lguest: documentation VII: FIXMEs (f56a384e) · Commits · jan.koester / Linux

Documentation/lguest/lguest.c

+12 −0

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		@@ -1510,3 +1510,15 @@ int main(int argc, char *argv[])
		/* Finally, run the Guest. This doesn't return. */
		run_guest(lguest_fd, &device_list);
		}
		/:/

		/*M:999
		* Mastery is done: you now know everything I do.
		*
		* But surely you have seen code, features and bugs in your wanderings which
		* you now yearn to attack? That is the real game, and I look forward to you
		* patching and forking lguest into the Your-Name-Here-visor.
		*
		* Farewell, and good coding!
		* Rusty Russell.
		*/

+3 −0

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		@@ -13,6 +13,9 @@
		* functions.
		:*/

		/*M:002 The console can be flooded: while the Guest is processing input the
		* Host can send more. Buffering in the Host could alleviate this, but it is a
		* difficult problem in general. :*/
		/* Copyright (C) 2006 Rusty Russell, IBM Corporation
		*
		* This program is free software; you can redistribute it and/or modify

+14 −0

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		@@ -231,6 +231,20 @@ static int direct_trap(const struct lguest *lg,
		* go direct, of course 8) */
		return idt_type(trap->a, trap->b) == 0xF;
		}
		/:/

		/*M:005 The Guest has the ability to turn its interrupt gates into trap gates,
		* if it is careful. The Host will let trap gates can go directly to the
		* Guest, but the Guest needs the interrupts atomically disabled for an
		* interrupt gate. It can do this by pointing the trap gate at instructions
		* within noirq_start and noirq_end, where it can safely disable interrupts. */

		/*M:006 The Guests do not use the sysenter (fast system call) instruction,
		* because it's hardcoded to enter privilege level 0 and so can't go direct.
		* It's about twice as fast as the older "int 0x80" system call, so it might
		* still be worthwhile to handle it in the Switcher and lcall down to the
		* Guest. The sysenter semantics are hairy tho: search for that keyword in
		* entry.S :*/

		/*H:260 When we make traps go directly into the Guest, we need to make sure
		* the kernel stack is valid (ie. mapped in the page tables). Otherwise, the

+10 −0

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		@@ -553,6 +553,16 @@ void release_all_dma(struct lguest *lg)
		up_read(&lg->mm->mmap_sem);
		}

		/*M:007 We only return a single DMA buffer to the Launcher, but it would be
		* more efficient to return a pointer to the entire array of DMA buffers, which
		* it can cache and choose one whenever it wants.
		*
		* Currently the Launcher uses a write to /dev/lguest, and the return value is
		* the address of the DMA structure with the interrupt number placed in
		* dma->used_len. If we wanted to return the entire array, we need to return
		* the address, array size and interrupt number: this seems to require an
		* ioctl(). :*/

		/*L:320 This routine looks for a DMA buffer registered by the Guest on the
		* given key (using the BIND_DMA hypercall). */
		unsigned long get_dma_buffer(struct lguest *lg,

+8 −0

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		@@ -250,6 +250,14 @@ static void irq_enable(void)
		{
		lguest_data.irq_enabled = X86_EFLAGS_IF;
		}
		/:/
		/*M:003 Note that we don't check for outstanding interrupts when we re-enable
		* them (or when we unmask an interrupt). This seems to work for the moment,
		* since interrupts are rare and we'll just get the interrupt on the next timer
		* tick, but when we turn on CONFIG_NO_HZ, we should revisit this. One way
		* would be to put the "irq_enabled" field in a page by itself, and have the
		* Host write-protect it when an interrupt comes in when irqs are disabled.
		* There will then be a page fault as soon as interrupts are re-enabled. :*/

		/*G:034
		* The Interrupt Descriptor Table (IDT).