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Date: Wed, 3 Sep 2014 14:58:04 +0100
From: David Vrabel <david.vrabel@...rix.com>
To: Mukesh Rathor <mukesh.rathor@...cle.com>,
<boris.ostrovsky@...cle.com>, <david.vrabel@...rix.com>
CC: <xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [V2 PATCH 1/1] PVH: set EFER.NX and EFER.SCE
On 03/09/14 02:19, Mukesh Rathor wrote:
> This patch addresses two things for a pvh boot vcpu:
>
> - NX bug on intel: It was recenlty discovered that NX is not being
> honored in PVH on intel since EFER.NX is not being set.
>
> - PVH boot hang on newer xen: Following c/s on xen
>
> c/s 7645640: x86/PVH: don't set EFER_SCE for pvh guest
>
> removes setting of EFER.SCE for PVH guests. As such, existing intel
> pvh guest will no longer boot on xen after that c/s.
>
> Both above changes will be applicable to AMD also when xen support
> of AMD pvh is added.
>
> Also, we create a new glue assembly entry point for secondary vcpus
> because they come up on kernel page tables that have pte.NX
> bits set. As such, before anything is touched in DS/SS, EFER.NX
> must be set.
[...]
> --- a/arch/x86/xen/xen-head.S
> +++ b/arch/x86/xen/xen-head.S
> @@ -47,6 +47,35 @@ ENTRY(startup_xen)
>
> __FINIT
>
> +#ifdef CONFIG_XEN_PVH
> +#ifdef CONFIG_X86_64
> +.macro PVH_EARLY_SET_EFER
I don't think a macro is the right way to do this. We can instead pass
a parameter to say whether it is a boot or secondary CPU.
Something like this (untested) patch?
8<----------------------------
x86/xen: Set EFER.NX and EFER.SCE in PVH guests
This patch addresses two things for a pvh boot vcpu:
- NX bug on intel: It was recenlty discovered that NX is not being
honored in PVH on intel since EFER.NX is not being set.
- PVH boot hang on newer xen: Following c/s on xen
c/s 7645640: x86/PVH: don't set EFER_SCE for pvh guest
removes setting of EFER.SCE for PVH guests. As such, existing intel
pvh guest will no longer boot on xen after that c/s.
Both above changes will be applicable to AMD also when xen support
of AMD pvh is added.
Also, we create a new glue assembly entry point for secondary vcpus
because they come up on kernel page tables that have pte.NX
bits set. As such, before anything is touched in DS/SS, EFER.NX
must be set.
Signed-off-by: Mukesh Rathor <mukesh.rathor@...cle.com>
Signed-off-by: David Vrabel <david.vrabel@...rix.com>
---
arch/x86/xen/enlighten.c | 1 +
arch/x86/xen/smp.c | 34 +++++++++++++++++++++++-----------
arch/x86/xen/smp.h | 8 ++++++++
arch/x86/xen/xen-head.S | 34 ++++++++++++++++++++++++++++++++++
4 files changed, 66 insertions(+), 11 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index c0cb11f..b111035 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1508,6 +1508,7 @@ static void __init xen_pvh_early_guest_init(void)
return;
xen_have_vector_callback = 1;
+ xen_pvh_cpu_early_init(0, false);
xen_pvh_set_cr_flags(0);
#ifdef CONFIG_X86_32
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 7005974..dd4ce0d 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -37,6 +37,7 @@
#include <xen/hvc-console.h>
#include "xen-ops.h"
#include "mmu.h"
+#include "smp.h"
cpumask_var_t xen_cpu_initialized_map;
@@ -99,8 +100,12 @@ static void cpu_bringup(void)
wmb(); /* make sure everything is out */
}
-/* Note: cpu parameter is only relevant for PVH */
-static void cpu_bringup_and_idle(int cpu)
+/*
+ * Note: cpu parameter is only relevant for PVH. The reason for passing it
+ * is we can't do smp_processor_id until the percpu segments are loaded, for
+ * which we need the cpu number! So we pass it in rdi as first parameter.
