6c8dca5d53
A non-periodic clock_event_device and the "jiffies" clock don't mix well: tick_handle_periodic() can go into an infinite loop. Currently lguest guests use the jiffies clock when the TSC is unusable. Instead, make the Host write the current time into the lguest page on every interrupt. This doesn't cost much but is more precise and at least as accurate as the jiffies clock. It also gets rid of the GET_WALLCLOCK hypercall. Also, delay setting sched_clock until our clock is set up, otherwise the early printk timestamps can go backwards (not harmful, just ugly). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
117 lines
4 KiB
C
117 lines
4 KiB
C
/* Things the lguest guest needs to know. Note: like all lguest interfaces,
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* this is subject to wild and random change between versions. */
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#ifndef _ASM_LGUEST_H
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#define _ASM_LGUEST_H
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#ifndef __ASSEMBLY__
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#include <asm/irq.h>
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#define LHCALL_FLUSH_ASYNC 0
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#define LHCALL_LGUEST_INIT 1
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#define LHCALL_CRASH 2
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#define LHCALL_LOAD_GDT 3
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#define LHCALL_NEW_PGTABLE 4
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#define LHCALL_FLUSH_TLB 5
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#define LHCALL_LOAD_IDT_ENTRY 6
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#define LHCALL_SET_STACK 7
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#define LHCALL_TS 8
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#define LHCALL_SET_CLOCKEVENT 9
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#define LHCALL_HALT 10
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#define LHCALL_BIND_DMA 12
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#define LHCALL_SEND_DMA 13
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#define LHCALL_SET_PTE 14
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#define LHCALL_SET_PMD 15
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#define LHCALL_LOAD_TLS 16
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#define LG_CLOCK_MIN_DELTA 100UL
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#define LG_CLOCK_MAX_DELTA ULONG_MAX
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/*G:031 First, how does our Guest contact the Host to ask for privileged
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* operations? There are two ways: the direct way is to make a "hypercall",
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* to make requests of the Host Itself.
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*
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* Our hypercall mechanism uses the highest unused trap code (traps 32 and
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* above are used by real hardware interrupts). Seventeen hypercalls are
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* available: the hypercall number is put in the %eax register, and the
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* arguments (when required) are placed in %edx, %ebx and %ecx. If a return
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* value makes sense, it's returned in %eax.
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*
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* Grossly invalid calls result in Sudden Death at the hands of the vengeful
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* Host, rather than returning failure. This reflects Winston Churchill's
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* definition of a gentleman: "someone who is only rude intentionally". */
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#define LGUEST_TRAP_ENTRY 0x1F
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static inline unsigned long
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hcall(unsigned long call,
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unsigned long arg1, unsigned long arg2, unsigned long arg3)
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{
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/* "int" is the Intel instruction to trigger a trap. */
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asm volatile("int $" __stringify(LGUEST_TRAP_ENTRY)
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/* The call is in %eax (aka "a"), and can be replaced */
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: "=a"(call)
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/* The other arguments are in %eax, %edx, %ebx & %ecx */
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: "a"(call), "d"(arg1), "b"(arg2), "c"(arg3)
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/* "memory" means this might write somewhere in memory.
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* This isn't true for all calls, but it's safe to tell
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* gcc that it might happen so it doesn't get clever. */
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: "memory");
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return call;
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}
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/*:*/
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void async_hcall(unsigned long call,
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unsigned long arg1, unsigned long arg2, unsigned long arg3);
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/* Can't use our min() macro here: needs to be a constant */
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#define LGUEST_IRQS (NR_IRQS < 32 ? NR_IRQS: 32)
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#define LHCALL_RING_SIZE 64
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struct hcall_ring
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{
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u32 eax, edx, ebx, ecx;
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};
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/*G:032 The second method of communicating with the Host is to via "struct
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* lguest_data". The Guest's very first hypercall is to tell the Host where
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* this is, and then the Guest and Host both publish information in it. :*/
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struct lguest_data
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{
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/* 512 == enabled (same as eflags in normal hardware). The Guest
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* changes interrupts so often that a hypercall is too slow. */
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unsigned int irq_enabled;
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/* Fine-grained interrupt disabling by the Guest */
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DECLARE_BITMAP(blocked_interrupts, LGUEST_IRQS);
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/* The Host writes the virtual address of the last page fault here,
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* which saves the Guest a hypercall. CR2 is the native register where
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* this address would normally be found. */
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unsigned long cr2;
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/* Wallclock time set by the Host. */
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struct timespec time;
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/* Async hypercall ring. Instead of directly making hypercalls, we can
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* place them in here for processing the next time the Host wants.
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* This batching can be quite efficient. */
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/* 0xFF == done (set by Host), 0 == pending (set by Guest). */
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u8 hcall_status[LHCALL_RING_SIZE];
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/* The actual registers for the hypercalls. */
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struct hcall_ring hcalls[LHCALL_RING_SIZE];
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/* Fields initialized by the Host at boot: */
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/* Memory not to try to access */
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unsigned long reserve_mem;
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/* ID of this Guest (used by network driver to set ethernet address) */
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u16 guestid;
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/* KHz for the TSC clock. */
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u32 tsc_khz;
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/* Fields initialized by the Guest at boot: */
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/* Instruction range to suppress interrupts even if enabled */
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unsigned long noirq_start, noirq_end;
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};
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extern struct lguest_data lguest_data;
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_LGUEST_H */
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