Re: [PATCH 12/13] pci-assign: Generic config space access management

Jan Kiszka
2011-06-28T08:18:23Z

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On 2011-06-28 10:10, Michael S. Tsirkin wrote:
> On Mon, Jun 27, 2011 at 08:19:55PM +0200, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> This drastically simplifies config space access management: Instead of
>> coding various range checks and merging bits, set up two access control
>> bitmaps. One defines, which bits can be directly read from the device,
>> the other allows direct write to the device, also with bit-granularity.
>>
>> The setup of those bitmaps, specifically the corner cases like the
>> capability list status bit, is way more readable than the existing code.
>> And the generic config access functions just need one additional logic
>> to catch writes to the MSI/MSI-X control flags and call the related
>> update handlers.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>> hw/device-assignment.c | 325 ++++++++++++++++-------------------------------
>> hw/device-assignment.h | 3 +-
>> 2 files changed, 113 insertions(+), 215 deletions(-)
>>
>> diff --git a/hw/device-assignment.c b/hw/device-assignment.c
>> index 6a2ca8c..be199d2 100644
>> --- a/hw/device-assignment.c
>> +++ b/hw/device-assignment.c
>> @@ -63,35 +63,6 @@ static void assigned_dev_load_option_rom(AssignedDevice *dev);
>>
>> static void assigned_dev_unregister_msix_mmio(AssignedDevice *dev);
>>
>> -static void assigned_device_pci_cap_write_config(PCIDevice *pci_dev,
>> - uint32_t address,
>> - uint32_t val, int len);
>> -
>> -static uint32_t assigned_device_pci_cap_read_config(PCIDevice *pci_dev,
>> - uint32_t address, int len);
>> -
>> -/* Merge the bits set in mask from mval into val. Both val and mval are
>> - * at the same addr offset, pos is the starting offset of the mask. */
>> -static uint32_t merge_bits(uint32_t val, uint32_t mval, uint8_t addr,
>> - int len, uint8_t pos, uint32_t mask)
>> -{
>> - if (!ranges_overlap(addr, len, pos, 4)) {
>> - return val;
>> - }
>> -
>> - if (addr >= pos) {
>> - mask >>= (addr - pos) * 8;
>> - } else {
>> - mask <<= (pos - addr) * 8;
>> - }
>> - mask &= 0xffffffffU >> (4 - len) * 8;
>> -
>> - val &= ~mask;
>> - val |= (mval & mask);
>> -
>> - return val;
>> -}
>> -
>> static uint32_t assigned_dev_ioport_rw(AssignedDevRegion *dev_region,
>> uint32_t addr, int len, uint32_t *val)
>> {
>> @@ -404,143 +375,6 @@ static uint8_t pci_find_cap_offset(PCIDevice *d, uint8_t cap, uint8_t start)
>> return 0;
>> }
>>
>> -static void assigned_dev_pci_write_config(PCIDevice *d, uint32_t address,
>> - uint32_t val, int len)
>> -{
>> - int fd;
>> - ssize_t ret;
>> - AssignedDevice *pci_dev = DO_UPCAST(AssignedDevice, dev, d);
>> -
>> - DEBUG("(%x.%x): address=%04x val=0x%08x len=%d\n",
>> - ((d->devfn >> 3) & 0x1F), (d->devfn & 0x7),
>> - (uint16_t) address, val, len);
>> -
>> - if (address >= PCI_CONFIG_HEADER_SIZE && d->config_map[address]) {
>> - return assigned_device_pci_cap_write_config(d, address, val, len);
>> - }
>> -
>> - if (ranges_overlap(address, len, PCI_COMMAND, 2)) {
>> - pci_default_write_config(d, address, val, len);
>> - /* Continue to program the card */
>> - }
>> -
>> - /*
>> - * Catch access to
>> - * - base address registers
>> - * - ROM base address & capability pointer
>> - * - interrupt line & pin
>> - */
>> - if (ranges_overlap(address, len, PCI_BASE_ADDRESS_0, 24) ||
>> - ranges_overlap(address, len, PCI_ROM_ADDRESS, 4)) {
>> - pci_default_write_config(d, address, val, len);
>> - return;
>> - } else if (ranges_overlap(address, len, PCI_CAPABILITY_LIST, 1) ||
>> - ranges_overlap(address, len, PCI_INTERRUPT_LINE, 2)) {
>> - uint32_t real_val;
>> -
>> - pci_default_write_config(d, address, val, len);
>> -
>> - /* Ensure that writes to overlapping areas we don't virtualize still
