Revert "x86/sev: Unroll string mmio with CC_ATTR_GUEST_UNROLL_STRING_IO"

BugLink: https://bugs.launchpad.net/bugs/2020319

This reverts commit a49731f. The upstream
version will be reapplied in the following commit in order to keep
cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO), instead of
sev_key_active().

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

Author: Thadeu Lima de Souza Cascardo

arch/x86/lib/iomem.c

@@ -22,7 +22,7 @@ static __always_inline void rep_movs(void *to, const void *from, size_t n)
 		     : "memory");
 }
 
-static void string_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
+void memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
 {
 	if (unlikely(!n))
 		return;
@@ -38,8 +38,9 @@ static void string_memcpy_fromio(void *to, const volatile void __iomem *from, si
 	}
 	rep_movs(to, (const void *)from, n);
 }
+EXPORT_SYMBOL(memcpy_fromio);
 
-static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
+void memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
 {
 	if (unlikely(!n))
 		return;
@@ -55,64 +56,14 @@ static void string_memcpy_toio(volatile void __iomem *to, const void *from, size
 	}
 	rep_movs((void *)to, (const void *) from, n);
 }
-
-static void unrolled_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
-{
-	const volatile char __iomem *in = from;
-	char *out = to;
-	int i;
-
-	for (i = 0; i < n; ++i)
-		out[i] = readb(&in[i]);
-}
-
-static void unrolled_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
-{
-	volatile char __iomem *out = to;
-	const char *in = from;
-	int i;
-
-	for (i = 0; i < n; ++i)
-		writeb(in[i], &out[i]);
-}
-
-static void unrolled_memset_io(volatile void __iomem *a, int b, size_t c)
-{
-	volatile char __iomem *mem = a;
-	int i;
-
-	for (i = 0; i < c; ++i)
-		writeb(b, &mem[i]);
-}
-
-void memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
-{
-	if (sev_key_active())
-		unrolled_memcpy_fromio(to, from, n);
-	else
-		string_memcpy_fromio(to, from, n);
-}
-EXPORT_SYMBOL(memcpy_fromio);
-
-void memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
-{
-	if (sev_key_active())
-		unrolled_memcpy_toio(to, from, n);
-	else
-		string_memcpy_toio(to, from, n);
-}
 EXPORT_SYMBOL(memcpy_toio);
 
 void memset_io(volatile void __iomem *a, int b, size_t c)
 {
-	if (sev_key_active()) {
-		unrolled_memset_io(a, b, c);
-	} else {
-		/*
-		 * TODO: memset can mangle the IO patterns quite a bit.
-		 * perhaps it would be better to use a dumb one:
-		 */
-		memset((void *)a, b, c);
-	}
+	/*
+	 * TODO: memset can mangle the IO patterns quite a bit.
+	 * perhaps it would be better to use a dumb one:
+	 */
+	memset((void *)a, b, c);
 }
 EXPORT_SYMBOL(memset_io);