Re: [Xen-devel] [PATCH] xen: arm: Fixing ttbcr (TCR_EL1 for AArch64) size.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-12-03 at 13:47 +0000, Ian Campbell wrote:
> On Tue, 2013-12-03 at 17:33 +0530, Pranavkumar Sawargaonkar wrote:
> > This patch fixes size of ttbcr register (TCR_EL1 in case of AArch64)
> > and it's programming considering size in case of context switch.
> > 
> > Currently ttbcr is defined as 32b register but for AArch64 TCR_EL1
> > size is 64b.
> 
> Thanks for tracking this down.
> 
> > Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxx>
> > Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@xxxxxxxxxx>
> [...]
> > diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> > index d5cae2e..2aa4443 100644
> > --- a/xen/include/asm-arm/domain.h
> > +++ b/xen/include/asm-arm/domain.h
> > @@ -165,7 +165,11 @@ struct arch_vcpu
> >  
> >      /* MMU */
> >      register_t vbar;
> > +#ifdef CONFIG_ARM_32
> >      uint32_t ttbcr;
> > +#else
> > +    uint64_t ttbcr;
> > +#endif
> 
> I think that actually only this hunk is required. 

Actually, it turns out there a few other places where ttbcr is
incorrectly stored in a 32-bit variable. Including one which needed some
careful consideration before it was safe to change. Here is what I came
up with.

-------------8<---------------

From 832544695c39a7d3f98e73381010eaab491982cc Mon Sep 17 00:00:00 2001
From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Tue, 3 Dec 2013 15:13:36 +0000
Subject: [PATCH] xen: arm: TCR_EL1 is 64-bit on arm64

Storing it in a 32-bit variable in struct arch_vcpu caused breakage over
context switch.

There were also several other places which stored this as the 32-bit value.
Update them all.

The "struct vcpu_guest_context" case needs special consideration. This struct
is in theory is exposed to guests, via the VCPUOP_initialise hypercall.
However as discussed in
http://lists.xen.org/archives/html/xen-devel/2013-10/msg00912.html this isn't
really a guest visible interface since ARM uses PSCI for VCPU bringup
(VCPUOP_initialise simply isn't available) The other users of this interface
are the domctls, which are not a stable API. Therefore while fixing the ttbcr
size also surround the struct in ifdefs to restrict the struct to the
hypervisor and the tools only (omitting the extra complexity of renaming as I
suggested in the referenced thread)

NB TCR_EL1 on arm64 is known as TTBCR on arm32, hence the apparent naming
inconsistencies.

Spotted-by: Pranavkumar Sawargaonkar <pranavkumar@xxxxxxxxxx>
Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Anup Patel <anup.patel@xxxxxxxxxx>
Cc: patches@xxxxxxxxxx
Cc: patches@xxxxxxx
---
 xen/arch/arm/traps.c          |   11 ++++++-----
 xen/include/asm-arm/domain.h  |    2 +-
 xen/include/public/arch-arm.h |    6 ++++--
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 53eb0cf..b2725df 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -330,7 +330,8 @@ static void inject_undef64_exception(struct cpu_user_regs 
*regs, int instr_len)
 
 struct reg_ctxt {
     /* Guest-side state */
-    uint32_t sctlr_el1, tcr_el1;
+    uint32_t sctlr_el1;
+    register_t tcr_el1;
     uint64_t ttbr0_el1, ttbr1_el1;
 #ifdef CONFIG_ARM_32
     uint32_t dfsr, ifsr;
@@ -433,7 +434,7 @@ static void show_registers_32(struct cpu_user_regs *regs,
     if ( guest_mode )
     {
         printk("     SCTLR: %08"PRIx32"\n", ctxt->sctlr_el1);
-        printk("       TCR: %08"PRIx32"\n", ctxt->tcr_el1);
+        printk("       TCR: %08"PRIregister"\n", ctxt->tcr_el1);
         printk("     TTBR0: %016"PRIx64"\n", ctxt->ttbr0_el1);
         printk("     TTBR1: %016"PRIx64"\n", ctxt->ttbr1_el1);
         printk("      IFAR: %08"PRIx32", IFSR: %08"PRIx32"\n"
@@ -505,7 +506,7 @@ static void show_registers_64(struct cpu_user_regs *regs,
         printk("   FAR_EL1: %016"PRIx64"\n", ctxt->far);
         printk("\n");
         printk(" SCTLR_EL1: %08"PRIx32"\n", ctxt->sctlr_el1);
-        printk("   TCR_EL1: %08"PRIx32"\n", ctxt->tcr_el1);
+        printk("   TCR_EL1: %08"PRIregister"\n", ctxt->tcr_el1);
         printk(" TTBR0_EL1: %016"PRIx64"\n", ctxt->ttbr0_el1);
         printk(" TTBR1_EL1: %016"PRIx64"\n", ctxt->ttbr1_el1);
         printk("\n");
@@ -1261,14 +1262,14 @@ static void do_sysreg(struct cpu_user_regs *regs,
 
 void dump_guest_s1_walk(struct domain *d, vaddr_t addr)
 {
-    uint32_t ttbcr = READ_SYSREG32(TCR_EL1);
+    register_t ttbcr = READ_SYSREG(TCR_EL1);
     uint64_t ttbr0 = READ_SYSREG64(TTBR0_EL1);
     paddr_t paddr;
     uint32_t offset;
     uint32_t *first = NULL, *second = NULL;
 
     printk("dom%d VA 0x%08"PRIvaddr"\n", d->domain_id, addr);
-    printk("    TTBCR: 0x%08"PRIx32"\n", ttbcr);
+    printk("    TTBCR: 0x%08"PRIregister"\n", ttbcr);
     printk("    TTBR0: 0x%016"PRIx64" = 0x%"PRIpaddr"\n",
            ttbr0, p2m_lookup(d, ttbr0 & PAGE_MASK));
 
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index d5cae2e..8ebee3e 100644
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -165,7 +165,7 @@ struct arch_vcpu
 
     /* MMU */
     register_t vbar;
-    uint32_t ttbcr;
+    register_t ttbcr;
     uint64_t ttbr0, ttbr1;
 
     uint32_t dacr; /* 32-bit guests only */
diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
index cb41ddc..475cb4a 100644
--- a/xen/include/public/arch-arm.h
+++ b/xen/include/public/arch-arm.h
@@ -278,6 +278,7 @@ typedef uint64_t xen_pfn_t;
 typedef uint64_t xen_ulong_t;
 #define PRI_xen_ulong PRIx64
 
+#if defined(__XEN__) || defined(__XEN_TOOLS__)
 struct vcpu_guest_context {
 #define _VGCF_online                   0
 #define VGCF_online                    (1<<_VGCF_online)
@@ -285,11 +286,12 @@ struct vcpu_guest_context {
 
     struct vcpu_guest_core_regs user_regs;  /* Core CPU registers */
 
-    uint32_t sctlr, ttbcr;
-    uint64_t ttbr0, ttbr1;
+    uint32_t sctlr;
+    uint64_t ttbcr, ttbr0, ttbr1;
 };
 typedef struct vcpu_guest_context vcpu_guest_context_t;
 DEFINE_XEN_GUEST_HANDLE(vcpu_guest_context_t);
+#endif
 
 struct arch_vcpu_info {
 };
-- 
1.7.10.4




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