From: Yong-Xuan Wang <yongxuan.w...@sifive.com> 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.w...@sifive.com/t/ Signed-off-by: Yong-Xuan Wang <yongxuan.w...@sifive.com> Reviewed-by: Andrew Jones <ajo...@ventanamicro.com> Cc: qemu-stable <qemu-sta...@nongnu.org> Message-ID: <20240515091129.28116-1-yongxuan.w...@sifive.com> Signed-off-by: Alistair Francis <alistair.fran...@wdc.com> (cherry picked from commit 190b867f28cb5781f3cd01a3deb371e4211595b1) Signed-off-by: Michael Tokarev <m...@tls.msk.ru> diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c index 5187b88ad9..94b0e393bf 100644 --- a/target/riscv/kvm/kvm-cpu.c +++ b/target/riscv/kvm/kvm-cpu.c @@ -1671,7 +1671,14 @@ void kvm_riscv_aia_create(MachineState *machine, uint64_t group_shift, } } - hart_bits = find_last_bit(&max_hart_per_socket, BITS_PER_LONG) + 1; + + if (max_hart_per_socket > 1) { + max_hart_per_socket--; + hart_bits = find_last_bit(&max_hart_per_socket, BITS_PER_LONG) + 1; + } else { + hart_bits = 0; + } + ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_CONFIG, KVM_DEV_RISCV_AIA_CONFIG_HART_BITS, &hart_bits, true, NULL); -- 2.39.2
