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Message-Id: <1408587400-18663-3-git-send-email-mukesh.rathor@oracle.com>
Date: Wed, 20 Aug 2014 19:16:40 -0700
From: Mukesh Rathor <mukesh.rathor@...cle.com>
To: boris.ostrovsky@...cle.com, david.vrabel@...rix.com
Cc: xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: [V0 PATCH 2/2] AMD-PVH: set EFER.NX and EFER.SCE for secondary vcpus
The secondary vcpus come on kernel page tables which have the NX bit set
in pte entries for DS/SS. On AMD, EFER.NX must be set to avoid protection
fault.
Signed-off-by: Mukesh Rathor <mukesh.rathor@...cle.com>
---
arch/x86/xen/smp.c | 28 ++++++++++++++++++++--------
arch/x86/xen/smp.h | 1 +
arch/x86/xen/xen-head.S | 21 +++++++++++++++++++++
3 files changed, 42 insertions(+), 8 deletions(-)
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 7005974..66058b9 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;
@@ -416,12 +420,20 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
#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!
+ } else {
+ /*
+ * The vcpu comes on kernel page tables which have the NX pte
+ * bit set on AMD. 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)pvh_cpu_bringup;
+
+ /* 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;
+ }
#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..b20ba68 100644
--- a/arch/x86/xen/smp.h
+++ b/arch/x86/xen/smp.h
@@ -7,5 +7,6 @@ extern void xen_send_IPI_mask_allbutself(const struct cpumask *mask,
extern void xen_send_IPI_allbutself(int vector);
extern void xen_send_IPI_all(int vector);
extern void xen_send_IPI_self(int vector);
+extern void pvh_cpu_bringup(int cpu);
#endif
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 485b695..db8dca5 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -47,6 +47,27 @@ ENTRY(startup_xen)
__FINIT
+#ifdef CONFIG_XEN_PVH
+#ifdef CONFIG_X86_64
+/* Note that rdi contains the cpu number and must be preserved */
+ENTRY(pvh_cpu_bringup)
+ /* Gather features to see if NX implemented. (no EFER.NX on intel) */
+ movl $0x80000001, %eax
+ cpuid
+ movl %edx,%esi
+
+ movl $MSR_EFER, %ecx
+ rdmsr
+ btsl $_EFER_SCE, %eax
+
+ btl $20,%esi
+ jnc 1f /* No NX, skip it */
+ btsl $_EFER_NX, %eax
+1: wrmsr
+ jmp cpu_bringup_and_idle
+#endif /* CONFIG_X86_64 */
+#endif /* CONFIG_XEN_PVH */
+
.pushsection .text
.balign PAGE_SIZE
ENTRY(hypercall_page)
--
1.8.3.1
--
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