[xen staging-4.21] ARM: Drop ThumbEE support

[patchbot@xxxxxxx]

commit a2eea8fd9e64afb733874c0a5634828570bb1061
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Mar 26 11:08:04 2026 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 26 11:08:04 2026 +0100

    ARM: Drop ThumbEE support
    
    Hans reports that Xen no longer builds on Debian unstable/sid:
    
      Assembler messages:
      {standard input}:474: Error: unknown or missing system register name at 
operand 1 -- `msr TEECR32_EL1,x0'
      {standard input}:480: Error: unknown or missing system register name at 
operand 1 -- `msr TEEHBR32_EL1,x0'
      {standard input}:488: Error: unknown or missing system register name at 
operand 2 -- `mrs x0,TEECR32_EL1'
      {standard input}:494: Error: unknown or missing system register name at 
operand 2 -- `mrs x0,TEEHBR32_EL1'
      make[5]: *** [Rules.mk:249: arch/arm/domain.o] Error 1
    
    This turns out to be an intentional change in binutils.  ThumbEE was dropped
    ahead of ARM v8 (i.e. AArch64).
    
    Xen supports ARM v7+virt extensions so in principle we could #ifdef
    CONFIG_ARM_32 to keep it working.  However, there was apparently no use of
    ThumbEE outside of demo code, so simply drop it.
    
    On ThumbEE capable hardware, unconditionally trap ThumbEE instructions, and
    drop the context switching logic for TEE{CR,HBR}32.
    
    Reported-by: Hans van Kranenburg <hans@xxxxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
    
    xen/arm: Set ThumbEE as not present in PFR0
    
    Force ThumbEE support to not available in the version of the PFR0
    register value we present to guest.
    Xen does not support ThumbEE and will trap all access to ThumbEE
    registers so do not report it being supported if the hardware supports
    it.
    
    Fixes: 5bbe1fe413f9 ("ARM: Drop ThumbEE support")
    Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
    Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
    Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
    Tested-by: Luca Fancellu <luca.fancellu@xxxxxxx>
    master commit: 5bbe1fe413f9d6a841b0bc70db024b1398391630
    master date: 2025-12-05 18:06:19 +0000
    master commit: 1ecb5946bdf8797d43ac6730c708bd105fdb0be4
    master date: 2026-01-05 10:33:03 +0000
---
 xen/arch/arm/cpufeature.c            |  3 +++
 xen/arch/arm/domain.c                | 12 ------------
 xen/arch/arm/include/asm/domain.h    |  1 -
 xen/arch/arm/include/asm/processor.h |  1 +
 xen/arch/arm/traps.c                 |  4 ++--
 5 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
index 1a80738571..94d14fb6a9 100644
--- a/xen/arch/arm/cpufeature.c
+++ b/xen/arch/arm/cpufeature.c
@@ -227,6 +227,9 @@ static int __init create_domain_cpuinfo(void)
 #endif
     domain_cpuinfo.pfr32.amu = 0;
 
+    /* Hide ThumbEE support */
+    domain_cpuinfo.pfr32.thumbee = 0;
+
     /* Hide RAS support as Xen does not support it */
 #ifdef CONFIG_ARM_64
     domain_cpuinfo.pfr64.ras = 0;
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index e36719bce4..38d7768de9 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -111,12 +111,6 @@ static void ctxt_switch_from(struct vcpu *p)
     p->arch.cntkctl = READ_SYSREG(CNTKCTL_EL1);
     virt_timer_save(p);
 
-    if ( is_32bit_domain(p->domain) && cpu_has_thumbee )
-    {
-        p->arch.teecr = READ_SYSREG(TEECR32_EL1);
-        p->arch.teehbr = READ_SYSREG(TEEHBR32_EL1);
-    }
-
 #ifdef CONFIG_ARM_32
     p->arch.joscr = READ_CP32(JOSCR);
     p->arch.jmcr = READ_CP32(JMCR);
@@ -244,12 +238,6 @@ static void ctxt_switch_to(struct vcpu *n)
     WRITE_SYSREG(n->arch.tpidrro_el0, TPIDRRO_EL0);
     WRITE_SYSREG(n->arch.tpidr_el1, TPIDR_EL1);
 
-    if ( is_32bit_domain(n->domain) && cpu_has_thumbee )
-    {
-        WRITE_SYSREG(n->arch.teecr, TEECR32_EL1);
-        WRITE_SYSREG(n->arch.teehbr, TEEHBR32_EL1);
-    }
-
 #ifdef CONFIG_ARM_32
     WRITE_CP32(n->arch.joscr, JOSCR);
     WRITE_CP32(n->arch.jmcr, JMCR);
diff --git a/xen/arch/arm/include/asm/domain.h 
b/xen/arch/arm/include/asm/domain.h
index af3e168374..758ad807e4 100644
--- a/xen/arch/arm/include/asm/domain.h
+++ b/xen/arch/arm/include/asm/domain.h
@@ -211,7 +211,6 @@ struct arch_vcpu
     register_t hcr_el2;
     register_t mdcr_el2;
 
-    uint32_t teecr, teehbr; /* ThumbEE, 32-bit guests only */
 #ifdef CONFIG_ARM_32
     /*
      * ARMv8 only supports a trivial implementation on Jazelle when in AArch32
diff --git a/xen/arch/arm/include/asm/processor.h 
b/xen/arch/arm/include/asm/processor.h
index 92c8bc1a31..ec23fd098b 100644
--- a/xen/arch/arm/include/asm/processor.h
+++ b/xen/arch/arm/include/asm/processor.h
@@ -411,6 +411,7 @@
 
 /* HSTR Hyp. System Trap Register */
 #define HSTR_T(x)       ((_AC(1,U)<<(x)))       /* Trap Cp15 c<x> */
+#define HSTR_TTEE       (_AC(1,U)<<16)          /* Trap ThumbEE */
 
 /* HDCR Hyp. Debug Configuration Register */
 #define HDCR_TDRA       (_AC(1,U)<<11)          /* Trap Debug ROM access */
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 2bc3e1df04..040c0f2e0d 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -158,8 +158,8 @@ void init_traps(void)
     WRITE_SYSREG(HDCR_TDRA|HDCR_TDOSA|HDCR_TDA|HDCR_TPM|HDCR_TPMCR,
                  MDCR_EL2);
 
-    /* Trap CP15 c15 used for implementation defined registers */
-    WRITE_SYSREG(HSTR_T(15), HSTR_EL2);
+    /* Trap CP15 c15 used for implementation defined registers, and ThumbEE. */
+    WRITE_SYSREG(HSTR_T(15) | (cpu_has_thumbee ? HSTR_TTEE : 0), HSTR_EL2);
 
     WRITE_SYSREG(get_default_cptr_flags(), CPTR_EL2);
 
--
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