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x86/fpu, lguest: Remove CR0.TS support 

Now that Linux never sets CR0.TS, lguest doesn't need to support it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm list <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/8a7bf2c11231c082258fd67705d0f275639b8475.1477951965.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2016-10-31 15:18:46 -07:00 committed by Ingo Molnar
parent 04ac88abaf
commit cd95ea81f2
5 changed files with 8 additions and 34 deletions
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1
arch/x86/include/asm/lguest_hcall.h
View File

@ -9,7 +9,6 @@
#define LHCALL_FLUSH_TLB 5
#define LHCALL_LOAD_IDT_ENTRY 6
#define LHCALL_SET_STACK 7
#define LHCALL_TS 8
#define LHCALL_SET_CLOCKEVENT 9
#define LHCALL_HALT 10
#define LHCALL_SET_PMD 13

17
arch/x86/lguest/boot.c
View File

@ -497,27 +497,24 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
* a whole series of functions like read_cr0() and write_cr0().
*
* We start with cr0. cr0 allows you to turn on and off all kinds of basic
* features, but Linux only really cares about one: the horrifically-named Task
* Switched (TS) bit at bit 3 (ie. 8)
* features, but the only cr0 bit that Linux ever used at runtime was the
* horrifically-named Task Switched (TS) bit at bit 3 (ie. 8)
*
* What does the TS bit do? Well, it causes the CPU to trap (interrupt 7) if
* the floating point unit is used. Which allows us to restore FPU state
* lazily after a task switch, and Linux uses that gratefully, but wouldn't a
* name like "FPUTRAP bit" be a little less cryptic?
* lazily after a task switch if we wanted to, but wouldn't a name like
* "FPUTRAP bit" be a little less cryptic?
*
* We store cr0 locally because the Host never changes it. The Guest sometimes
* wants to read it and we'd prefer not to bother the Host unnecessarily.
* Fortunately, Linux keeps it simple and doesn't use TS, so we can ignore
* cr0.
*/
static unsigned long current_cr0;
static void lguest_write_cr0(unsigned long val)
{
lazy_hcall1(LHCALL_TS, val & X86_CR0_TS);
current_cr0 = val;
}
static unsigned long lguest_read_cr0(void)
{
return current_cr0;
return 0;
}
/*

4
drivers/lguest/hypercalls.c
View File

@ -109,10 +109,6 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
case LHCALL_SET_CLOCKEVENT:
guest_set_clockevent(cpu, args->arg1);
break;
case LHCALL_TS:
/* This sets the TS flag, as we saw used in run_guest(). */
cpu->ts = args->arg1;
break;
case LHCALL_HALT:
/* Similarly, this sets the halted flag for run_guest(). */
cpu->halted = 1;

1
drivers/lguest/lg.h
View File

@ -43,7 +43,6 @@ struct lg_cpu {
struct mm_struct *mm; /* == tsk->mm, but that becomes NULL on exit */
u32 cr2;
int ts;
u32 esp1;
u16 ss1;

19
drivers/lguest/x86/core.c
View File

@ -246,14 +246,6 @@ unsigned long *lguest_arch_regptr(struct lg_cpu *cpu, size_t reg_off, bool any)
*/
void lguest_arch_run_guest(struct lg_cpu *cpu)
{
/*
* Remember the awfully-named TS bit? If the Guest has asked to set it
* we set it now, so we can trap and pass that trap to the Guest if it
* uses the FPU.
*/
if (cpu->ts && fpregs_active())
stts();
/*
* SYSENTER is an optimized way of doing system calls. We can't allow
* it because it always jumps to privilege level 0. A normal Guest
@ -282,10 +274,6 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
if (boot_cpu_has(X86_FEATURE_SEP))
wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
/* Clear the host TS bit if it was set above. */
if (cpu->ts && fpregs_active())
clts();
/*
* If the Guest page faulted, then the cr2 register will tell us the
* bad virtual address. We have to grab this now, because once we
@ -421,12 +409,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
kill_guest(cpu, "Writing cr2");
break;
case 7: /* We've intercepted a Device Not Available fault. */
/*
* If the Guest doesn't want to know, we already restored the
* Floating Point Unit, so we just continue without telling it.
*/
if (!cpu->ts)
return;
/* No special handling is needed here. */
break;
case 32 ... 255:
/* This might be a syscall. */