Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 355 insertions, 0 deletions

diff --git a/util/bufferiszero.c b/util/bufferiszero.c
new file mode 100644
index 000000000..695bb4ce2
--- /dev/null
+++ b/util/bufferiszero.c
@@ -0,0 +1,355 @@
+/*
+ * Simple C functions to supplement the C library
+ *
+ * Copyright (c) 2006 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu/osdep.h"
+#include "qemu/cutils.h"
+#include "qemu/bswap.h"
+
+static bool
+buffer_zero_int(const void *buf, size_t len)
+{
+    if (unlikely(len < 8)) {
+        /* For a very small buffer, simply accumulate all the bytes.  */
+        const unsigned char *p = buf;
+        const unsigned char *e = buf + len;
+        unsigned char t = 0;
+
+        do {
+            t |= *p++;
+        } while (p < e);
+
+        return t == 0;
+    } else {
+        /* Otherwise, use the unaligned memory access functions to
+           handle the beginning and end of the buffer, with a couple
+           of loops handling the middle aligned section.  */
+        uint64_t t = ldq_he_p(buf);
+        const uint64_t *p = (uint64_t *)(((uintptr_t)buf + 8) & -8);
+        const uint64_t *e = (uint64_t *)(((uintptr_t)buf + len) & -8);
+
+        for (; p + 8 <= e; p += 8) {
+            __builtin_prefetch(p + 8);
+            if (t) {
+                return false;
+            }
+            t = p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7];
+        }
+        while (p < e) {
+            t |= *p++;
+        }
+        t |= ldq_he_p(buf + len - 8);
+
+        return t == 0;
+    }
+}
+
+#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
+/* Do not use push_options pragmas unnecessarily, because clang
+ * does not support them.
+ */
+#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
+#pragma GCC push_options
+#pragma GCC target("sse2")
+#endif
+#include <emmintrin.h>
+
+/* Note that each of these vectorized functions require len >= 64.  */
+
+static bool
+buffer_zero_sse2(const void *buf, size_t len)
+{
+    __m128i t = _mm_loadu_si128(buf);
+    __m128i *p = (__m128i *)(((uintptr_t)buf + 5 * 16) & -16);
+    __m128i *e = (__m128i *)(((uintptr_t)buf + len) & -16);
+    __m128i zero = _mm_setzero_si128();
+
+    /* Loop over 16-byte aligned blocks of 64.  */
+    while (likely(p <= e)) {
+        __builtin_prefetch(p);
+        t = _mm_cmpeq_epi8(t, zero);
+        if (unlikely(_mm_movemask_epi8(t) != 0xFFFF)) {
+            return false;
+        }
+        t = p[-4] | p[-3] | p[-2] | p[-1];
+        p += 4;
+    }
+
+    /* Finish the aligned tail.  */
+    t |= e[-3];
+    t |= e[-2];
+    t |= e[-1];
+
+    /* Finish the unaligned tail.  */
+    t |= _mm_loadu_si128(buf + len - 16);
+
+    return _mm_movemask_epi8(_mm_cmpeq_epi8(t, zero)) == 0xFFFF;
+}
+#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
+#pragma GCC pop_options
+#endif
+
+#ifdef CONFIG_AVX2_OPT
+/* Note that due to restrictions/bugs wrt __builtin functions in gcc <= 4.8,
+ * the includes have to be within the corresponding push_options region, and
+ * therefore the regions themselves have to be ordered with increasing ISA.