>> - * hit the device. */
>> - real_val = assigned_dev_pci_read(d, address, len);
>> - val = merge_bits(val, real_val, address, len,
>> - PCI_CAPABILITY_LIST, 0xff);
>> - val = merge_bits(val, real_val, address, len,
>> - PCI_INTERRUPT_LINE, 0xffff);
>> - }
>> -
>> - DEBUG("NON BAR (%x.%x): address=%04x val=0x%08x len=%d\n",
>> - ((d->devfn >> 3) & 0x1F), (d->devfn & 0x7),
>> - (uint16_t) address, val, len);
>> -
>> - fd = pci_dev->real_device.config_fd;
>> -
>> -again:
>> - ret = pwrite(fd, &val, len, address);
>> - if (ret != len) {
>> - if ((ret < 0) && (errno == EINTR || errno == EAGAIN))
>> - goto again;
>> -
>> - fprintf(stderr, "%s: pwrite failed, ret = %zd errno = %d\n",
>> - __func__, ret, errno);
>> -
>> - exit(1);
>> - }
>> -}
>> -
>> -static uint32_t assigned_dev_pci_read_config(PCIDevice *d, uint32_t address,
>> - int len)
>> -{
>> - uint32_t val = 0, virt_val;
>> - int fd;
>> - ssize_t ret;
>> - AssignedDevice *pci_dev = DO_UPCAST(AssignedDevice, dev, d);
>> -
>> - if (address >= PCI_CONFIG_HEADER_SIZE && d->config_map[address]) {
>> - val = assigned_device_pci_cap_read_config(d, address, len);
>> - DEBUG("(%x.%x): address=%04x val=0x%08x len=%d\n",
>> - (d->devfn >> 3) & 0x1F, (d->devfn & 0x7), address, val, len);
>> - return val;
>> - }
>> -
>> - /*
>> - * Catch access to
>> - * - vendor & device ID
>> - * - base address registers
>> - * - ROM base address
>> - */
>> - if (ranges_overlap(address, len, PCI_VENDOR_ID, 4) ||
>> - ranges_overlap(address, len, PCI_BASE_ADDRESS_0, 24) ||
>> - ranges_overlap(address, len, PCI_ROM_ADDRESS, 4)) {
>> - val = pci_default_read_config(d, address, len);
>> - DEBUG("(%x.%x): address=%04x val=0x%08x len=%d\n",
>> - (d->devfn >> 3) & 0x1F, (d->devfn & 0x7), address, val, len);
>> - return val;
>> - }
>> -
>> - fd = pci_dev->real_device.config_fd;
>> -
>> -again:
>> - ret = pread(fd, &val, len, address);
>> - if (ret != len) {
>> - if ((ret < 0) && (errno == EINTR || errno == EAGAIN))
>> - goto again;
>> -
>> - fprintf(stderr, "%s: pread failed, ret = %zd errno = %d\n",
>> - __func__, ret, errno);
>> -
>> - exit(1);
>> - }
>> -
>> - DEBUG("(%x.%x): address=%04x val=0x%08x len=%d\n",
>> - (d->devfn >> 3) & 0x1F, (d->devfn & 0x7), address, val, len);
>> -
>> - if (pci_dev->emulate_cmd_mask) {
>> - val = merge_bits(val, pci_default_read_config(d, address, len),
>> - address, len, PCI_COMMAND, pci_dev->emulate_cmd_mask);
>> - }
>> -
>> - /*
>> - * Merge bits from virtualized
>> - * - capability pointer
>> - * - interrupt line & pin
>> - */
>> - virt_val = pci_default_read_config(d, address, len);
>> - val = merge_bits(val, virt_val, address, len, PCI_CAPABILITY_LIST, 0xff);
>> - val = merge_bits(val, virt_val, address, len, PCI_INTERRUPT_LINE, 0xffff);
>> -
>> - if (!pci_dev->cap.available) {
>> - /* kill the special capabilities */
>> - if (address == PCI_COMMAND && len == 4) {
>> - val &= ~(PCI_STATUS_CAP_LIST << 16);
>> - } else if (address == PCI_STATUS) {
>> - val &= ~PCI_STATUS_CAP_LIST;
>> - }
>> - }
>> -
>> - return val;
>> -}
>> -
>> static int assigned_dev_register_regions(PCIRegion *io_regions,
>> unsigned long regions_num,
>> AssignedDevice *pci_dev)
>> @@ -790,7 +624,8 @@ again:
>> /* dealing with virtual function device */
>> snprintf(name, sizeof(name), "%sphysfn/", dir);
>> if (!stat(name, &statbuf)) {
>> - pci_dev->emulate_cmd_mask = 0xffff;
>> + /* always provide the written value on readout */
>> + memset(pci_dev->direct_config_read + PCI_COMMAND, 0xff, 2);
>> }
>>
>> dev->region_number = r;
>> @@ -1268,73 +1103,81 @@ static void assigned_dev_update_msix(PCIDevice *pci_dev)
>> }
>> }
>>
>> -/* There can be multiple VNDR capabilities per device, we need to find the
>> - * one that starts closet to the given address without going over. */
