Hi On Thu, Feb 15, 2018 at 7:09 PM, Michael S. Tsirkin <m...@redhat.com> wrote: > On Wed, Feb 14, 2018 at 03:18:49PM +0100, Marc-André Lureau wrote: >> If the "etc/vmcoreinfo" fw_cfg file is present and we are not running >> the kdump kernel, write the addr/size of the vmcoreinfo ELF note. >> >> The DMA operation is expected to run synchronously with today qemu, >> but the specification states that it may become async, so we run >> "control" field check in a loop for eventual changes. >> >> Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com> >> --- >> drivers/firmware/qemu_fw_cfg.c | 144 >> ++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 141 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c >> index 37638b95cb45..69939e2529f2 100644 >> --- a/drivers/firmware/qemu_fw_cfg.c >> +++ b/drivers/firmware/qemu_fw_cfg.c >> @@ -34,11 +34,17 @@ >> #include <linux/io.h> >> #include <linux/ioport.h> >> #include <linux/fw_cfg.h> >> +#include <linux/delay.h> >> +#include <linux/crash_dump.h> >> +#include <linux/crash_core.h> >> >> MODULE_AUTHOR("Gabriel L. Somlo <so...@cmu.edu>"); >> MODULE_DESCRIPTION("QEMU fw_cfg sysfs support"); >> MODULE_LICENSE("GPL"); >> >> +/* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */ >> +static u32 fw_cfg_rev; >> + >> /* fw_cfg device i/o register addresses */ >> static bool fw_cfg_is_mmio; >> static phys_addr_t fw_cfg_p_base; >> @@ -59,6 +65,65 @@ static inline u16 fw_cfg_sel_endianness(u16 key) >> (u16 __force)cpu_to_le16(key); >> } >> >> +static inline bool fw_cfg_dma_enabled(void) >> +{ >> + return (fw_cfg_rev & FW_CFG_VERSION_DMA) && fw_cfg_reg_dma; >> +} >> + >> +/* qemu fw_cfg device is sync today, but spec says it may become async */ >> +static void fw_cfg_wait_for_control(struct fw_cfg_dma_access *d) >> +{ >> + do { >> + u32 ctrl = be32_to_cpu(READ_ONCE(d->control)); >> + >> + if ((ctrl & ~FW_CFG_DMA_CTL_ERROR) == 0) >> + return; >> + >> + usleep_range(50, 100); > > I would just do cpu_relax() here.
ok, I didn't know that one. > >> + } while (true); >> + >> + /* do not reorder the read to d->control */ >> + rmb(); > > Hmm. I don't really understand the comment. > Is this code ever reacheable? How does it help? I thought that's what you suggested in v13 review, but true, I should replace the return with a break to reach it. Is that what you expect too? (my understanding is to make sure the READ_ONCE(control) in wait_for_control happens before READ_ONCE(control) after in dma_transfer) > >> +} >> + >> +static ssize_t fw_cfg_dma_transfer(void *address, u32 length, u32 control) >> +{ >> + phys_addr_t dma; >> + struct fw_cfg_dma_access *d = NULL; >> + ssize_t ret = length; >> + >> + d = kmalloc(sizeof(*d), GFP_KERNEL); >> + if (!d) { >> + ret = -ENOMEM; >> + goto end; >> + } >> + >> + /* fw_cfg device does not need IOMMU protection, so use physical >> addresses */ >> + *d = (struct fw_cfg_dma_access) { >> + .address = cpu_to_be64(address ? virt_to_phys(address) : 0), >> + .length = cpu_to_be32(length), >> + .control = cpu_to_be32(control) >> + }; >> + >> + dma = virt_to_phys(d); >> + >> + iowrite32be((u64)dma >> 32, fw_cfg_reg_dma); >> + /* force memory to sync before notifying device via MMIO */ >> + wmb(); >> + iowrite32be(dma, fw_cfg_reg_dma + 4); >> + >> + fw_cfg_wait_for_control(d); >> + >> + if (be32_to_cpu(READ_ONCE(d->control)) & FW_CFG_DMA_CTL_ERROR) { >> + ret = -EIO; >> + } >> + >> +end: >> + kfree(d); >> + >> + return