linux-kernel - Re: [PATCH net-next 0/3] vhost: accelerate metadata access through vmap()

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Date:   Fri, 14 Dec 2018 10:31:28 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 0/3] vhost: accelerate metadata access through
 vmap()

On Fri, Dec 14, 2018 at 07:33:20AM -0500, Michael S. Tsirkin wrote:
> > - unsafe_put_user/unsafe_get_user is not sufficient for accessing structures
> > (e.g accessing descriptor) or arrays (batching).
> 
> So you want unsafe_copy_xxx_user? I can do this. Hang on will post.

Like this basically? Warning: completely untested.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>


diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index b5e58cc0c5e7..d2afd70793ca 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -728,5 +728,10 @@ do {										\
 	if (unlikely(__gu_err)) goto err_label;					\
 } while (0)
 
+#define unsafe_copy_from_user(to, from, n)					\
+	 __copy_user_ll(to, (__force const void *)from, n)
+#define unsafe_copy_to_user(to, from, n)					\
+	 __copy_user_ll((__force void *)to, from, n)
+
 #endif /* _ASM_X86_UACCESS_H */
 
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index efe79c1cdd47..b9d515ba2920 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -271,6 +271,8 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
 #define user_access_end() do { } while (0)
 #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
 #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)
+#define unsafe_copy_to_user(from, to, n) copy_to_user(from, to, n)
+#define unsafe_copy_from_user(from, to, n) copy_from_user(from, to, n)
 #endif
 
 #ifdef CONFIG_HARDENED_USERCOPY