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lguest: update comments

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Also removes a long-unused #define and an extraneous semicolon.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2011-07-22 14:39:50 +09:30
parent 3c3ed482dc
commit 9f54288def
9 changed files with 50 additions and 39 deletions
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12
Documentation/virtual/lguest/lguest.c
View file

@ -51,7 +51,7 @@
#include <asm/bootparam.h>
#include "../../../include/linux/lguest_launcher.h"
/*L:110
* We can ignore the 42 include files we need for this program, but I do want
* We can ignore the 43 include files we need for this program, but I do want
* to draw attention to the use of kernel-style types.
*
* As Linus said, "C is a Spartan language, and so should your naming be." I
@ -65,7 +65,6 @@ typedef uint16_t u16;
typedef uint8_t u8;
/*:*/
#define PAGE_PRESENT 0x7 /* Present, RW, Execute */
#define BRIDGE_PFX "bridge:"
#ifndef SIOCBRADDIF
#define SIOCBRADDIF 0x89a2 /* add interface to bridge */
@ -1359,7 +1358,7 @@ static void setup_console(void)
* --sharenet=<name> option which opens or creates a named pipe. This can be
* used to send packets to another guest in a 1:1 manner.
*
* More sopisticated is to use one of the tools developed for project like UML
* More sophisticated is to use one of the tools developed for project like UML
* to do networking.
*
* Faster is to do virtio bonding in kernel. Doing this 1:1 would be
@ -1369,7 +1368,7 @@ static void setup_console(void)
* multiple inter-guest channels behind one interface, although it would
* require some manner of hotplugging new virtio channels.
*
* Finally, we could implement a virtio network switch in the kernel.
* Finally, we could use a virtio network switch in the kernel, ie. vhost.
:*/
static u32 str2ip(const char *ipaddr)
@ -2006,10 +2005,7 @@ int main(int argc, char *argv[])
/* Tell the entry path not to try to reload segment registers. */
boot->hdr.loadflags |= KEEP_SEGMENTS;
/*
* We tell the kernel to initialize the Guest: this returns the open
* /dev/lguest file descriptor.
*/
/* We tell the kernel to initialize the Guest. */
tell_kernel(start);
/* Ensure that we terminate if a device-servicing child dies. */

1
arch/x86/include/asm/lguest_hcall.h
View file

@ -61,6 +61,7 @@ hcall(unsigned long call,
: "memory");
return call;
}
/*:*/
/* Can't use our min() macro here: needs to be a constant */
#define LGUEST_IRQS (NR_IRQS < 32 ? NR_IRQS: 32)

21
arch/x86/lguest/boot.c
View file

@ -71,7 +71,8 @@
#include <asm/stackprotector.h>
#include <asm/reboot.h> /* for struct machine_ops */
/*G:010 Welcome to the Guest!
/*G:010
* Welcome to the Guest!
*
* The Guest in our tale is a simple creature: identical to the Host but
* behaving in simplified but equivalent ways. In particular, the Guest is the
@ -190,15 +191,23 @@ static void lazy_hcall4(unsigned long call,
#endif
/*G:036
* When lazy mode is turned off reset the per-cpu lazy mode variable and then
* issue the do-nothing hypercall to flush any stored calls.
:*/
* When lazy mode is turned off, we issue the do-nothing hypercall to
* flush any stored calls, and call the generic helper to reset the
* per-cpu lazy mode variable.
*/
static void lguest_leave_lazy_mmu_mode(void)
{
hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0, 0);
paravirt_leave_lazy_mmu();
}
/*
* We also catch the end of context switch; we enter lazy mode for much of
* that too, so again we need to flush here.
*
* (Technically, this is lazy CPU mode, and normally we're in lazy MMU
* mode, but unlike Xen, lguest doesn't care about the difference).
*/
static void lguest_end_context_switch(struct task_struct *next)
{
hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0, 0);
@ -640,7 +649,7 @@ static void lguest_write_cr4(unsigned long val)
/*
* The Guest calls this after it has set a second-level entry (pte), ie. to map
* a page into a process' address space. Wetell the Host the toplevel and
* a page into a process' address space. We tell the Host the toplevel and
* address this corresponds to. The Guest uses one pagetable per process, so
* we need to tell the Host which one we're changing (mm->pgd).
*/
@ -1139,7 +1148,7 @@ static struct notifier_block paniced = {
static __init char *lguest_memory_setup(void)
{
/*
*The Linux bootloader header contains an "e820" memory map: the
* The Linux bootloader header contains an "e820" memory map: the
* Launcher populated the first entry with our memory limit.
*/
e820_add_region(boot_params.e820_map[0].addr,

