LoongArch: KVM: Return full old CSR value from kvm_emu_xchg_csr()

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The LoongArch CSRXCHG instruction returns the full old CSR value in rd
after applying the masked update. kvm_emu_xchg_csr() currently masks
the saved value before returning it to the guest, so rd receives only
the bits selected by the write mask.

That breaks the architectural behavior and makes a zero mask return 0
instead of the previous CSR value. So, keep the masked CSR update, but
return the unmodified old CSR value.

Cc: stable@vger.kernel.org
Fixes: da50f5a693 ("LoongArch: KVM: Implement handle csr exception")
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Qiang Ma <maqianga@uniontech.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

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Qiang Ma 2026-06-11 20:46:43 +08:00 • committed by Huacai Chen

parent fb89e0fe2d

commit ebd50de14f

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arch/loongarch/kvm/exit.c

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