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authorJuergen Gross <jgross@suse.com>2022-09-26 12:33:03 +0200
committerJuergen Gross <jgross@suse.com>2022-10-11 10:50:58 +0200
commita1886b915e81439ba045b1431f3319d37ac1b906 (patch)
tree8587026743c091ad021176777a6a8d9a9ecadf45 /arch/x86
parentf90d98bdd06c0f3d1a60462c85324bd61f2a7142 (diff)
xen/pv: refactor msr access functions to support safe and unsafe accesses
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>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/xen/enlighten_pv.c75
1 files changed, 56 insertions, 19 deletions
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 0a5dcadf23b9..8c2acccebfe1 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -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;
+
+ if (HYPERVISOR_set_segment_base(which, base) == 0)
+ return;
- ret = 0;
+ 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;
-
- set:
- base = ((u64)high << 32) | low;
- if (HYPERVISOR_set_segment_base(which, base) != 0)
- ret = -EIO;
+ case MSR_FS_BASE:
+ set_seg(SEGBASE_FS, low, high, err);
+ break;
+
+ 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);
+ }
}
+}
+
+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 ret;
+ return err;
}
static u64 xen_read_msr(unsigned int msr)