>> -static uint8_t find_vndr_start(PCIDevice *pci_dev, uint32_t address)
>> +static uint32_t assigned_dev_pci_read_config(PCIDevice *pci_dev,
>> + uint32_t address, int len)
>> {
>> - uint8_t cap, pos;
>> + AssignedDevice *assigned_dev = DO_UPCAST(AssignedDevice, dev, pci_dev);
>> + uint32_t virt_val = pci_default_read_config(pci_dev, address, len);
>> + uint32_t real_val, direct_mask;
>>
>> - for (cap = pos = 0;
>> - (pos = pci_find_cap_offset(pci_dev, PCI_CAP_ID_VNDR, pos));
>> - pos += PCI_CAP_LIST_NEXT) {
>> - if (pos <= address) {
>> - cap = MAX(pos, cap);
>> - }
>> + switch (len) {
>> + case 4:
>> + direct_mask =
>> + pci_get_long(assigned_dev->direct_config_read + address);
>> + break;
>> + case 2:
>> + direct_mask =
>> + pci_get_word(assigned_dev->direct_config_read + address);
>> + break;
>> + case 1:
>> + direct_mask =
>> + pci_get_byte(assigned_dev->direct_config_read + address);
>> + break;
>> + default:
>> + abort();
>> }
>> - return cap;
>> -}
>> -
>> -static uint32_t assigned_device_pci_cap_read_config(PCIDevice *pci_dev,
>> - uint32_t address, int len)
>> -{
>> - uint8_t cap, cap_id = pci_dev->config_map[address];
>> - uint32_t val;
>> -
>> - switch (cap_id) {
>> -
>> - case PCI_CAP_ID_VPD:
>> - cap = pci_find_capability(pci_dev, cap_id);
>> - val = assigned_dev_pci_read(pci_dev, address, len);
>> - return merge_bits(val, pci_get_long(pci_dev->config + address),
>> - address, len, cap + PCI_CAP_LIST_NEXT, 0xff);
>> -
>> - case PCI_CAP_ID_VNDR:
>> - cap = find_vndr_start(pci_dev, address);
>> - val = assigned_dev_pci_read(pci_dev, address, len);
>> - return merge_bits(val, pci_get_long(pci_dev->config + address),
>> - address, len, cap + PCI_CAP_LIST_NEXT, 0xff);
>> + if (direct_mask) {
>> + real_val = assigned_dev_pci_read(pci_dev, address, len);
>> + return (virt_val & ~direct_mask) | (real_val & direct_mask);
>> + } else {
>> + return virt_val;
>> }
>> -
>> - return pci_default_read_config(pci_dev, address, len);
>> }
>>
>> -static void assigned_device_pci_cap_write_config(PCIDevice *pci_dev,
>> - uint32_t address,
>> - uint32_t val, int len)
>> +static void assigned_dev_pci_write_config(PCIDevice *pci_dev, uint32_t address,
>> + uint32_t val, int len)
>> {
>> - uint8_t cap_id = pci_dev->config_map[address];
>> + AssignedDevice *assigned_dev = DO_UPCAST(AssignedDevice, dev, pci_dev);
>> + uint32_t direct_mask, full_access;
>>
>> pci_default_write_config(pci_dev, address, val, len);
>> - switch (cap_id) {
>> - case PCI_CAP_ID_MSI:
>> +
>> + if (assigned_dev->cap.available & ASSIGNED_DEVICE_CAP_MSI) {
>> if (range_covers_byte(address, len,
>> pci_dev->msi_cap + PCI_MSI_FLAGS)) {
>> assigned_dev_update_msi(pci_dev);
>> }
>> - break;
>> -
>> - case PCI_CAP_ID_MSIX:
>> + } else if (assigned_dev->cap.available & ASSIGNED_DEVICE_CAP_MSIX) {
>> if (range_covers_byte(address, len,
>> pci_dev->msix_cap + PCI_MSIX_FLAGS + 1)) {
>> assigned_dev_update_msix(pci_dev);
>> }
>> - break;
>> + }
>>
>> - case PCI_CAP_ID_VPD:
>> - case PCI_CAP_ID_VNDR:
>> - assigned_dev_pci_write(pci_dev, address, val, len);
>> + switch (len) {
>> + case 4:
>> + direct_mask =
>> + pci_get_long(assigned_dev->direct_config_write + address);
>> + full_access = 0xffffffff;
>> + break;
>> + case 2:
>> + direct_mask =
>> + pci_get_word(assigned_dev->direct_config_write + address);
>> + full_access = 0xffff;
>> break;
>> + case 1:
>> + direct_mask =
>> + pci_get_byte(assigned_dev->direct_config_write + address);
>> + full_access = 0xff;
>> + break;
>> + default:
>> + abort();
>> + }
>> + if (direct_mask != full_access) {
>> + val &= direct_mask;
>> + val |= assigned_dev_pci_read(pci_dev, address, len) & ~direct_mask;
>> }
>> + assigned_dev_pci_write(pci_dev, address, val, len);
>
> I think we should not write at all for fully virtualized fields
> (direct_mask == 0). E.g. PCI BARs.

