Add discard support and tests

Addresses #329.

bindings/genode/bindings.cc

@@ -402,6 +402,11 @@ struct Solo5::Platform
 		return pkt.succeeded() ? SOLO5_R_OK : SOLO5_R_EUNSPEC;
 	}
 
+    solo5_result_t block_discard(solo5_off_t, offset, size_t size)
+    {
+        return SOLO5_R_EOPNOTSUPP;
+    }
+
 	solo5_result_t block_read(solo5_off_t offset, uint8_t *buf, size_t size)
 	{
 		if ((offset|size) % blk_size)

bindings/genode/stubs.c

@@ -14,6 +14,7 @@ solo5_result_t solo5_net_read(uint8_t *buf, size_t size, size_t *read_size) { re
 
 void solo5_block_info(struct solo5_block_info *info) { }
 solo5_result_t solo5_block_write(solo5_off_t offset, const uint8_t *buf, size_t size) { return SOLO5_R_EUNSPEC; }
+solo5_result_t solo5_block_discard(solo5_off_t offset, size_t size) { return SOLO5_R_EUNSPEC; }
 solo5_result_t solo5_block_read(solo5_off_t offset, uint8_t *buf, size_t size) { return SOLO5_R_EUNSPEC; }
 
 uintptr_t __stack_chk_guard;

bindings/hvt/block.c

@@ -90,6 +90,28 @@ solo5_result_t solo5_block_read(solo5_off_t offset, uint8_t *buf, size_t size)
     return (rd.ret == 0 && rd.len == size) ? SOLO5_R_OK : SOLO5_R_EUNSPEC;
 }
 
+solo5_result_t solo5_block_discard(solo5_off_t offset, size_t size)
+{
+    if (!block_info.capacity)
+        init_block_info();
+
+    if ((offset % block_info.block_size != 0) ||
+        (size % block_info.block_size != 0) ||
+        (offset >= block_info.capacity) ||
+        (offset + size < offset) || /* checks for overflow */
+        (offset + size > block_info.capacity))
+        return SOLO5_R_EINVAL;
+
+    volatile struct hvt_blkdiscard di;
+    di.sector = offset / block_info.block_size;
+    di.len_sectors = size / block_info.block_size;
+    di.ret = 0;
+
+    hvt_do_hypercall(HVT_HYPERCALL_BLKDISCARD, &di);
+
+    return (di.ret == 0) ? SOLO5_R_OK : (di.ret == -2) ? SOLO5_R_EOPNOTSUPP : SOLO5_R_EUNSPEC;
+}
+
 void solo5_block_info(struct solo5_block_info *info)
 {
     if (!block_info.capacity)

bindings/spt/bindings.h

@@ -38,6 +38,11 @@ long sys_write(long fd, const void *buf, long size);
 long sys_pread64(long fd, void *buf, long size, long pos);
 long sys_pwrite64(long fd, const void *buf, long size, long pos);
 
+#define FALLOC_FL_KEEP_SIZE     0x01 /* default is extend size */
+#define FALLOC_FL_PUNCH_HOLE    0x02 /* de-allocates range */
+
+long sys_fallocate(long fd, long mode, long size, long pos);
+
 void sys_exit_group(long status) __attribute__((noreturn));
 
 struct sys_timespec {
@@ -59,6 +64,7 @@ struct sys_pollfd {
 #define SYS_POLLIN 1
 #define SYS_EINTR -4
 #define SYS_EAGAIN -11
+#define SYS_EOPNOTSUPP -95
 
 long sys_ppoll(void *fds, long nfds, void *ts);
 

bindings/spt/block.c

@@ -63,6 +63,27 @@ solo5_result_t solo5_block_read(solo5_off_t offset, uint8_t *buf, size_t size)
     return (nbytes == (int)size) ? SOLO5_R_OK : SOLO5_R_EUNSPEC;
 }
 
+solo5_result_t solo5_block_discard(solo5_off_t offset, size_t size) {
+    if(size % block_size != 0)
+        return SOLO5_R_EINVAL;
+    if(offset % block_size != 0)
+        return SOLO5_R_EINVAL;
+    if(offset + size < offset)
+        return SOLO5_R_EINVAL;
+    if(offset >= block_capacity)
+        return SOLO5_R_EINVAL;
+    if(offset + size > block_capacity)
+        return SOLO5_R_EINVAL;
+
+    if(size == 0)
+	    return SOLO5_R_OK;
+
+    int rv = sys_fallocate(block_fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, offset, size);
+    if(rv == SYS_EOPNOTSUPP)
+	    return SOLO5_R_EOPNOTSUPP;
+    return rv == 0 ? SOLO5_R_OK : SOLO5_R_EUNSPEC;
+}
+
 solo5_result_t solo5_block_write(solo5_off_t offset, const uint8_t *buf,
         size_t size)
 {

bindings/spt/sys_linux_aarch64.c

@@ -30,6 +30,7 @@
  * also consider explicitly inlining these functions.
  */
 
+#define SYS_fallocate     47
 #define SYS_read          63
 #define SYS_write         64
 #define SYS_pread64       67
@@ -108,6 +109,24 @@ long sys_pwrite64(long fd, const void *buf, long size, long pos)
     return x0;
 }
 
