[Xen-devel] [PATCH 1/7] x86/xen: Simplify set_aliased_prot

[Andy Lutomirski <luto@xxxxxxxxxx>]

In aa1acff356bb ("x86/xen: Probe target addresses in
set_aliased_prot() before the hypercall"), I added an explicit probe
to work around a hypercall issue.  The code can be simplified by
using probe_kernel_read.

Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <dvrabel@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: xen-devel <xen-devel@xxxxxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
 arch/x86/xen/enlighten.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 6ab672233ac9..eed696c229ba 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -521,9 +521,7 @@ static void set_aliased_prot(void *v, pgprot_t prot)
 
        preempt_disable();
 
-       pagefault_disable();    /* Avoid warnings due to being atomic. */
-       __get_user(dummy, (unsigned char __user __force *)v);
-       pagefault_enable();
+       probe_kernel_read(&dummy, (unsigned char *)v, 1);
 
        if (HYPERVISOR_update_va_mapping((unsigned long)v, pte, 0))
                BUG();
-- 
2.5.5


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