On 04.10.2022 10:43, Juergen Gross wrote:
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@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Albeit ...
@@ -933,23 +937,39 @@ 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;
... I don't see a good reason to override the error code handed to us
by the hypervisor here; I do realize though that this ...
+ 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;
... was this way before.
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