x86: allow VCPUOP_register_vcpu_info to work again on PVHVM guests

For details on the hypercall please see commit
c58ae69360ccf2495a19bf4ca107e21cf873c75b (VCPUOP_register_vcpu_info) and
the c/s 23143 (git commit 6b063a4a6f44245a727aa04ef76408b2e00af9c7)
(x86: move pv-only members of struct vcpu to struct pv_vcpu)
that introduced the regression.

The current code allows the PVHVM guest to make this hypercall.
But for PVHVM guest it always returns -EINVAL (-22) for Xen 4.2
and above. Xen 4.1 and earlier worked.

The reason is that the check in map_vcpu_info would fail
at:

  if ( v->arch.vcpu_info_mfn != INVALID_MFN )

The reason is that the vcpu_info_mfn for PVHVM guests ends up by
defualt with the value of zero (introduced by c/s 23143).

The code in vcpu_initialise which initialized vcpu_info_mfn to a
valid value (INVALID_MFN), would never be called for PVHVM:

    if ( is_hvm_domain(d) )
    {
        rc = hvm_vcpu_initialise(v);
        goto done;
    }

    v->arch.pv_vcpu.vcpu_info_mfn = INVALID_MFN;

while previously it would be:

     v->arch.vcpu_info_mfn = INVALID_MFN;

[right at the start of the function in Xen 4.1]

This fixes the problem with Linux advertising this error:
register_vcpu_info failed: err=-22

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index 6f9744a58f..bdaf714ef6 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -374,9 +374,6 @@ struct pv_vcpu
     /* Current LDT details. */
     unsigned long shadow_ldt_mapcnt;
     spinlock_t shadow_ldt_lock;
-
-    /* Guest-specified relocation of vcpu_info. */
-    unsigned long vcpu_info_mfn;
 };
 
 struct arch_vcpu
@@ -438,6 +435,9 @@ struct arch_vcpu
 
     struct paging_vcpu paging;
 
+    /* Guest-specified relocation of vcpu_info. */
+    unsigned long vcpu_info_mfn;
+
     uint32_t gdbsx_vcpu_event;
 
     /* A secondary copy of the vcpu time info. */