[PATCH 1/2] um: virt-pci: don't do DMA from stack
Johannes Berg
johannes at sipsolutions.net
Wed Aug 11 07:58:25 PDT 2021
From: Johannes Berg <johannes.berg at intel.com>
When enabling VMAP_STACK, SG helpers immediately complained
that we were doing DMA from stack. Use per-CPU variables to
avoid that.
Signed-off-by: Johannes Berg <johannes.berg at intel.com>
---
arch/um/drivers/virt-pci.c | 104 +++++++++++++++++++++++++++----------
1 file changed, 78 insertions(+), 26 deletions(-)
diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
index 70c17de16662..c08066633023 100644
--- a/arch/um/drivers/virt-pci.c
+++ b/arch/um/drivers/virt-pci.c
@@ -56,6 +56,13 @@ static unsigned long um_pci_msi_used[BITS_TO_LONGS(MAX_MSI_VECTORS)];
#define UM_VIRT_PCI_MAXDELAY 40000
+struct um_pci_message_buffer {
+ struct virtio_pcidev_msg hdr;
+ u8 data[8];
+};
+
+static struct um_pci_message_buffer __percpu *um_pci_msg_bufs;
+
static int um_pci_send_cmd(struct um_pci_device *dev,
struct virtio_pcidev_msg *cmd,
unsigned int cmd_size,
@@ -68,11 +75,12 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
[1] = extra ? &extra_sg : &in_sg,
[2] = extra ? &in_sg : NULL,
};
+ struct um_pci_message_buffer *buf;
int delay_count = 0;
int ret, len;
bool posted;
- if (WARN_ON(cmd_size < sizeof(*cmd)))
+ if (WARN_ON(cmd_size < sizeof(*cmd) || cmd_size > sizeof(*buf)))
return -EINVAL;
switch (cmd->op) {
@@ -88,6 +96,9 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
break;
}
+ buf = get_cpu_var(um_pci_msg_bufs);
+ memcpy(buf, cmd, cmd_size);
+
if (posted) {
u8 *ncmd = kmalloc(cmd_size + extra_size, GFP_ATOMIC);
@@ -102,7 +113,10 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
} else {
/* try without allocating memory */
posted = false;
+ cmd = (void *)buf;
}
+ } else {
+ cmd = (void *)buf;
}
sg_init_one(&out_sg, cmd, cmd_size);
@@ -118,11 +132,12 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
posted ? cmd : HANDLE_NO_FREE(cmd),
GFP_ATOMIC);
if (ret)
- return ret;
+ goto out;
if (posted) {
virtqueue_kick(dev->cmd_vq);
- return 0;
+ ret = 0;
+ goto out;
}
/* kick and poll for getting a response on the queue */
@@ -148,6 +163,8 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
}
clear_bit(UM_PCI_STAT_WAITING, &dev->status);
+out:
+ put_cpu_var(um_pci_msg_bufs);
return ret;
}
@@ -161,12 +178,17 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
.size = size,
.addr = offset,
};
- /* maximum size - we may only use parts of it */
- u8 data[8];
+ /* buf->data is maximum size - we may only use parts of it */
+ struct um_pci_message_buffer *buf;
+ u8 *data;
+ unsigned long ret = ~0ULL;
if (!dev)
return ~0ULL;
+ buf = get_cpu_var(um_pci_msg_bufs);
+ data = buf->data;
+
memset(data, 0xff, sizeof(data));
switch (size) {
@@ -179,27 +201,34 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
break;
default:
WARN(1, "invalid config space read size %d\n", size);
- return ~0ULL;
+ goto out;
}
- if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0,
- data, sizeof(data)))
- return ~0ULL;
+ if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, 8))
+ goto out;
switch (size) {
case 1:
- return data[0];
+ ret = data[0];
+ break;
case 2:
- return le16_to_cpup((void *)data);
+ ret = le16_to_cpup((void *)data);
+ break;
case 4:
- return le32_to_cpup((void *)data);
+ ret = le32_to_cpup((void *)data);
+ break;
#ifdef CONFIG_64BIT
case 8:
- return le64_to_cpup((void *)data);
+ ret = le64_to_cpup((void *)data);
+ break;
#endif
default:
- return ~0ULL;
+ break;
}
+
+out:
+ put_cpu_var(um_pci_msg_bufs);
+ return ret;
}
static void um_pci_cfgspace_write(void *priv, unsigned int offset, int size,
@@ -272,8 +301,13 @@ static void um_pci_bar_copy_from(void *priv, void *buffer,
static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
int size)
{
- /* maximum size - we may only use parts of it */
- u8 data[8];
+ /* buf->data is maximum size - we may only use parts of it */
+ struct um_pci_message_buffer *buf;
+ u8 *data;
+ unsigned long ret = ~0ULL;
+
+ buf = get_cpu_var(um_pci_msg_bufs);
+ data = buf->data;
switch (size) {
case 1:
@@ -285,25 +319,33 @@ static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
break;
default:
WARN(1, "invalid config space read size %d\n", size);
- return ~0ULL;
+ goto out;
}
um_pci_bar_copy_from(priv, data, offset, size);
switch (size) {
case 1:
- return data[0];
+ ret = data[0];
+ break;
case 2:
- return le16_to_cpup((void *)data);
+ ret = le16_to_cpup((void *)data);
+ break;
case 4:
- return le32_to_cpup((void *)data);
+ ret = le32_to_cpup((void *)data);
+ break;
#ifdef CONFIG_64BIT
case 8:
- return le64_to_cpup((void *)data);
+ ret = le64_to_cpup((void *)data);
+ break;
#endif
default:
- return ~0ULL;
+ break;
}
+
+out:
+ put_cpu_var(um_pci_msg_bufs);
+ return ret;
}
static void um_pci_bar_copy_to(void *priv, unsigned int offset,
@@ -823,10 +865,16 @@ static int um_pci_init(void)
"No virtio device ID configured for PCI - no PCI support\n"))
return 0;
- bridge = pci_alloc_host_bridge(0);
- if (!bridge)
+ um_pci_msg_bufs = alloc_percpu(struct um_pci_message_buffer);
+ if (!um_pci_msg_bufs)
return -ENOMEM;
+ bridge = pci_alloc_host_bridge(0);
+ if (!bridge) {
+ err = -ENOMEM;
+ goto free;
+ }
+
um_pci_fwnode = irq_domain_alloc_named_fwnode("um-pci");
if (!um_pci_fwnode) {
err = -ENOMEM;
@@ -878,8 +926,11 @@ static int um_pci_init(void)
irq_domain_remove(um_pci_inner_domain);
if (um_pci_fwnode)
irq_domain_free_fwnode(um_pci_fwnode);
- pci_free_resource_list(&bridge->windows);
- pci_free_host_bridge(bridge);
+ if (bridge) {
+ pci_free_resource_list(&bridge->windows);
+ pci_free_host_bridge(bridge);
+ }
+ free_percpu(um_pci_msg_bufs);
return err;
}
module_init(um_pci_init);
@@ -891,5 +942,6 @@ static void um_pci_exit(void)
irq_domain_remove(um_pci_inner_domain);
pci_free_resource_list(&bridge->windows);
pci_free_host_bridge(bridge);
+ free_percpu(um_pci_msg_bufs);
}
module_exit(um_pci_exit);
--
2.31.1
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