From: Rusty Russell Date: Wed, 11 Feb 2015 04:56:01 +0000 (+1030) Subject: lguest: use the PCI console device's emerg_wr for early boot messages. X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a561adfaecc9eb6fb66941b450458801f3f60ca0;p=linux-beck.git lguest: use the PCI console device's emerg_wr for early boot messages. This involves manually checking the console device (which is always in slot 1 of bus 0) and using the window in VIRTIO_PCI_CAP_PCI_CFG to program it (as we can't map the BAR yet). We could in fact do this much earlier, but we wait for the first write from the virtio_cons_early_init() facility. Signed-off-by: Rusty Russell --- diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 2943ab931671..531b844cb48d 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -57,6 +57,7 @@ #include #include #include +#include #include #include #include @@ -74,6 +75,7 @@ #include /* for struct machine_ops */ #include #include +#include /*G:010 * Welcome to the Guest! @@ -1202,25 +1204,145 @@ static __init char *lguest_memory_setup(void) return "LGUEST"; } +/* Offset within PCI config space of BAR access capability. */ +static int console_cfg_offset = 0; +static int console_access_cap; + +/* Set up so that we access off in bar0 (on bus 0, device 1, function 0) */ +static void set_cfg_window(u32 cfg_offset, u32 off) +{ + write_pci_config_byte(0, 1, 0, + cfg_offset + offsetof(struct virtio_pci_cap, bar), + 0); + write_pci_config(0, 1, 0, + cfg_offset + offsetof(struct virtio_pci_cap, length), + 4); + write_pci_config(0, 1, 0, + cfg_offset + offsetof(struct virtio_pci_cap, offset), + off); +} + +static u32 read_bar_via_cfg(u32 cfg_offset, u32 off) +{ + set_cfg_window(cfg_offset, off); + return read_pci_config(0, 1, 0, + cfg_offset + sizeof(struct virtio_pci_cap)); +} + +static void write_bar_via_cfg(u32 cfg_offset, u32 off, u32 val) +{ + set_cfg_window(cfg_offset, off); + write_pci_config(0, 1, 0, + cfg_offset + sizeof(struct virtio_pci_cap), val); +} + +static void probe_pci_console(void) +{ + u8 cap, common_cap = 0, device_cap = 0; + /* Offsets within BAR0 */ + u32 common_offset, device_offset; + + /* Avoid recursive printk into here. */ + console_cfg_offset = -1; + + if (!early_pci_allowed()) { + printk(KERN_ERR "lguest: early PCI access not allowed!\n"); + return; + } + + /* We expect a console PCI device at BUS0, slot 1. */ + if (read_pci_config(0, 1, 0, 0) != 0x10431AF4) { + printk(KERN_ERR "lguest: PCI device is %#x!\n", + read_pci_config(0, 1, 0, 0)); + return; + } + + /* Find the capabilities we need (must be in bar0) */ + cap = read_pci_config_byte(0, 1, 0, PCI_CAPABILITY_LIST); + while (cap) { + u8 vndr = read_pci_config_byte(0, 1, 0, cap); + if (vndr == PCI_CAP_ID_VNDR) { + u8 type, bar; + u32 offset; + + type = read_pci_config_byte(0, 1, 0, + cap + offsetof(struct virtio_pci_cap, cfg_type)); + bar = read_pci_config_byte(0, 1, 0, + cap + offsetof(struct virtio_pci_cap, bar)); + offset = read_pci_config(0, 1, 0, + cap + offsetof(struct virtio_pci_cap, offset)); + + switch (type) { + case VIRTIO_PCI_CAP_COMMON_CFG: + if (bar == 0) { + common_cap = cap; + common_offset = offset; + } + break; + case VIRTIO_PCI_CAP_DEVICE_CFG: + if (bar == 0) { + device_cap = cap; + device_offset = offset; + } + break; + case VIRTIO_PCI_CAP_PCI_CFG: + console_access_cap = cap; + break; + } + } + cap = read_pci_config_byte(0, 1, 0, cap + PCI_CAP_LIST_NEXT); + } + if (!common_cap || !device_cap || !console_access_cap) { + printk(KERN_ERR "lguest: No caps (%u/%u/%u) in console!\n", + common_cap, device_cap, console_access_cap); + return; + } + + +#define write_common_config(reg, val) \ + write_bar_via_cfg(console_access_cap, \ + common_offset+offsetof(struct virtio_pci_common_cfg,reg),\ + val) + +#define read_common_config(reg) \ + read_bar_via_cfg(console_access_cap, \ + common_offset+offsetof(struct virtio_pci_common_cfg,reg)) + + /* Check features: they must offer EMERG_WRITE */ + write_common_config(device_feature_select, 0); + + if (!(read_common_config(device_feature) + & (1 << VIRTIO_CONSOLE_F_EMERG_WRITE))) { + printk(KERN_ERR "lguest: console missing EMERG_WRITE\n"); + return; + } + + console_cfg_offset = device_offset; +} + /* * We will eventually use the virtio console device to produce console output, - * but before that is set up we use LHCALL_NOTIFY on normal memory to produce - * console output. + * but before that is set up we use the virtio PCI console's backdoor mmio + * access and the "emergency" write facility (which is legal even before the + * device is configured). */ static __init int early_put_chars(u32 vtermno, const char *buf, int count) { - char scratch[17]; - unsigned int len = count; + /* If we couldn't find PCI console, forget it. */ + if (console_cfg_offset < 0) + return count; - /* We use a nul-terminated string, so we make a copy. Icky, huh? */ - if (len > sizeof(scratch) - 1) - len = sizeof(scratch) - 1; - scratch[len] = '\0'; - memcpy(scratch, buf, len); - hcall(LHCALL_NOTIFY, __pa(scratch), 0, 0, 0); + if (unlikely(!console_cfg_offset)) { + probe_pci_console(); + if (console_cfg_offset < 0) + return count; + } - /* This routine returns the number of bytes actually written. */ - return len; + write_bar_via_cfg(console_access_cap, + console_cfg_offset + + offsetof(struct virtio_console_config, emerg_wr), + buf[0]); + return 1; } /*