+ */
+#pragma GCC push_options
+#pragma GCC target("sse4")
+#include <smmintrin.h>
+
+static bool
+buffer_zero_sse4(const void *buf, size_t len)
+{
+    __m128i t = _mm_loadu_si128(buf);
+    __m128i *p = (__m128i *)(((uintptr_t)buf + 5 * 16) & -16);
+    __m128i *e = (__m128i *)(((uintptr_t)buf + len) & -16);
+
+    /* Loop over 16-byte aligned blocks of 64.  */
+    while (likely(p <= e)) {
+        __builtin_prefetch(p);
+        if (unlikely(!_mm_testz_si128(t, t))) {
+            return false;
+        }
+        t = p[-4] | p[-3] | p[-2] | p[-1];
+        p += 4;
+    }
+
+    /* Finish the aligned tail.  */
+    t |= e[-3];
+    t |= e[-2];
+    t |= e[-1];
+
+    /* Finish the unaligned tail.  */
+    t |= _mm_loadu_si128(buf + len - 16);
+
+    return _mm_testz_si128(t, t);
+}
+
+#pragma GCC pop_options
+#pragma GCC push_options
+#pragma GCC target("avx2")
+#include <immintrin.h>
+
+static bool
+buffer_zero_avx2(const void *buf, size_t len)
+{
+    /* Begin with an unaligned head of 32 bytes.  */
+    __m256i t = _mm256_loadu_si256(buf);
+    __m256i *p = (__m256i *)(((uintptr_t)buf + 5 * 32) & -32);
+    __m256i *e = (__m256i *)(((uintptr_t)buf + len) & -32);
+
+    /* Loop over 32-byte aligned blocks of 128.  */
+    while (p <= e) {
+        __builtin_prefetch(p);
+        if (unlikely(!_mm256_testz_si256(t, t))) {
+            return false;
+        }
+        t = p[-4] | p[-3] | p[-2] | p[-1];
+        p += 4;
+    } ;
+
+    /* Finish the last block of 128 unaligned.  */
+    t |= _mm256_loadu_si256(buf + len - 4 * 32);
+    t |= _mm256_loadu_si256(buf + len - 3 * 32);
+    t |= _mm256_loadu_si256(buf + len - 2 * 32);
+    t |= _mm256_loadu_si256(buf + len - 1 * 32);
+
+    return _mm256_testz_si256(t, t);
+}
+#pragma GCC pop_options
+#endif /* CONFIG_AVX2_OPT */
+
+#ifdef CONFIG_AVX512F_OPT
+#pragma GCC push_options
+#pragma GCC target("avx512f")
+#include <immintrin.h>
+
+static bool
+buffer_zero_avx512(const void *buf, size_t len)
+{
+    /* Begin with an unaligned head of 64 bytes.  */
+    __m512i t = _mm512_loadu_si512(buf);
+    __m512i *p = (__m512i *)(((uintptr_t)buf + 5 * 64) & -64);
+    __m512i *e = (__m512i *)(((uintptr_t)buf + len) & -64);
+
+    /* Loop over 64-byte aligned blocks of 256.  */
+    while (p <= e) {
+        __builtin_prefetch(p);
+        if (unlikely(_mm512_test_epi64_mask(t, t))) {
+            return false;
+        }
+        t = p[-4] | p[-3] | p[-2] | p[-1];
+        p += 4;
+    }
+
+    t |= _mm512_loadu_si512(buf + len - 4 * 64);
+    t |= _mm512_loadu_si512(buf + len - 3 * 64);
+    t |= _mm512_loadu_si512(buf + len - 2 * 64);
+    t |= _mm512_loadu_si512(buf + len - 1 * 64);
+
+    return !_mm512_test_epi64_mask(t, t);
+
+}
+#pragma GCC pop_options
+#endif
+
+
+/* Note that for test_buffer_is_zero_next_accel, the most preferred
+ * ISA must have the least significant bit.
+ */
+#define CACHE_AVX512F 1
+#define CACHE_AVX2    2
+#define CACHE_SSE4    4
+#define CACHE_SSE2    8
+
+/* Make sure that these variables are appropriately initialized when
+ * SSE2 is enabled on the compiler command-line, but the compiler is
+ * too old to support CONFIG_AVX2_OPT.
