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Re: [Qemu-devel] [PATCH v2] bugfix: passing reference instead of value
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v2] bugfix: passing reference instead of value |
Date: |
Tue, 29 Dec 2015 17:25:38 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 |
>>> Separated from previous "igd-passthru convert to realize" patch. Since
>>> these two don`t have dependency, can send it solely.
>>>
>>> Not test since it is easy to find out if reading carefully, just
>>> compiled.
This patch works but the added conversion to LE is conceptually wrong.
The conversion from LE to CPU and vice versa is already done by
host_pci_config_read and pci_default_write_config. You don't have it in
host_pci_config_read because the code is not portable and x86 is
little-endian.
Generally, functions that accept/return integers take care themselves of
endianness conversions.
Paolo
>>> hw/pci-host/piix.c | 10 ++++++----
>>> 1 file changed, 6 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
>>> index 715208b..a9cb983 100644
>>> --- a/hw/pci-host/piix.c
>>> +++ b/hw/pci-host/piix.c
>>> @@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
>>> {0xa8, 4}, /* SNB: base of GTT stolen memory */
>>> };
>>>
>>> -static int host_pci_config_read(int pos, int len, uint32_t val)
>>> +static int host_pci_config_read(int pos, int len, uint32_t *val)
>>> {
>>> char path[PATH_MAX];
>>> int config_fd;
>>> @@ -784,12 +784,14 @@ static int host_pci_config_read(int pos, int
>>> len, uint32_t val)
>>> ret = -errno;
>>> goto out;
>>> }
>>> +
>>> do {
>>> - rc = read(config_fd, (uint8_t *)&val, len);
>>> + rc = read(config_fd, (uint8_t *)val, len);
>>> } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
>>> if (rc != len) {
>>> ret = -errno;
>>> }
>>> +
>>> out:
>>> close(config_fd);
>>> return ret;
>>> @@ -805,11 +807,11 @@ static int igd_pt_i440fx_initfn(struct PCIDevice
>>> *pci_dev)
>>> for (i = 0; i < num; i++) {
>>> pos = igd_host_bridge_infos[i].offset;
>>> len = igd_host_bridge_infos[i].len;
>>> - rc = host_pci_config_read(pos, len, val);
>>> + rc = host_pci_config_read(pos, len, &val);
>>> if (rc) {
>>> return -ENODEV;
>>> }
>>> - pci_default_write_config(pci_dev, pos, val, len);
>>> + pci_default_write_config(pci_dev, pos, cpu_to_le32(val), len);
>>> }
>>>
>>> return 0;
>>>
>>
>