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xen: implement Xen write_msr operation

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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: Jeremy 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge 2008-07-08 15:07:16 -07:00 committed by Ingo Molnar
parent bf18bf94dc
commit 1153968a48
1 changed files with 30 additions and 1 deletions
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31
arch/x86/xen/enlighten.c
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@ -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,