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xen/pv: refactor msr access functions to support safe and unsafe accesses

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Refactor and rename xen_read_msr_safe() and xen_write_msr_safe() to
support both cases of MSR accesses, safe ones and potentially GP-fault
generating ones.

This will prepare to no longer swallow GPs silently in xen_read_msr()
and xen_write_msr().

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Juergen Gross 2022-09-26 12:33:03 +02:00
parent f90d98bdd0
commit a1886b915e
1 changed files with 55 additions and 18 deletions
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73
arch/x86/xen/enlighten_pv.c
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@ -916,14 +916,18 @@ static void xen_write_cr4(unsigned long cr4)
native_write_cr4(cr4);
}
static u64 xen_read_msr_safe(unsigned int msr, int *err)
static u64 xen_do_read_msr(unsigned int msr, int *err)
{
u64 val;
u64 val = 0; /* Avoid uninitialized value for safe variant. */
if (pmu_msr_read(msr, &val, err))
return val;
val = native_read_msr_safe(msr, err);
if (err)
val = native_read_msr_safe(msr, err);
else
val = native_read_msr(msr);
switch (msr) {
case MSR_IA32_APICBASE:
val &= ~X2APIC_ENABLE;
@ -932,23 +936,39 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err)
return val;
}
static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
static void set_seg(unsigned int which, unsigned int low, unsigned int high,
int *err)
{
int ret;
unsigned int which;
u64 base;
u64 base = ((u64)high << 32) | low;
ret = 0;
if (HYPERVISOR_set_segment_base(which, base) == 0)
return;
if (err)
*err = -EIO;
else
WARN(1, "Xen set_segment_base(%u, %llx) failed\n", which, base);
}
/*
* Support write_msr_safe() and write_msr() semantics.
* With err == NULL write_msr() semantics are selected.
* Supplying an err pointer requires err to be pre-initialized with 0.
*/
static void xen_do_write_msr(unsigned int msr, unsigned int low,
unsigned int high, int *err)
{
switch (msr) {
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;
case MSR_FS_BASE:
set_seg(SEGBASE_FS, low, high, err);
break;
set:
base = ((u64)high << 32) | low;
if (HYPERVISOR_set_segment_base(which, base) != 0)
ret = -EIO;
case MSR_KERNEL_GS_BASE:
set_seg(SEGBASE_GS_USER, low, high, err);
break;
case MSR_GS_BASE:
set_seg(SEGBASE_GS_KERNEL, low, high, err);
break;
case MSR_STAR:
@ -964,11 +984,28 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
break;
default:
if (!pmu_msr_write(msr, low, high, &ret))
ret = native_write_msr_safe(msr, low, high);
if (!pmu_msr_write(msr, low, high, err)) {
if (err)
*err = native_write_msr_safe(msr, low, high);
else
native_write_msr(msr, low, high);
}
}
}
return ret;
static u64 xen_read_msr_safe(unsigned int msr, int *err)
{
return xen_do_read_msr(msr, err);
}
static int xen_write_msr_safe(unsigned int msr, unsigned int low,
unsigned int high)
{
int err = 0;
xen_do_write_msr(msr, low, high, &err);
return err;
}
static u64 xen_read_msr(unsigned int msr)