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Commit 1153968a authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
Browse files

xen: implement Xen write_msr operation 



64-bit uses MSRs for important things like the base for fs and
gs-prefixed addresses.  It's more efficient to use a hypercall to
update these, rather than go via the trap and emulate path.

Other MSR writes are just passed through; in an unprivileged domain
they do nothing, but it might be useful later.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bf18bf94

arch/x86/xen/enlighten.c

+30 −1
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ 
#include <asm/xen/hypervisor.h>

#include <asm/fixmap.h>

#include <asm/processor.h>

#include <asm/msr-index.h>

#include <asm/setup.h>

#include <asm/desc.h>

#include <asm/pgtable.h>
@@ -777,6 +778,34 @@ static void xen_write_cr3(unsigned long cr3) 
	xen_mc_issue(PARAVIRT_LAZY_CPU);  /* interrupts restored */

}



static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)

{

	int ret;



	ret = 0;



	switch(msr) {

#ifdef CONFIG_X86_64

		unsigned which;

		u64 base;



	case MSR_FS_BASE:		which = SEGBASE_FS; goto set;

	case MSR_KERNEL_GS_BASE:	which = SEGBASE_GS_USER; goto set;

	case MSR_GS_BASE:		which = SEGBASE_GS_KERNEL; goto set;



	set:

		base = ((u64)high << 32) | low;

		if (HYPERVISOR_set_segment_base(which, base) != 0)

			ret = -EFAULT;

		break;

#endif

	default:

		ret = native_write_msr_safe(msr, low, high);

	}



	return ret;

}



/* Early in boot, while setting up the initial pagetable, assume

   everything is pinned. */

static __init void xen_alloc_pte_init(struct mm_struct *mm, u32 pfn)
@@ -1165,7 +1194,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = { 
	.wbinvd = native_wbinvd,



	.read_msr = native_read_msr_safe,

	.write_msr = native_write_msr_safe,

	.write_msr = xen_write_msr_safe,

	.read_tsc = native_read_tsc,

	.read_pmc = native_read_pmc,