hw/riscv/virt-acpi-build: Fix RINTC PLIC context ID for KVM

[PATCH] hw/riscv/virt-acpi-build: Fix RINTC PLIC context ID for KVM

Qingwei Hu posted 1 patch 3 days, 9 hours ago

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git fetch https://github.com/patchew-project/qemu tags/patchew/20260604120017.398890-1-qingwei.hu@bytedance.com

Maintainers: Sunil V L <sunilvl@ventanamicro.com>, Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Weiwei Li <liwei1518@gmail.com>, Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com>, Liu Zhiwei <zhiwei_liu@linux.alibaba.com>, Chao Liu <chao.liu.zevorn@gmail.com>

hw/riscv/virt-acpi-build.c | 2 ++
1 file changed, 2 insertions(+)

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[PATCH] hw/riscv/virt-acpi-build: Fix RINTC PLIC context ID for KVM

Posted by Qingwei Hu 3 days, 9 hours ago

Each RISC-V MADT RINTC entry contains an External Interrupt Controller
ID field. On the virt machine without AIA, this field identifies the
S-mode PLIC context associated with the hart.

TCG virt has both M-mode and S-mode PLIC contexts, so the S-mode context
ID is odd and 2 * local_cpu_id + 1 is correct. KVM virt exposes only
S-mode PLIC contexts, and those contexts are numbered contiguously from
0. Reporting the TCG context ID for KVM makes the guest enable a
different PLIC context from the one used by QEMU.

With ACPI enabled, this can leave PCI INTx interrupts pending in QEMU
while the guest-programmed PLIC context remains disabled. A virtio-blk
root disk can then stall during boot because its first interrupt is never
delivered.

Use local_cpu_id for KVM and keep the existing odd S-mode context ID for
TCG.

Fixes: d641da6ed43 ("hw/riscv/virt-acpi-build.c: Add PLIC in MADT")
Signed-off-by: Qingwei Hu <qingwei.hu@bytedance.com>
---
 hw/riscv/virt-acpi-build.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/riscv/virt-acpi-build.c b/hw/riscv/virt-acpi-build.c
index 413d47d70e..6b06d9aa87 100644
--- a/hw/riscv/virt-acpi-build.c
+++ b/hw/riscv/virt-acpi-build.c
@@ -100,6 +100,8 @@ static void riscv_acpi_madt_add_rintc(uint32_t uid,
         build_append_int_noprefix(entry,
                                   ACPI_BUILD_INTC_ID(
                                       arch_ids->cpus[uid].props.node_id,
+                                      kvm_enabled() ?
+                                      local_cpu_id :
                                       2 * local_cpu_id + 1),
                                   4);
     } else {
-- 
2.39.5