x86/entry/64/paravirt: Use paravirt-safe macro to access eflags

Commit 1d3e53e8624a ("x86/entry/64: Refactor IRQ stacks and make them
NMI-safe") added DEBUG_ENTRY_ASSERT_IRQS_OFF macro that acceses eflags
using 'pushfq' instruction when testing for IF bit. On PV Xen guests
looking at IF flag directly will always see it set, resulting in 'ud2'.

Introduce SAVE_FLAGS() macro that will use appropriate save_fl pv op when
running paravirt.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: xen-devel@lists.xenproject.org
Link: https://lkml.kernel.org/r/20171204150604.899457242@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index a2b30ec69497277f39ef56e0dfad604170f78c19..32306788821c82f094806eedf0fae74ff283c4ad 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -462,12 +462,13 @@ END(irq_entries_start)
 
 .macro DEBUG_ENTRY_ASSERT_IRQS_OFF
 #ifdef CONFIG_DEBUG_ENTRY
-       pushfq
-       testl $X86_EFLAGS_IF, (%rsp)
+       pushq %rax
+       SAVE_FLAGS(CLBR_RAX)
+       testl $X86_EFLAGS_IF, %eax
        jz .Lokay_\@
        ud2
 .Lokay_\@:
-       addq $8, %rsp
+       popq %rax
 #endif
 .endm
 

diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index c8ef23f2c28f17c59308b9c41179c47f85e075ad..89f08955fff733c688a5ce4f4a0b8d74050ee617 100644 (file)
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -142,6 +142,9 @@ static inline notrace unsigned long arch_local_irq_save(void)
        swapgs;                                 \
        sysretl
 
+#ifdef CONFIG_DEBUG_ENTRY
+#define SAVE_FLAGS(x)          pushfq; popq %rax
+#endif
 #else
 #define INTERRUPT_RETURN               iret
 #define ENABLE_INTERRUPTS_SYSEXIT      sti; sysexit

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 283efcaac8aff86f2c004bc23e4b8642cbf3d527..892df375b6155a51f584760efb9f9e77c3f732e8 100644 (file)
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -927,6 +927,15 @@ extern void default_banner(void);
        PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret64),       \
                  CLBR_NONE,                                            \
                  jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usergs_sysret64))
+
+#ifdef CONFIG_DEBUG_ENTRY
+#define SAVE_FLAGS(clobbers)                                        \
+       PARA_SITE(PARA_PATCH(pv_irq_ops, PV_IRQ_save_fl), clobbers, \
+                 PV_SAVE_REGS(clobbers | CLBR_CALLEE_SAVE);        \
+                 call PARA_INDIRECT(pv_irq_ops+PV_IRQ_save_fl);    \
+                 PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);)
+#endif
+
 #endif /* CONFIG_X86_32 */
 
 #endif /* __ASSEMBLY__ */

diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 630212fa9b9da3f0498fc30d4c193c5926c43abb..e3a5175a444bc03499602054b54ac4f9eff977c2 100644 (file)
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -23,6 +23,9 @@ int main(void)
 #ifdef CONFIG_PARAVIRT
        OFFSET(PV_CPU_usergs_sysret64, pv_cpu_ops, usergs_sysret64);
        OFFSET(PV_CPU_swapgs, pv_cpu_ops, swapgs);
+#ifdef CONFIG_DEBUG_ENTRY
+       OFFSET(PV_IRQ_save_fl, pv_irq_ops, save_fl);
+#endif
        BLANK();
 #endif