[Xen-devel] [for-4.7 v2 2/2] xen/arm: traps: Correctly interpret the content of the register HPFAR_EL2

[Julien Grall <julien.grall@xxxxxxx>]

The register HPFAR_EL2 (resp. HPFAR on arm32) contains the bits [47:12]
(resp. [39:12]) of the faulting IPA. Unlike other registers that represent
an address, the upper bits of the IPA are stored in the register bits
[4:39] (resp. [4:21]).

However, Xen assumes that the register contains the faulting IPA correctly
offsetted. This will result to get a wrong IPA when the fault is happening
during a translation table walk. Note this is only affecting  memaccess.

Introduce a new helper to get the faulting IPA from HPFAR_EL2 and
replace direct read from the register by the helper.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
Cc: tamas@xxxxxxxxxxxxx

This is a bug fix for Xen 4.7 and should also be backported to Xen 4.6.
Without this patch, the faulting IPA reported to memaccess may be wrong.

    Changes in v2:
        - Add Andre's and Stefano's reviewed-by
---
 xen/arch/arm/traps.c            | 11 +++++++++--
 xen/include/asm-arm/processor.h |  7 +++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 1516abd..5e865cf 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2363,6 +2363,13 @@ done:
     if (first) unmap_domain_page(first);
 }
 
+static inline paddr_t get_faulting_ipa(void)
+{
+    register_t hpfar = READ_SYSREG(HPFAR_EL2);
+
+    return ((paddr_t)(hpfar & HPFAR_MASK) << (12 - 4));
+}
+
 static void do_trap_instr_abort_guest(struct cpu_user_regs *regs,
                                       const union hsr hsr)
 {
@@ -2381,7 +2388,7 @@ static void do_trap_instr_abort_guest(struct 
cpu_user_regs *regs,
         };
 
         if ( hsr.iabt.s1ptw )
-            gpa = READ_SYSREG(HPFAR_EL2);
+            gpa = get_faulting_ipa();
         else
         {
             /*
@@ -2431,7 +2438,7 @@ static void do_trap_data_abort_guest(struct cpu_user_regs 
*regs,
 #endif
 
     if ( dabt.s1ptw )
-        info.gpa = READ_SYSREG(HPFAR_EL2);
+        info.gpa = get_faulting_ipa();
     else
     {
         rc = gva_to_ipa(info.gva, &info.gpa, GV2M_READ);
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 7e6eb66..6789cd0 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -565,6 +565,13 @@ union hsr {
 
 #define FSC_LL_MASK    (_AC(0x03,U)<<0)
 
+/* HPFAR_EL2: Hypervisor IPA Fault Address Register */
+#ifdef CONFIG_ARM_64
+#define HPFAR_MASK     GENMASK(39, 4)
+#else
+#define HPFAR_MASK     GENMASK(31, 4)
+#endif
+
 /* Time counter hypervisor control register */
 #define CNTHCTL_EL2_EL1PCTEN (1u<<0) /* Kernel/user access to physical counter 
*/
 #define CNTHCTL_EL2_EL1PCEN  (1u<<1) /* Kernel/user access to CNTP timer regs 
*/
-- 
1.9.1


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