[xen master] xen/riscv: initialize bitmap to zero in riscv_fill_hwcap_from_isa_string()

[patchbot@xxxxxxx]

commit 2cdd22fd25a1f999fe5f054925ae03e3ab3c4f9d
Author:     Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
AuthorDate: Wed May 14 10:59:00 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed May 14 10:59:00 2025 +0200

    xen/riscv: initialize bitmap to zero in riscv_fill_hwcap_from_isa_string()
    
    The this_isa bitmap should be explicitly initialized to zero to avoid
    false positives when detecting supported ISA extensions. Without proper
    zero-initialization, the bitmap may retain non-zero values from
    uninitialized memory, causing Xen to incorrectly assume that certain
    extensions are supported.
    
    This change ensures reliable detection of ISA capabilities.
    
    Fixes: 0c2f717eae ("xen/riscv: identify specific ISA supported by cpu")
    Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/riscv/cpufeature.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/riscv/cpufeature.c b/xen/arch/riscv/cpufeature.c
index 5aafab0f49..3246a03624 100644
--- a/xen/arch/riscv/cpufeature.c
+++ b/xen/arch/riscv/cpufeature.c
@@ -405,6 +405,8 @@ static void __init riscv_fill_hwcap_from_isa_string(void)
         const char *isa;
         unsigned long cpuid;
 
+        bitmap_zero(this_isa, RISCV_ISA_EXT_MAX);
+
         if ( !dt_device_type_is_equal(cpu, "cpu") )
             continue;
 
--
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