+ */
+asmlinkage __visible void cpu_bringup_and_idle(int cpu)
{
#ifdef CONFIG_X86_64
if (xen_feature(XENFEAT_auto_translated_physmap) &&
@@ -374,11 +379,10 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
ctxt->user_regs.fs = __KERNEL_PERCPU;
ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
#endif
- ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
-
memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
ctxt->flags = VGCF_IN_KERNEL;
ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
ctxt->user_regs.ds = __USER_DS;
@@ -413,15 +417,23 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
(unsigned long)xen_failsafe_callback;
ctxt->user_regs.cs = __KERNEL_CS;
per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
-#ifdef CONFIG_X86_32
- }
-#else
- } else
- /* N.B. The user_regs.eip (cpu_bringup_and_idle) is called with
- * %rdi having the cpu number - which means are passing in
- * as the first parameter the cpu. Subtle!
+ }
+#ifdef CONFIG_X86_64
+ else {
+ /*
+ * The vcpu comes on kernel page tables which have the NX pte
+ * bit set. This means before DS/SS is touched, NX in
+ * EFER must be set. Hence the following assembly glue code.
+ */
+ ctxt->user_regs.eip = (unsigned long)xen_pvh_cpu_early_init;
+
+ /* N.B. The bringup function cpu_bringup_and_idle is called with
+ * %rdi having the cpu number - which means we are passing it in
+ * as the first parameter. Subtle!
*/
ctxt->user_regs.rdi = cpu;
+ ctxt->user_regs.rsi = 1; /* secondary_cpu == true */
+ }
#endif
ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
diff --git a/arch/x86/xen/smp.h b/arch/x86/xen/smp.h
index c7c2d89..fc2575a 100644
--- a/arch/x86/xen/smp.h
+++ b/arch/x86/xen/smp.h
@@ -8,4 +8,12 @@ extern void xen_send_IPI_allbutself(int vector);
extern void xen_send_IPI_all(int vector);
extern void xen_send_IPI_self(int vector);
+#if defined(CONFIG_XEN_PVH) && defined(CONFIG_X86_64)
+extern void xen_pvh_cpu_early_init(int cpu, bool secondary_cpu);
+#else
+static inline void xen_pvh_cpu_early_init(int cpu, bool secondary_cpu)
+{
+}
+#endif
+
#endif
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 485b695..a64b464 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -47,6 +47,40 @@ ENTRY(startup_xen)
__FINIT
+#ifdef CONFIG_XEN_PVH
+#ifdef CONFIG_X86_64
+
+/**
+ * xen_pvh_cpu_early_init() - early PVH VCPU initialization
+ * @cpu: this cpu number (%rdi)
+ * @secondary_cpu: true if this is a secondary (non-boot) CPU (%rsi)
+ *
+ * Note: This is called as a function on the boot CPU and as the secondary
+ * CPU entry point.
+ */
+ENTRY(xen_pvh_cpu_early_init)
+ mov %rsi, %r11
+ /* Gather features to see if NX implemented. */
+ mov $0x80000001, %eax
+ cpuid
+ mov %edx,%esi
+
+ mov $MSR_EFER, %ecx
+ rdmsr
+ bts $_EFER_SCE, %eax
+
+ bt $20,%esi
+ jnc 1f /* No NX, skip setting it */
+ bts $_EFER_NX, %eax
+1: wrmsr
+
+ cmp $0,%r11b /* non-zero => secondary cpu */
+ jne cpu_bringup_and_idle
+ ret
+
+#endif /* CONFIG_X86_64 */
+#endif /* CONFIG_XEN_PVH */
+
.pushsection .text
.balign PAGE_SIZE
ENTRY(hypercall_page)
--
1.7.10.4
--
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