Yes, Alex caught that as well. Fixed already.

>
>> }
>>
>> static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>> @@ -1404,6 +1247,10 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>> return ret;
>> }
>>
>> + /* direct read except for next cap pointer */
>> + memset(dev->direct_config_read + pos, 0xff, PCI_PM_SIZEOF);
>> + dev->direct_config_read[pos + PCI_CAP_LIST_NEXT] = 0;
>> +
>> pmc = pci_get_word(pci_dev->config + pos + PCI_CAP_FLAGS);
>> pmc &= (PCI_PM_CAP_VER_MASK | PCI_PM_CAP_DSI);
>> pci_set_word(pci_dev->config + pos + PCI_CAP_FLAGS, pmc);
>> @@ -1438,6 +1285,10 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>> return ret;
>> }
>>
>> + /* direct read except for next cap pointer */
>> + memset(dev->direct_config_read + pos, 0xff, size);
>> + dev->direct_config_read[pos + PCI_CAP_LIST_NEXT] = 0;
>> +
>> type = pci_get_word(pci_dev->config + pos + PCI_EXP_FLAGS);
>> type = (type & PCI_EXP_FLAGS_TYPE) >> 8;
>> if (type != PCI_EXP_TYPE_ENDPOINT &&
>> @@ -1513,6 +1364,10 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>> return ret;
>> }
>>
>> + /* direct read except for next cap pointer */
>> + memset(dev->direct_config_read + pos, 0xff, 8);
>> + dev->direct_config_read[pos + PCI_CAP_LIST_NEXT] = 0;
>> +
>> /* Command register, clear upper bits, including extended modes */
>> cmd = pci_get_word(pci_dev->config + pos + PCI_X_CMD);
>> cmd &= (PCI_X_CMD_DPERR_E | PCI_X_CMD_ERO | PCI_X_CMD_MAX_READ |
>> @@ -1534,6 +1389,13 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>> if ((ret = pci_add_capability(pci_dev, PCI_CAP_ID_VPD, pos, 8)) < 0) {
>> return ret;
>> }
>> +
>> + /* direct read except for next cap pointer */
>> + memset(dev->direct_config_read + pos, 0xff, 8);
>> + dev->direct_config_read[pos + PCI_CAP_LIST_NEXT] = 0;
>> +
>> + /* direct write for cap content */
>> + memset(dev->direct_config_write + pos + 2, 0xff, 6);
>> }
>>
>> /* Devices can have multiple vendor capabilities, get them all */
>> @@ -1545,6 +1407,21 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
>> pos, len)) < 0) {
>> return ret;
>> }
>> +
>> + /* direct read except for next cap pointer */
>> + memset(dev->direct_config_read + pos, 0xff, len);
>> + dev->direct_config_read[pos + PCI_CAP_LIST_NEXT] = 0;
>
> Add a function for the above 3 lines?
>
>> +
>> + /* direct write for cap content */
>> + memset(dev->direct_config_write + pos + 2, 0xff, len - 2);
>> + }
>> +
>> + /* If real and virtual capability list status bits differ, virtualize the
>> + * access. */
>> + if ((pci_get_word(pci_dev->config + PCI_STATUS) & PCI_STATUS_CAP_LIST) !=
>> + (assigned_dev_pci_read_byte(pci_dev, PCI_STATUS) &
>> + PCI_STATUS_CAP_LIST)) {
>> + dev->direct_config_read[PCI_STATUS] &= ~PCI_STATUS_CAP_LIST;
>> }
>
> Is this an optimization? What harm does it do to virtualize always?