+long sys_fallocate(long fd, long mode, long size, long pos)
+{
+    register long x8 __asm__("x8") = SYS_fallocate;
+    register long x0 __asm__("x0") = fd;
+    register long x1 __asm__("x1") = mode;
+    register long x2 __asm__("x2") = size;
+    register long x3 __asm__("x3") = pos;
+
+    __asm__ __volatile__ (
+            "svc 0"
+            : "=r" (x0)
+            : "r" (x8), "r" (x0), "r" (x1), "r" (x2), "r" (x3)
+            : "memory", "cc"
+    );
+
+    return x0;
+}
+
 void sys_exit_group(long status)
 {
     register long x8 __asm__("x8") = SYS_exit_group;

bindings/spt/sys_linux_x86_64.c

@@ -37,6 +37,7 @@
 #define SYS_clock_gettime 228
 #define SYS_exit_group    231
 #define SYS_ppoll         271
+#define SYS_fallocate     285
 
 long sys_read(long fd, void *buf, long size)
 {
@@ -96,6 +97,21 @@ long sys_pwrite64(long fd, const void *buf, long size, long pos)
     return ret;
 }
 
+long sys_fallocate(long fd, long mode, long size, long pos)
+{
+    long ret;
+    register long r10 asm("r10") = pos;
+
+    __asm__ __volatile__ (
+            "syscall"
+            : "=a" (ret)
+            : "a" (SYS_fallocate), "D" (fd), "S" (mode), "d" (size), "r" (r10)
+            : "rcx", "r11", "memory"
+    );
+
+    return ret;
+}
+
 void sys_exit_group(long status)
 {
     __asm__ __volatile__ (

bindings/virtio/virtio_blk.c

@@ -30,13 +30,19 @@
 #define VIRTIO_BLK_T_FLUSH        4
 #define VIRTIO_BLK_T_FLUSH_OUT    5
 #define VIRTIO_BLK_T_GET_ID       8
+#define VIRTIO_BLK_T_DISCARD      11
+#define VIRTIO_BLK_T_WRITE_ZEROES 13
 #define VIRTIO_BLK_T_BARRIER      0x80000000
 
 #define VIRTIO_BLK_S_OK     0
 #define VIRTIO_BLK_S_IOERR  1
 #define VIRTIO_BLK_S_UNSUPP 2
 
+#define VIRTIO_BLK_F_DISCARD 13
+#define VIRTIO_BLK_F_WRITE_ZEROES 14
+
 static uint64_t virtio_blk_sectors;
+static uint32_t guest_features;
 
 #define VIRTIO_BLK_SECTOR_SIZE    512
 
@@ -147,18 +153,19 @@ static int virtio_blk_op_sync(uint32_t type,
 void virtio_config_block(struct pci_config_info *pci)
 {
     uint8_t ready_for_init = VIRTIO_PCI_STATUS_ACK | VIRTIO_PCI_STATUS_DRIVER;
-    uint32_t host_features, guest_features;
+    uint32_t host_features;
     size_t pgs;
 
     outb(pci->base + VIRTIO_PCI_STATUS, ready_for_init);
 
     host_features = inl(pci->base + VIRTIO_PCI_HOST_FEATURES);
 
-    /* don't negotiate anything for now */
-    guest_features = 0;
+    /* negociate enough for discard */
+    guest_features = host_features & (VIRTIO_BLK_F_DISCARD | VIRTIO_BLK_F_WRITE_ZEROES);
     outl(pci->base + VIRTIO_PCI_GUEST_FEATURES, guest_features);
 
     virtio_blk_sectors = inq(pci->base + VIRTIO_PCI_CONFIG_OFF);
+
     log(INFO, "Solo5: PCI:%02x:%02x: configured, capacity=%llu sectors, "
         "features=0x%x\n",
         pci->bus, pci->dev, (unsigned long long)virtio_blk_sectors,
@@ -209,6 +216,26 @@ solo5_result_t solo5_block_write(solo5_off_t offset, const uint8_t *buf,
     return (rv == 0) ? SOLO5_R_OK : SOLO5_R_EUNSPEC;
 }
 
