[xen stable-4.17] xen/arm32: flushtlb: Reduce scope of barrier for local TLB flush

[patchbot@xxxxxxx]

commit 08157db12beb4a9698f4a13cba0884c4fe86f832
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Tue Jan 24 19:26:09 2023 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Jun 4 22:29:13 2026 +0100

    xen/arm32: flushtlb: Reduce scope of barrier for local TLB flush
    
    Per G5-9224 in ARM DDI 0487I.a:
    
    "A DSB NSH is sufficient to ensure completion of TLB maintenance
     instructions that apply to a single PE. A DSB ISH is sufficient to
     ensure completion of TLB maintenance instructions that apply to PEs
     in the same Inner Shareable domain.
    "
    
    This is quoting the Armv8 specification because I couldn't find an
    explicit statement in the Armv7 specification. Instead, I could find
    bits in various places that confirm the same implementation.
    
    Furthermore, Linux has been using 'nsh' since 2013 (62cbbc42e001
    "ARM: tlb: reduce scope of barrier domains for TLB invalidation").
    
    This means barrier after local TLB flushes could be reduced to
    non-shareable.
    
    Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
    Tested-by: Henry Wang <Henry.Wang@xxxxxxx>
    (cherry picked from commit d56c70b6e1fe2b4ee836ca4449a3277cbbeb0ddc)
    
    xen/arm: Remove stray semicolon at VREG_REG_HELPERS/TLB_HELPER* callers
    
    This is inconsistent with the rest of the code where macros are used
    to define functions, as it results in an empty declaration (i.e.
    semicolon with nothing before it) after function definition. This is also
    not allowed by C99.
    
    Take the opportunity to undefine TLB_HELPER* macros after last use.
    
    Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    (cherry picked from commit 6044b485ba5b0e4073a773402cedc2f2fae540ad)
---
 xen/arch/arm/include/asm/arm32/flushtlb.h | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/xen/arch/arm/include/asm/arm32/flushtlb.h 
b/xen/arch/arm/include/asm/arm32/flushtlb.h
index 9085e65011..22ee3b317b 100644
--- a/xen/arch/arm/include/asm/arm32/flushtlb.h
+++ b/xen/arch/arm/include/asm/arm32/flushtlb.h
@@ -15,30 +15,35 @@
  * For the Stage-2 page-tables the ISB ensures the completion of the DSB
  * (and therefore the TLB invalidation) before continuing. So we know
  * the TLBs cannot contain an entry for a mapping we may have removed.
+ *
+ * Note that for local TLB flush, using non-shareable (nsh) is sufficient
+ * (see G5-9224 in ARM DDI 0487I.a).
  */
-#define TLB_HELPER(name, tlbop) \
-static inline void name(void)   \
-{                               \
-    dsb(ishst);                 \
-    WRITE_CP32(0, tlbop);       \
-    dsb(ish);                   \
-    isb();                      \
+#define TLB_HELPER(name, tlbop, sh) \
+static inline void name(void)       \
+{                                   \
+    dsb(sh ## st);                  \
+    WRITE_CP32(0, tlbop);           \
+    dsb(sh);                        \
+    isb();                          \
 }
 
 /* Flush local TLBs, current VMID only */
-TLB_HELPER(flush_guest_tlb_local, TLBIALL);
+TLB_HELPER(flush_guest_tlb_local, TLBIALL, nsh)
 
 /* Flush inner shareable TLBs, current VMID only */
-TLB_HELPER(flush_guest_tlb, TLBIALLIS);
+TLB_HELPER(flush_guest_tlb, TLBIALLIS, ish)
 
 /* Flush local TLBs, all VMIDs, non-hypervisor mode */
-TLB_HELPER(flush_all_guests_tlb_local, TLBIALLNSNH);
+TLB_HELPER(flush_all_guests_tlb_local, TLBIALLNSNH, nsh)
 
 /* Flush innershareable TLBs, all VMIDs, non-hypervisor mode */
-TLB_HELPER(flush_all_guests_tlb, TLBIALLNSNHIS);
+TLB_HELPER(flush_all_guests_tlb, TLBIALLNSNHIS, ish)
 
 /* Flush all hypervisor mappings from the TLB of the local processor. */
-TLB_HELPER(flush_xen_tlb_local, TLBIALLH);
+TLB_HELPER(flush_xen_tlb_local, TLBIALLH, nsh)
+
+#undef TLB_HELPER
 
 /* Flush TLB of local processor for address va. */
 static inline void __flush_xen_tlb_one_local(vaddr_t va)
--
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