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Message-ID: <tip-cd95ea81f25608c403052d0508ee5c9b32e2bc7d@git.kernel.org>
Date: Tue, 1 Nov 2016 00:15:49 -0700
From: tip-bot for Andy Lutomirski <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: rusty@...tcorp.com.au, tglx@...utronix.de, brgerst@...il.com,
mingo@...nel.org, luto@...nel.org, riel@...hat.com,
pbonzini@...hat.com, oleg@...hat.com, fenghua.yu@...el.com,
linux-kernel@...r.kernel.org, peterz@...radead.org,
dvlasenk@...hat.com, jpoimboe@...hat.com, kvm@...r.kernel.org,
bp@...en8.de, torvalds@...ux-foundation.org, hpa@...or.com,
dave.hansen@...ux.intel.com, quentin.casasnovas@...cle.com
Subject: [tip:x86/fpu] x86/fpu, lguest: Remove CR0.TS support
Commit-ID: cd95ea81f25608c403052d0508ee5c9b32e2bc7d
Gitweb: http://git.kernel.org/tip/cd95ea81f25608c403052d0508ee5c9b32e2bc7d
Author: Andy Lutomirski <luto@...nel.org>
AuthorDate: Mon, 31 Oct 2016 15:18:46 -0700
Committer: Ingo Molnar <mingo@...nel.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 <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@...cle.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: kvm list <kvm@...r.kernel.org>
Link: http://lkml.kernel.org/r/8a7bf2c11231c082258fd67705d0f275639b8475.1477951965.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.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. */
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