18
arch/x86/lguest/i386_head.S
View file

@ -6,18 +6,22 @@
#include <asm/processor-flags.h>
/*G:020
* Our story starts with the kernel booting into startup_32 in
* arch/x86/kernel/head_32.S. It expects a boot header, which is created by
* the bootloader (the Launcher in our case).
* Our story starts with the bzImage: booting starts at startup_32 in
* arch/x86/boot/compressed/head_32.S. This merely uncompresses the real
* kernel in place and then jumps into it: startup_32 in
* arch/x86/kernel/head_32.S. Both routines expects a boot header in the %esi
* register, which is created by the bootloader (the Launcher in our case).
*
* The startup_32 function does very little: it clears the uninitialized global
* C variables which we expect to be zero (ie. BSS) and then copies the boot
* header and kernel command line somewhere safe. Finally it checks the
* 'hardware_subarch' field. This was introduced in 2.6.24 for lguest and Xen:
* if it's set to '1' (lguest's assigned number), then it calls us here.
* header and kernel command line somewhere safe, and populates some initial
* page tables. Finally it checks the 'hardware_subarch' field. This was
* introduced in 2.6.24 for lguest and Xen: if it's set to '1' (lguest's
* assigned number), then it calls us here.
*
* WARNING: be very careful here! We're running at addresses equal to physical
* addesses (around 0), not above PAGE_OFFSET as most code expectes
* addesses (around 0), not above PAGE_OFFSET as most code expects
* (eg. 0xC0000000). Jumps are relative, so they're OK, but we can't touch any
* data without remembering to subtract __PAGE_OFFSET!
*

2
drivers/lguest/core.c
View file

@ -117,7 +117,7 @@ static __init int map_switcher(void)
/*
* Now the Switcher is mapped at the right address, we can't fail!
* Copy in the compiled-in Switcher code (from <arch>_switcher.S).
* Copy in the compiled-in Switcher code (from x86/switcher_32.S).
*/
memcpy(switcher_vma->addr, start_switcher_text,
end_switcher_text - start_switcher_text);

4
drivers/lguest/interrupts_and_traps.c
View file

@ -427,8 +427,8 @@ void pin_stack_pages(struct lg_cpu *cpu)
/*
* Direct traps also mean that we need to know whenever the Guest wants to use
* a different kernel stack, so we can change the IDT entries to use that
* stack. The IDT entries expect a virtual address, so unlike most addresses
* a different kernel stack, so we can change the guest TSS to use that
* stack. The TSS entries expect a virtual address, so unlike most addresses
* the Guest gives us, the "esp" (stack pointer) value here is virtual, not
* physical.
*

17
drivers/lguest/lguest_user.c
View file

@ -1,8 +1,10 @@
/*P:200 This contains all the /dev/lguest code, whereby the userspace launcher
* controls and communicates with the Guest. For example, the first write will
* tell us the Guest's memory layout and entry point. A read will run the
* Guest until something happens, such as a signal or the Guest doing a NOTIFY
* out to the Launcher.
/*P:200 This contains all the /dev/lguest code, whereby the userspace
* launcher controls and communicates with the Guest. For example,
* the first write will tell us the Guest's memory layout and entry
* point. A read will run the Guest until something happens, such as
* a signal or the Guest doing a NOTIFY out to the Launcher. There is
* also a way for the Launcher to attach eventfds to particular NOTIFY
* values instead of returning from the read() call.
:*/
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
@ -357,8 +359,8 @@ static int initialize(struct file *file, const unsigned long __user *input)
goto free_eventfds;
/*
* Initialize the Guest's shadow page tables, using the toplevel
* address the Launcher gave us. This allocates memory, so can fail.
* Initialize the Guest's shadow page tables. This allocates
* memory, so can fail.
*/
err = init_guest_pagetable(lg);
if (err)
@ -516,6 +518,7 @@ static const struct file_operations lguest_fops = {
.read = read,
.llseek = default_llseek,
};
/*:*/
/*
* This is a textbook example of a "misc" character device. Populate a "struct

4
drivers/lguest/page_tables.c
View file

@ -155,7 +155,7 @@ static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
}
/*
* These functions are just like the above two, except they access the Guest
* These functions are just like the above, except they access the Guest
* page tables. Hence they return a Guest address.
*/
static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr)
@ -195,7 +195,7 @@ static unsigned long gpte_addr(struct lg_cpu *cpu,
#endif
/*:*/
/*M:014
/*M:007
* get_pfn is slow: we could probably try to grab batches of pages here as
* an optimization (ie. pre-faulting).
:*/

10
drivers/lguest/x86/core.c
View file

@ -272,7 +272,7 @@ static int emulate_insn(struct lg_cpu *cpu)
unsigned int insnlen = 0, in = 0, shift = 0;
/*
* The eip contains the *virtual* address of the Guest's instruction:
* guest_pa just subtracts the Guest's page_offset.
* walk the Guest's page tables to find the "physical" address.
*/
unsigned long physaddr = guest_pa(cpu, cpu->regs->eip);
@ -409,7 +409,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
* These values mean a real interrupt occurred, in which case
* the Host handler has already been run. We just do a
* friendly check if another process should now be run, then
* return to run the Guest again
* return to run the Guest again.
*/
cond_resched();
return;
@ -459,7 +459,7 @@ void __init lguest_arch_host_init(void)
int i;
/*
* Most of the i386/switcher.S doesn't care that it's been moved; on
* Most of the x86/switcher_32.S doesn't care that it's been moved; on
* Intel, jumps are relative, and it doesn't access any references to
* external code or data.
*
@ -587,7 +587,7 @@ void __init lguest_arch_host_init(void)
clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
}
put_online_cpus();
};
}
/*:*/
void __exit lguest_arch_host_fini(void)
@ -670,8 +670,6 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu)
/*:*/
/*L:030
* lguest_arch_setup_regs()
*
* Most of the Guest's registers are left alone: we used get_zeroed_page() to
* allocate the structure, so they will be 0.
*/