[Xen-changelog] [xen master] xen/domctl: Drop vcpu_alloc_lock

[patchbot@xxxxxxx]

commit 340ac8a94ab307a7d5d7a894c36d3393e66382eb
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Feb 27 17:22:40 2018 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Sep 6 16:35:59 2018 +0100

    xen/domctl: Drop vcpu_alloc_lock
    
    Since its introduction in c/s 8cbb5278e "x86/AMD: Add support for AMD's OSVW
    feature in guests", the OSVW data has been corrected to be per-domain rather
    than per-vcpu, and is initialised during XEN_DOMCTL_createdomain.
    
    Furthermore, because XENPF_microcode_update uses hypercall continuations to
    move between CPUs, it drops the vcpu_alloc_lock mid update, meaning that it
    didn't provided the interlock guarantee that the OSVW patch was looking for 
in
    the first place.
    
    This interlock serves no purpose, so take the opportunity to drop it and
    remove a global spinlock from the hypervisor.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/arch/x86/platform_hypercall.c | 15 ---------------
 xen/common/domctl.c               | 18 ------------------
 xen/include/xen/domain.h          |  1 -
 3 files changed, 34 deletions(-)

diff --git a/xen/arch/x86/platform_hypercall.c 
b/xen/arch/x86/platform_hypercall.c
index ea18c3215a..b19f6ec4ed 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -280,24 +280,9 @@ ret_t 
do_platform_op(XEN_GUEST_HANDLE_PARAM(xen_platform_op_t) u_xenpf_op)
 
         guest_from_compat_handle(data, op->u.microcode.data);
 
-        /*
-         * alloc_vcpu() will access data which is modified during
-         * microcode update
-         */
-        while ( !spin_trylock(&vcpu_alloc_lock) )
-        {
-            if ( hypercall_preempt_check() )
-            {
-                ret = hypercall_create_continuation(
-                    __HYPERVISOR_platform_op, "h", u_xenpf_op);
-                goto out;
-            }
-        }
-
         ret = microcode_update(
                 guest_handle_to_param(data, const_void),
                 op->u.microcode.length);
-        spin_unlock(&vcpu_alloc_lock);
     }
     break;
 
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index ee0983d2db..ed047b7cd7 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -34,7 +34,6 @@
 #include <xsm/xsm.h>
 
 static DEFINE_SPINLOCK(domctl_lock);
-DEFINE_SPINLOCK(vcpu_alloc_lock);
 
 static int bitmap_to_xenctl_bitmap(struct xenctl_bitmap *xenctl_bitmap,
                                    const unsigned long *bitmap,
@@ -560,20 +559,6 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         /* Needed, for example, to ensure writable p.t. state is synced. */
         domain_pause(d);
 
-        /*
-         * Certain operations (e.g. CPU microcode updates) modify data which is
-         * used during VCPU allocation/initialization
-         */
-        while ( !spin_trylock(&vcpu_alloc_lock) )
-        {
-            if ( hypercall_preempt_check() )
-            {
-                ret =  hypercall_create_continuation(
-                    __HYPERVISOR_domctl, "h", u_domctl);
-                goto maxvcpu_out_novcpulock;
-            }
-        }
-
         ret = -ENOMEM;
         online = cpupool_domain_cpumask(d);
 
@@ -593,9 +578,6 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         ret = 0;
 
     maxvcpu_out:
-        spin_unlock(&vcpu_alloc_lock);
-
-    maxvcpu_out_novcpulock:
         domain_unpause(d);
         break;
     }
diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
index ce31999cb7..5593495159 100644
--- a/xen/include/xen/domain.h
+++ b/xen/include/xen/domain.h
@@ -87,7 +87,6 @@ void arch_dump_domain_info(struct domain *d);
 
 int arch_vcpu_reset(struct vcpu *);
 
-extern spinlock_t vcpu_alloc_lock;
 bool_t domctl_lock_acquire(void);
 void domctl_lock_release(void);
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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