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Tsirkin" To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Cc: linux-kernel@vger.kernel.org, slp@redhat.com, bhe@redhat.com, somlo@cmu.edu, xiaolong.ye@intel.com Subject: Re: [PATCH v15 10/11] fw_cfg: write vmcoreinfo details Message-ID: <20180227022549-mutt-send-email-mst@kernel.org> References: <20180215213312.29234-1-marcandre.lureau@redhat.com> <20180215213312.29234-11-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180215213312.29234-11-marcandre.lureau@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Tue, 27 Feb 2018 00:28:30 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Tue, 27 Feb 2018 00:28:30 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mst@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 15, 2018 at 10:33:11PM +0100, Marc-Andr? 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-Andr? Lureau > --- > drivers/firmware/qemu_fw_cfg.c | 143 ++++++++++++++++++++++++++++++++++++++++- > include/uapi/linux/fw_cfg.h | 31 +++++++++ > 2 files changed, 171 insertions(+), 3 deletions(-) > > diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c > index c28bec4b5663..3015e77aebca 100644 > --- a/drivers/firmware/qemu_fw_cfg.c > +++ b/drivers/firmware/qemu_fw_cfg.c > @@ -34,11 +34,17 @@ > #include > #include > #include > +#include > +#include > +#include > > MODULE_AUTHOR("Gabriel L. Somlo "); > 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; > @@ -60,6 +66,64 @@ static void fw_cfg_sel_endianness(u16 key) > iowrite16(key, fw_cfg_reg_ctrl); > } > > +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) > +{ > + for (;;) { > + u32 ctrl = be32_to_cpu(READ_ONCE(d->control)); > + > + /* do not reorder the read to d->control */ > + rmb(); > + if ((ctrl & ~FW_CFG_DMA_CTL_ERROR) == 0) > + return; > + > + cpu_relax(); > + } > +} > + > +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 ssize_t fw_cfg_read_blob(u16 key, > void *buf, loff_t pos, size_t count) > @@ -89,6 +153,47 @@ static ssize_t fw_cfg_read_blob(u16 key, > return count; > } > > +#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 { > + fw_cfg_sel_endianness(key); > + 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) > { > @@ -188,9 +293,6 @@ 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); > @@ -213,6 +315,32 @@ 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 qemu documentation probably should mention that it must. > + */ > + 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) > { > @@ -452,6 +580,15 @@ 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) > diff --git a/include/uapi/linux/fw_cfg.h b/include/uapi/linux/fw_cfg.h > index c698ac3812f6..e089c0159ec2 100644 > --- a/include/uapi/linux/fw_cfg.h > +++ b/include/uapi/linux/fw_cfg.h > @@ -54,6 +54,7 @@ > > /* FW_CFG_ID bits */ > #define FW_CFG_VERSION 0x01 > +#define FW_CFG_VERSION_DMA 0x02 > > /* fw_cfg file directory entry type */ > struct fw_cfg_file { > @@ -63,4 +64,34 @@ struct fw_cfg_file { > char name[FW_CFG_MAX_FILE_PATH]; > }; > > +/* FW_CFG_DMA_CONTROL bits */ > +#define FW_CFG_DMA_CTL_ERROR 0x01 > +#define FW_CFG_DMA_CTL_READ 0x02 > +#define FW_CFG_DMA_CTL_SKIP 0x04 > +#define FW_CFG_DMA_CTL_SELECT 0x08 > +#define FW_CFG_DMA_CTL_WRITE 0x10 > + > +#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647ULL /* "QEMU CFG" */ > + > +/* Control as first field allows for different structures selected by this > + * field, which might be useful in the future > + */ > +struct fw_cfg_dma_access { > + __be32 control; > + __be32 length; > + __be64 address; > +}; > + > +#define FW_CFG_VMCOREINFO_FILENAME "etc/vmcoreinfo" > + > +#define FW_CFG_VMCOREINFO_FORMAT_NONE 0x0 > +#define FW_CFG_VMCOREINFO_FORMAT_ELF 0x1 > + > +struct fw_cfg_vmcoreinfo { > + __le16 host_format; > + __le16 guest_format; > + __le32 size; > + __le64 paddr; > +}; > + > #endif > -- > 2.16.1.73.g5832b7e9f2