Commit-ID: cd95ea81f25608c403052d0508ee5c9b32e2bc7d Gitweb: http://git.kernel.org/tip/cd95ea81f25608c403052d0508ee5c9b32e2bc7d Author: Andy Lutomirski <l...@kernel.org> AuthorDate: Mon, 31 Oct 2016 15:18:46 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 1 Nov 2016 07:47:54 +0100
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 <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Fenghua Yu <fenghua...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Oleg Nesterov <o...@redhat.com> Cc: Paolo Bonzini <pbonz...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Quentin Casasnovas <quentin.casasno...@oracle.com> Cc: Rik van Riel <r...@redhat.com> Cc: Rusty Russell <ru...@rustcorp.com.au> Cc: Thomas Gleixner <t...@linutronix.de> Cc: kvm list <k...@vger.kernel.org> Link: http://lkml.kernel.org/r/8a7bf2c11231c082258fd67705d0f275639b8475.1477951965.git.l...@kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/include/asm/lguest_hcall.h | 1 - arch/x86/lguest/boot.c | 17 +++++++---------- drivers/lguest/hypercalls.c | 4 ---- drivers/lguest/lg.h | 1 - drivers/lguest/x86/core.c | 19 +------------------ 5 files changed, 8 insertions(+), 34 deletions(-) diff --git a/arch/x86/include/asm/lguest_hcall.h b/arch/x86/include/asm/lguest_hcall.h index ef01fef..6c119cf 100644 --- a/arch/x86/include/asm/lguest_hcall.h +++ b/arch/x86/include/asm/lguest_hcall.h @@ -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 diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 25da5bc8..d74afcd 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -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; } /* diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c index 19a3228..601f81c 100644 --- a/drivers/lguest/hypercalls.c +++ b/drivers/lguest/hypercalls.c @@ -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; diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index 69b3814..2356a23 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -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; diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c index 6e9042e..743253f 100644 --- a/drivers/lguest/x86/core.c +++ b/drivers/lguest/x86/core.c @@ -247,14 +247,6 @@ 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 * won't try it because we don't advertise it in CPUID, but a malicious @@ -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. */