+ */
+#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
+# define INIT_CACHE 0
+# define INIT_ACCEL buffer_zero_int
+#else
+# ifndef __SSE2__
+#  error "ISA selection confusion"
+# endif
+# define INIT_CACHE CACHE_SSE2
+# define INIT_ACCEL buffer_zero_sse2
+#endif
+
+static unsigned cpuid_cache = INIT_CACHE;
+static bool (*buffer_accel)(const void *, size_t) = INIT_ACCEL;
+static int length_to_accel = 64;
+
+static void init_accel(unsigned cache)
+{
+    bool (*fn)(const void *, size_t) = buffer_zero_int;
+    if (cache & CACHE_SSE2) {
+        fn = buffer_zero_sse2;
+        length_to_accel = 64;
+    }
+#ifdef CONFIG_AVX2_OPT
+    if (cache & CACHE_SSE4) {
+        fn = buffer_zero_sse4;
+        length_to_accel = 64;
+    }
+    if (cache & CACHE_AVX2) {
+        fn = buffer_zero_avx2;
+        length_to_accel = 128;
+    }
+#endif
+#ifdef CONFIG_AVX512F_OPT
+    if (cache & CACHE_AVX512F) {
+        fn = buffer_zero_avx512;
+        length_to_accel = 256;
+    }
+#endif
+    buffer_accel = fn;
+}
+
+#if defined(CONFIG_AVX512F_OPT) || defined(CONFIG_AVX2_OPT)
+#include "qemu/cpuid.h"
+
+static void __attribute__((constructor)) init_cpuid_cache(void)
+{
+    int max = __get_cpuid_max(0, NULL);
+    int a, b, c, d;
+    unsigned cache = 0;
+
+    if (max >= 1) {
+        __cpuid(1, a, b, c, d);
+        if (d & bit_SSE2) {
+            cache |= CACHE_SSE2;
+        }
+        if (c & bit_SSE4_1) {
+            cache |= CACHE_SSE4;
+        }
+
+        /* We must check that AVX is not just available, but usable.  */
+        if ((c & bit_OSXSAVE) && (c & bit_AVX) && max >= 7) {
+            int bv;
+            __asm("xgetbv" : "=a"(bv), "=d"(d) : "c"(0));
+            __cpuid_count(7, 0, a, b, c, d);
+            if ((bv & 0x6) == 0x6 && (b & bit_AVX2)) {
+                cache |= CACHE_AVX2;
+            }
+            /* 0xe6:
+            *  XCR0[7:5] = 111b (OPMASK state, upper 256-bit of ZMM0-ZMM15
+            *                    and ZMM16-ZMM31 state are enabled by OS)
+            *  XCR0[2:1] = 11b (XMM state and YMM state are enabled by OS)
+            */
+            if ((bv & 0xe6) == 0xe6 && (b & bit_AVX512F)) {
+                cache |= CACHE_AVX512F;
+            }
+        }
+    }
+    cpuid_cache = cache;
+    init_accel(cache);
+}
+#endif /* CONFIG_AVX2_OPT */
+
+bool test_buffer_is_zero_next_accel(void)
+{
+    /* If no bits set, we just tested buffer_zero_int, and there
+       are no more acceleration options to test.  */
+    if (cpuid_cache == 0) {
+        return false;
+    }
+    /* Disable the accelerator we used before and select a new one.  */
+    cpuid_cache &= cpuid_cache - 1;
+    init_accel(cpuid_cache);
+    return true;
+}
+
+static bool select_accel_fn(const void *buf, size_t len)
+{
+    if (likely(len >= length_to_accel)) {
+        return buffer_accel(buf, len);
+    }
+    return buffer_zero_int(buf, len);
+}
+
+#else
+#define select_accel_fn  buffer_zero_int
+bool test_buffer_is_zero_next_accel(void)
+{
+    return false;
+}
+#endif
+
+/*
+ * Checks if a buffer is all zeroes
+ */
+bool buffer_is_zero(const void *buf, size_t len)
+{
+    if (unlikely(len == 0)) {
+        return true;
+    }
+
+    /* Fetch the beginning of the buffer while we select the accelerator.  */
+    __builtin_prefetch(buf);
+
+    /* Use an optimized zero check if possible.  Note that this also
+       includes a check for an unrolled loop over 64-bit integers.  */
+    return select_accel_fn(buf, len);
+}