+solo5_result_t solo5_block_discard(solo5_off_t offset, size_t size)
+{
+    assert(blk_configured);
+
+    uint64_t sector = offset / VIRTIO_BLK_SECTOR_SIZE;
+    uint64_t size_sectors = size / VIRTIO_BLK_SECTOR_SIZE;
+    if ((offset % VIRTIO_BLK_SECTOR_SIZE != 0) ||
+        (size % VIRTIO_BLK_SECTOR_SIZE != 0) ||
+        (sector >= virtio_blk_sectors) ||
+        (sector + size_sectors < sector) ||
+        (sector + size_sectors > virtio_blk_sectors))
+        return SOLO5_R_EINVAL;
+
+    if (! (guest_features & VIRTIO_BLK_F_WRITE_ZEROES))
+    {
+        return SOLO5_R_EOPNOTSUPP;
+    }
+    return SOLO5_R_EOPNOTSUPP;
+}
+
 solo5_result_t solo5_block_read(solo5_off_t offset, uint8_t *buf, size_t size)
 {
     assert(blk_configured);

include/solo5/hvt_abi.h

@@ -170,6 +170,7 @@ enum hvt_hypercall {
     HVT_HYPERCALL_NETWRITE,
     HVT_HYPERCALL_NETREAD,
     HVT_HYPERCALL_HALT,
+    HVT_HYPERCALL_BLKDISCARD,
     HVT_HYPERCALL_MAX
 };
 
@@ -284,4 +285,15 @@ struct hvt_halt {
     int exit_status;
 };
 
+struct hvt_blkdiscard {
+    /* IN */
+    size_t sector;
+
+    /* IN */
+    size_t len_sectors;
+
+    /* OUT */
+    int ret;
+};
+
 #endif /* HVT_GUEST_H */

tenders/hvt/hvt_module_blk.c

@@ -25,6 +25,7 @@
 #define _GNU_SOURCE
 #include <assert.h>
 #include <err.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
 #include <stdio.h>
@@ -72,6 +73,39 @@ static void hypercall_blkwrite(struct hvt *hvt, hvt_gpa_t gpa)
     wr->ret = 0;
 }
 
+static void hypercall_blkdiscard(struct hvt *hvt, hvt_gpa_t gpa)
+{
+    struct hvt_blkdiscard *di =
+        HVT_CHECKED_GPA_P(hvt, gpa, sizeof (struct hvt_blkdiscard));
+    ssize_t ret;
+    off_t pos, len, end;
+
+    if (di->sector >= blkinfo.num_sectors) {
+        di->ret = -1;
+        return;
+    }
+    pos = (off_t)blkinfo.sector_size * (off_t)di->sector;
+    len = (off_t)blkinfo.sector_size * (off_t)di->len_sectors;
+    if (add_overflow(pos, len, end)
+            || (end > blkinfo.num_sectors * blkinfo.sector_size))
+    {
+        di->ret = -1;
+        return;
+    }
+
+    ret = fallocate(
+            diskfd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, pos, len);
+    if (ret != 0)
+    {
+	    if (ret == -1 && errno == EOPNOTSUPP)
+            di->ret = -2;
+        else
+            di->ret = -1;
+    } else {
+        di->ret = 0;
+    }
+}
+
 static void hypercall_blkread(struct hvt *hvt, hvt_gpa_t gpa)
 {
     struct hvt_blkread *rd =
@@ -126,6 +160,8 @@ static int setup(struct hvt *hvt)
                 hypercall_blkwrite) == 0);
     assert(hvt_core_register_hypercall(HVT_HYPERCALL_BLKREAD,
                 hypercall_blkread) == 0);
+    assert(hvt_core_register_hypercall(HVT_HYPERCALL_BLKDISCARD,
+                hypercall_blkdiscard) == 0);
 
     return 0;
 }

tenders/spt/spt_module_block.c

@@ -96,6 +96,15 @@ static int setup(struct spt *spt)
     if (rc != 0)
         errx(1, "seccomp_rule_add(pwrite64, fd=%d) failed: %s", diskfd,
                 strerror(-rc));
+    rc = seccomp_rule_add(spt->sc_ctx, SCMP_ACT_ALLOW, SCMP_SYS(fallocate), 3,
+            SCMP_A0(SCMP_CMP_EQ, diskfd),
+            SCMP_A1(SCMP_CMP_EQ, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE),
+            SCMP_A2(SCMP_CMP_LE,
+                (spt->bi->blocki.capacity - spt->bi->blocki.block_size)),
+            SCMP_A3(SCMP_CMP_GE, spt->bi->blocki.block_size));
+    if (rc != 0)
+        errx(1, "seccomp_rule_add(fallocate, fd=%d) failed: %s", diskfd,
+                strerror(-rc));
 
     return 0;
 }