mirror of https://github.com/xemu-project/xemu.git
target/riscv/kvm.c: Fix the hart bit setting of AIA
In AIA spec, each hart (or each hart within a group) has a unique hart number to locate the memory pages of interrupt files in the address space. The number of bits required to represent any hart number is equal to ceil(log2(hmax + 1)), where hmax is the largest hart number among groups. However, if the largest hart number among groups is a power of 2, QEMU will pass an inaccurate hart-index-bit setting to Linux. For example, when the guest OS has 4 harts, only ceil(log2(3 + 1)) = 2 bits are sufficient to represent 4 harts, but we passes 3 to Linux. The code needs to be updated to ensure accurate hart-index-bit settings. Additionally, a Linux patch[1] is necessary to correctly recover the hart index when the guest OS has only 1 hart, where the hart-index-bit is 0. [1] https://lore.kernel.org/lkml/20240415064905.25184-1-yongxuan.wang@sifive.com/t/ Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com> Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Cc: qemu-stable <qemu-stable@nongnu.org> Message-ID: <20240515091129.28116-1-yongxuan.wang@sifive.com> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
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target/riscv/kvm
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@ -1777,7 +1777,14 @@ void kvm_riscv_aia_create(MachineState *machine, uint64_t group_shift,
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}
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}
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hart_bits = find_last_bit(&max_hart_per_socket, BITS_PER_LONG) + 1;
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if (max_hart_per_socket > 1) {
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max_hart_per_socket--;
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hart_bits = find_last_bit(&max_hart_per_socket, BITS_PER_LONG) + 1;
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} else {
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hart_bits = 0;
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}
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ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_CONFIG,
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KVM_DEV_RISCV_AIA_CONFIG_HART_BITS,
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&hart_bits, true, NULL);
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