Just replicating the old behavior, but I can virtualize it unconditionally.

>
>>
>> return 0;
>> @@ -1694,6 +1571,26 @@ static int assigned_initfn(struct PCIDevice *pci_dev)
>> return -1;
>> }
>>
>> + /*
>> + * Set up basic config space access control. Will be further refined during
>> + * device initialization.
>> + *
>> + * Direct read/write access is grangted for:
>
> typo
>
>> + * - status & command registers, revision ID & class code, cacheline size,
>> + * latency timer, header type, BIST
>> + * - cardbus CIS pointer, subsystem vendor & ID
>> + * - reserved fields
>> + * - Min_Gnt & Max_Lat
>> + */
>> + memset(dev->direct_config_read + PCI_COMMAND, 0xff, 12);
>> + memset(dev->direct_config_read + PCI_CARDBUS_CIS, 0xff, 8);
>> + memset(dev->direct_config_read + PCI_CAPABILITY_LIST + 1, 0xff, 7);
>> + memset(dev->direct_config_read + PCI_MIN_GNT, 0xff, 2);
>> + memset(dev->direct_config_write + PCI_COMMAND, 0xff, 12);
>> + memset(dev->direct_config_write + PCI_CARDBUS_CIS, 0xff, 8);
>> + memset(dev->direct_config_write + PCI_CAPABILITY_LIST + 1, 0xff, 7);
>> + memset(dev->direct_config_write + PCI_MIN_GNT, 0xff, 2);
>> +
>> if (get_real_device(dev, dev->host.seg, dev->host.bus,
>> dev->host.dev, dev->host.func)) {
>> error_report("pci-assign: Error: Couldn't get real device (%s)!",
>> diff --git a/hw/device-assignment.h b/hw/device-assignment.h
>> index 3d20207..ed5defb 100644
>> --- a/hw/device-assignment.h
>> +++ b/hw/device-assignment.h
>> @@ -104,12 +104,13 @@ typedef struct AssignedDevice {
>> #define ASSIGNED_DEVICE_MSIX_MASKED (1 << 2)
>> uint32_t state;
>> } cap;
>> + uint8_t direct_config_read[PCI_CONFIG_SPACE_SIZE];
>> + uint8_t direct_config_write[PCI_CONFIG_SPACE_SIZE];
>
> What direct means isn't obvious. Add a comment?

Ok.

>
> We could revert the logic, have bits for
> emulate_config_read/emulate_config_write. I think that most of the
> registers can safely be read/written directly, so protecting relevant
> bits will be less work. Is that true?

I intentionally chose whitelisting to avoid accidentally granting access
to forgotten fields. I don't think it's a good idea to switch to
blacklisting.

Jan

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