bd21647dd8..0afdac83f926 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -151,10 +151,6 @@ struct pv_cpu_ops {

u64 (*read_pmc)(int counter);

- /* Normal iret. Jump to this with the standard iret stack
- frame set up. */
- void (*iret)(void);
-
void (*start_context_switch)(struct task_struct *prev);
void (*end_context_switch)(struct task_struct *next);
#endif
@@ -294,6 +290,7 @@ struct paravirt_patch_template {

extern struct pv_info pv_info;
extern struct paravirt_patch_template pv_ops;
+extern void (*paravirt_iret)(void);

#define PARAVIRT_PATCH(x) \
(offsetof(struct paravirt_patch_template, x) / sizeof(void *))
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 736508004b30..ecd3fd6993d1 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -61,11 +61,6 @@ static void __used common(void)
OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe_ia32, uc.uc_mcontext);
#endif

-#ifdef CONFIG_PARAVIRT_XXL
- BLANK();
- OFFSET(PV_CPU_iret, paravirt_patch_template, cpu.iret);
-#endif
-
#ifdef CONFIG_XEN
BLANK();
OFFSET(XEN_vcpu_info_mask, vcpu_info, evtchn_upcall_mask);
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 44e5b0fe28cb..0553a339d850 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -86,25 +86,6 @@ u64 notrace _paravirt_ident_64(u64 x)
{
return x;
}
-
-static unsigned paravirt_patch_jmp(void *insn_buff, const void *target,
- unsigned long addr, unsigned len)
-{
- struct branch *b = insn_buff;
- unsigned long delta = (unsigned long)target - (addr+5);
-
- if (len < 5) {
-#ifdef CONFIG_RETPOLINE
- WARN_ONCE(1, "Failing to patch indirect JMP in %ps\n", (void *)addr);
-#endif
- return len; /* call too long for patch site */
- }
-
- b->opcode = 0xe9; /* jmp */
- b->delta = delta;
-
- return 5;
-}
#endif

DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
@@ -136,9 +117,6 @@ unsigned paravirt_patch_default(u8 type, void *insn_buff,
else if (opfunc == _paravirt_ident_64)
ret = paravirt_patch_ident_64(insn_buff, len);

- else if (type == PARAVIRT_PATCH(cpu.iret))
- /* If operation requires a jmp, then jmp */
- ret = paravirt_patch_jmp(insn_buff, opfunc, addr, len);
#endif
else
/* Otherwise call the function. */
@@ -316,8 +294,6 @@ struct paravirt_patch_template pv_ops = {

.cpu.load_sp0 = native_load_sp0,

- .cpu.iret = native_iret,
-
#ifdef CONFIG_X86_IOPL_IOPERM
.cpu.invalidate_io_bitmap = native_tss_invalidate_io_bitmap,
.cpu.update_io_bitmap = native_tss_update_io_bitmap,
@@ -422,6 +398,8 @@ struct paravirt_patch_template pv_ops = {
NOKPROBE_SYMBOL(native_get_debugreg);
NOKPROBE_SYMBOL(native_set_debugreg);
NOKPROBE_SYMBOL(native_load_idt);
+
+void (*paravirt_iret)(void) = native_iret;
#endif

EXPORT_SYMBOL(pv_ops);
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index dc0a337f985b..08dca7bebb30 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1070,8 +1070,6 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {

.read_pmc = xen_read_pmc,

- .iret = xen_iret,
-
.load_tr_desc = paravirt_nop,
.set_ldt = xen_set_ldt,
.load_gdt = xen_load_gdt,
@@ -1235,6 +1233,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
pv_info = xen_info;
pv_ops.init.patch = paravirt_patch_default;
pv_ops.cpu = xen_cpu_ops;
+ paravirt_iret = xen_iret;
xen_init_irq_ops();

/*
--
2.26.2