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Commit dd2f4a00 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

x86/paravirt: Add paravirt_{read,write}_msr() 



This adds paravirt callbacks for unsafe MSR access.  On native, they
call native_{read,write}_msr().  On Xen, they use xen_{read,write}_msr_safe().

Nothing uses them yet for ease of bisection.  The next patch will
use them in rdmsrl(), wrmsrl(), etc.

I intentionally didn't make them warn on #GP on Xen.  I think that
should be done separately by the Xen maintainers.

Tested-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/880eebc5dcd2ad9f310d41345f82061ea500e9fa.1459605520.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent fbd70437

arch/x86/include/asm/msr.h

+3 −2
Original line number Diff line number Diff line
@@ -111,7 +111,8 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr, 
	return EAX_EDX_VAL(val, low, high);

}



static inline void native_write_msr(unsigned int msr,

/* Can be uninlined because referenced by paravirt */

notrace static inline void native_write_msr(unsigned int msr,

					    unsigned low, unsigned high)

{

	asm volatile("1: wrmsr\n"

arch/x86/include/asm/paravirt.h

+11 −0
Original line number Diff line number Diff line
@@ -130,6 +130,17 @@ static inline void wbinvd(void) 


#define get_kernel_rpl()  (pv_info.kernel_rpl)



static inline u64 paravirt_read_msr(unsigned msr)

{

	return PVOP_CALL1(u64, pv_cpu_ops.read_msr, msr);

}



static inline void paravirt_write_msr(unsigned msr,

				      unsigned low, unsigned high)

{

	return PVOP_VCALL3(pv_cpu_ops.write_msr, msr, low, high);

}



static inline u64 paravirt_read_msr_safe(unsigned msr, int *err)

{

	return PVOP_CALL2(u64, pv_cpu_ops.read_msr_safe, msr, err);

arch/x86/include/asm/paravirt_types.h

+8 −2
Original line number Diff line number Diff line
@@ -155,8 +155,14 @@ struct pv_cpu_ops { 
	void (*cpuid)(unsigned int *eax, unsigned int *ebx,

		      unsigned int *ecx, unsigned int *edx);



	/* MSR operations.

	   err = 0/-EIO.  wrmsr returns 0/-EIO. */

	/* Unsafe MSR operations.  These will warn or panic on failure. */

	u64 (*read_msr)(unsigned int msr);

	void (*write_msr)(unsigned int msr, unsigned low, unsigned high);



	/*

	 * Safe MSR operations.

	 * read sets err to 0 or -EIO.  write returns 0 or -EIO.

	 */

	u64 (*read_msr_safe)(unsigned int msr, int *err);

	int (*write_msr_safe)(unsigned int msr, unsigned low, unsigned high);

arch/x86/kernel/paravirt.c

+2 −0
Original line number Diff line number Diff line
@@ -339,6 +339,8 @@ __visible struct pv_cpu_ops pv_cpu_ops = { 
	.write_cr8 = native_write_cr8,

#endif

	.wbinvd = native_wbinvd,

	.read_msr = native_read_msr,

	.write_msr = native_write_msr,

	.read_msr_safe = native_read_msr_safe,

	.write_msr_safe = native_write_msr_safe,

	.read_pmc = native_read_pmc,

arch/x86/xen/enlighten.c

+23 −0
Original line number Diff line number Diff line
@@ -1092,6 +1092,26 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high) 
	return ret;

}



static u64 xen_read_msr(unsigned int msr)

{

	/*

	 * This will silently swallow a #GP from RDMSR.  It may be worth

	 * changing that.

	 */

	int err;



	return xen_read_msr_safe(msr, &err);

}



static void xen_write_msr(unsigned int msr, unsigned low, unsigned high)

{

	/*

	 * This will silently swallow a #GP from WRMSR.  It may be worth

	 * changing that.

	 */

	xen_write_msr_safe(msr, low, high);

}



void xen_setup_shared_info(void)

{

	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
@@ -1222,6 +1242,9 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = { 


	.wbinvd = native_wbinvd,



	.read_msr = xen_read_msr,

	.write_msr = xen_write_msr,



	.read_msr_safe = xen_read_msr_safe,

	.write_msr_safe = xen_write_msr_safe,