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Commit 55aedddb authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

x86/paravirt: Make read_cr2() CALLEE_SAVE 



The one paravirt read_cr2() implementation (Xen) is actually quite trivial
and doesn't need to clobber anything other than the return register.

Making read_cr2() CALLEE_SAVE avoids all the PUSH/POP nonsense and allows
more convenient use from assembly.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Cc: bp@alien8.de
Cc: rostedt@goodmis.org
Cc: luto@kernel.org
Cc: torvalds@linux-foundation.org
Cc: hpa@zytor.com
Cc: dave.hansen@linux.intel.com
Cc: zhe.he@windriver.com
Cc: joel@joelfernandes.org
Cc: devel@etsukata.com
Link: https://lkml.kernel.org/r/20190711114335.887392493@infradead.org
parent 406de552

arch/x86/entry/calling.h

+6 −0
Original line number Diff line number Diff line
@@ -343,3 +343,9 @@ For 32-bit we have the following conventions - kernel is built with 
.Lafter_call_\@:

#endif

.endm



#ifdef CONFIG_PARAVIRT_XXL

#define GET_CR2_INTO(reg) GET_CR2_INTO_AX ; _ASM_MOV %_ASM_AX, reg

#else

#define GET_CR2_INTO(reg) _ASM_MOV %cr2, reg

#endif

arch/x86/include/asm/paravirt.h

+13 −9
Original line number Diff line number Diff line
@@ -116,7 +116,7 @@ static inline void write_cr0(unsigned long x) 


static inline unsigned long read_cr2(void)

{

	return PVOP_CALL0(unsigned long, mmu.read_cr2);

	return PVOP_CALLEE0(unsigned long, mmu.read_cr2);

}



static inline void write_cr2(unsigned long x)
@@ -909,13 +909,7 @@ extern void default_banner(void); 
		  ANNOTATE_RETPOLINE_SAFE;				\

		  call PARA_INDIRECT(pv_ops+PV_CPU_swapgs);		\

		 )

#endif



#define GET_CR2_INTO_RAX				\

	ANNOTATE_RETPOLINE_SAFE;				\

	call PARA_INDIRECT(pv_ops+PV_MMU_read_cr2);



#ifdef CONFIG_PARAVIRT_XXL

#define USERGS_SYSRET64							\

	PARA_SITE(PARA_PATCH(PV_CPU_usergs_sysret64),			\

		  ANNOTATE_RETPOLINE_SAFE;				\
@@ -929,9 +923,19 @@ extern void default_banner(void); 
		  call PARA_INDIRECT(pv_ops+PV_IRQ_save_fl);	    \

		  PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);)

#endif

#endif

#endif /* CONFIG_PARAVIRT_XXL */

#endif	/* CONFIG_X86_64 */



#ifdef CONFIG_PARAVIRT_XXL



#define GET_CR2_INTO_AX							\

	PARA_SITE(PARA_PATCH(PV_MMU_read_cr2),				\

		  ANNOTATE_RETPOLINE_SAFE;				\

		  call PARA_INDIRECT(pv_ops+PV_MMU_read_cr2);		\

		 )



#endif /* CONFIG_PARAVIRT_XXL */



#endif	/* CONFIG_X86_32 */



#endif /* __ASSEMBLY__ */

#else  /* CONFIG_PARAVIRT */

arch/x86/include/asm/paravirt_types.h

+1 −1
Original line number Diff line number Diff line
@@ -220,7 +220,7 @@ struct pv_mmu_ops { 
	void (*exit_mmap)(struct mm_struct *mm);



#ifdef CONFIG_PARAVIRT_XXL

	unsigned long (*read_cr2)(void);

	struct paravirt_callee_save read_cr2;

	void (*write_cr2)(unsigned long);



	unsigned long (*read_cr3)(void);

arch/x86/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -76,6 +76,7 @@ static void __used common(void) 
	BLANK();

	OFFSET(XEN_vcpu_info_mask, vcpu_info, evtchn_upcall_mask);

	OFFSET(XEN_vcpu_info_pending, vcpu_info, evtchn_upcall_pending);

	OFFSET(XEN_vcpu_info_arch_cr2, vcpu_info, arch.cr2);

#endif



	BLANK();

arch/x86/kernel/head_64.S

+1 −3
Original line number Diff line number Diff line
@@ -29,9 +29,7 @@ 
#ifdef CONFIG_PARAVIRT_XXL

#include <asm/asm-offsets.h>

#include <asm/paravirt.h>

#define GET_CR2_INTO(reg) GET_CR2_INTO_RAX ; movq %rax, reg

#else

#define GET_CR2_INTO(reg) movq %cr2, reg

#define INTERRUPT_RETURN iretq

#endif
@@ -323,7 +321,7 @@ early_idt_handler_common: 


	cmpq $14,%rsi		/* Page fault? */

	jnz 10f

	GET_CR2_INTO(%rdi)	/* Can clobber any volatile register if pv */

	GET_CR2_INTO(%rdi)	/* can clobber %rax if pv */

	call early_make_pgtable

	andl %eax,%eax

	jz 20f			/* All good */