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Subject[PATCH] xen: don't use privcmd_call() from xen_mc_flush()
Date
Using privcmd_call() for a singleton multicall seems to be wrong, as
privcmd_call() is using stac()/clac() to enable hypervisor access to
Linux user space.

Add a new xen_single_call() function to be use for that purpose.

Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
arch/x86/include/asm/xen/hypercall.h | 25 +++++++++++++++++++------
arch/x86/xen/multicalls.c | 6 +++---
2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index bfd882617613..6b2f90a0b149 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -209,24 +209,37 @@ extern struct { char _entry[32]; } hypercall_page[];
})

static inline long
-privcmd_call(unsigned call,
- unsigned long a1, unsigned long a2,
- unsigned long a3, unsigned long a4,
- unsigned long a5)
+xen_single_call(unsigned int call,
+ unsigned long a1, unsigned long a2,
+ unsigned long a3, unsigned long a4,
+ unsigned long a5)
{
__HYPERCALL_DECLS;
__HYPERCALL_5ARG(a1, a2, a3, a4, a5);

- stac();
asm volatile(CALL_NOSPEC
: __HYPERCALL_5PARAM
: [thunk_target] "a" (&hypercall_page[call])
: __HYPERCALL_CLOBBER5);
- clac();

return (long)__res;
}

+static inline long
+privcmd_call(unsigned int call,
+ unsigned long a1, unsigned long a2,
+ unsigned long a3, unsigned long a4,
+ unsigned long a5)
+{
+ long res;
+
+ stac();
+ res = xen_single_call(call, a1, a2, a3, a4, a5);
+ clac();
+
+ return res;
+}
+
static inline int
HYPERVISOR_set_trap_table(struct trap_info *table)
{
diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
index dc502ca8263e..2bce7958ce8b 100644
--- a/arch/x86/xen/multicalls.c
+++ b/arch/x86/xen/multicalls.c
@@ -80,9 +80,9 @@ void xen_mc_flush(void)
and just do the call directly. */
mc = &b->entries[0];

- mc->result = privcmd_call(mc->op,
- mc->args[0], mc->args[1], mc->args[2],
- mc->args[3], mc->args[4]);
+ mc->result = xen_single_call(mc->op, mc->args[0], mc->args[1],
+ mc->args[2], mc->args[3],
+ mc->args[4]);
ret = mc->result < 0;
break;

--
2.13.7
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