ret; >> +} >> + >> /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */ >> static inline void fw_cfg_read_blob(u16 key, >> void *buf, loff_t pos, size_t count) >> @@ -87,6 +152,47 @@ static inline void fw_cfg_read_blob(u16 key, >> acpi_release_global_lock(glk); >> } >> >> +#ifdef CONFIG_CRASH_CORE >> +/* write chunk of given fw_cfg blob (caller responsible for sanity-check) */ >> +static ssize_t fw_cfg_write_blob(u16 key, >> + void *buf, loff_t pos, size_t count) >> +{ >> + u32 glk = -1U; >> + acpi_status status; >> + ssize_t ret = count; >> + >> + /* If we have ACPI, ensure mutual exclusion against any potential >> + * device access by the firmware, e.g. via AML methods: >> + */ >> + status = acpi_acquire_global_lock(ACPI_WAIT_FOREVER, &glk); >> + if (ACPI_FAILURE(status) && status != AE_NOT_CONFIGURED) { >> + /* Should never get here */ >> + WARN(1, "%s: Failed to lock ACPI!\n", __func__); >> + return -EINVAL; >> + } >> + >> + mutex_lock(&fw_cfg_dev_lock); >> + if (pos == 0) { >> + ret = fw_cfg_dma_transfer(buf, count, key << 16 >> + | FW_CFG_DMA_CTL_SELECT >> + | FW_CFG_DMA_CTL_WRITE); >> + } else { >> + iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl); >> + ret = fw_cfg_dma_transfer(NULL, pos, FW_CFG_DMA_CTL_SKIP); >> + if (ret < 0) >> + goto end; >> + ret = fw_cfg_dma_transfer(buf, count, FW_CFG_DMA_CTL_WRITE); >> + } >> + >> +end: >> + mutex_unlock(&fw_cfg_dev_lock); >> + >> + acpi_release_global_lock(glk); >> + >> + return ret; >> +} >> +#endif /* CONFIG_CRASH_CORE */ >> + >> /* clean up fw_cfg device i/o */ >> static void fw_cfg_io_cleanup(void) >> { >> @@ -185,9 +291,6 @@ static int fw_cfg_do_platform_probe(struct >> platform_device *pdev) >> return 0; >> } >> >> -/* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */ >> -static u32 fw_cfg_rev; >> - >> static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char >> *buf) >> { >> return sprintf(buf, "%u\n", fw_cfg_rev); >> @@ -210,6 +313,32 @@ struct fw_cfg_sysfs_entry { >> struct list_head list; >> }; >> >> +#ifdef CONFIG_CRASH_CORE >> +static ssize_t fw_cfg_write_vmcoreinfo(const struct fw_cfg_file *f) >> +{ >> + static struct fw_cfg_vmcoreinfo *data; >> + ssize_t ret; >> + >> + data = kmalloc(sizeof(struct fw_cfg_vmcoreinfo), GFP_KERNEL); >> + if (!data) >> + return -ENOMEM; >> + >> + *data = (struct fw_cfg_vmcoreinfo) { >> + .guest_format = cpu_to_le16(FW_CFG_VMCOREINFO_FORMAT_ELF), >> + .size = cpu_to_le32(VMCOREINFO_NOTE_SIZE), >> + .paddr = cpu_to_le64(paddr_vmcoreinfo_note()) >> + }; >> + /* spare ourself reading host format support for now since we >> + * don't know what else to format - host may ignore ours >> + */ >> + ret = fw_cfg_write_blob(be16_to_cpu(f->select), data, >> + 0, sizeof(struct fw_cfg_vmcoreinfo)); >> + >> + kfree(data); >> + return ret; >> +} >> +#endif /* CONFIG_CRASH_CORE */ >> + >> /* get fw_cfg_sysfs_entry from kobject member */ >> static inline struct fw_cfg_sysfs_entry *to_entry(struct kobject *kobj) >> { >> @@ -450,6 +579,15 @@ static int fw_cfg_register_file(const struct >> fw_cfg_file *f) >> int err; >> struct fw_cfg_sysfs_entry *entry; >> >> +#ifdef CONFIG_CRASH_CORE >> + if (fw_cfg_dma_enabled() && >> + strcmp(f->name, FW_CFG_VMCOREINFO_FILENAME) == 0 && >> + !is_kdump_kernel()) { >> + if (fw_cfg_write_vmcoreinfo(f) < 0) >> + pr_warn("fw_cfg: failed to write vmcoreinfo"); >> + } >> +#endif >> + >> /* allocate new entry */ >> entry = kzalloc(sizeof(*entry), GFP_KERNEL); >> if (!entry) >> -- >> 2.16.1.73.g5832b7e9f2