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Currently, the common AIA functions kvm_riscv_vcpu_aia_has_interrupts()
and kvm_riscv_aia_wakeon_hgei() lookup HGEI line using an array of VCPU
pointers before accessing HGEI[E|P] CSR which is slow and prone to race
conditions because there is a separate per-hart lock for the VCPU pointer
array and a separate per-VCPU rwlock for IMSIC VS-file (including HGEI
line) used by the VCPU. Due to these race conditions, it is observed
on QEMU RISC-V host that Guest VCPUs sleep in WFI and never wakeup even
with interrupt pending in the IMSIC VS-file because VCPUs were waiting
for HGEI wakeup on the wrong host CPU.
The IMSIC virtualization already keeps track of the HGEI line and the
associated IMSIC VS-file used by each VCPU so move the HGEI[E|P] CSR
access to IMSIC virtualization so that costly HGEI line lookup can be
avoided and likelihood of race-conditions when updating HGEI[E|P] CSR
is also reduced.
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Fixes: 3385339296d1 ("RISC-V: KVM: Use IMSIC guest files when available")
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250707035345.17494-3-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
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Remove the unnecessary kick to the vCPU after writing to the vs_file
of IMSIC in kvm_riscv_vcpu_aia_imsic_inject.
For vCPUs that are running, writing to the vs_file directly forwards
the interrupt as an MSI to them and does not need an extra kick.
For vCPUs that are descheduled after emulating WFI, KVM will enable
the guest external interrupt for that vCPU in
kvm_riscv_aia_wakeon_hgei. This means that writing to the vs_file
will cause a guest external interrupt, which will cause KVM to wake
up the vCPU in hgei_interrupt to handle the interrupt properly.
Signed-off-by: BillXiang <xiangwencheng@lanxincomputing.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Radim Krčmář <rkrcmar@ventanamicro.com>
Link: https://lore.kernel.org/r/20250221104538.2147-1-xiangwencheng@lanxincomputing.com
Signed-off-by: Anup Patel <anup@brainfault.org>
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For the external interrupt updating procedure in imsic, there was a
spinlock to protect it already. But since it should not be preempted in
any cases, we should turn to use raw_spinlock to prevent any preemption
in case PREEMPT_RT was enabled.
Signed-off-by: Cyan Yang <cyan.yang@sifive.com>
Reviewed-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Message-ID: <20240919160126.44487-1-cyan.yang@sifive.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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We have common APLIC and IMSIC headers available under
include/linux/irqchip/ directory which are used by APLIC
and IMSIC irqchip drivers. Let us replace the use of
kvm_aia_*.h headers with include/linux/irqchip/riscv-*.h
headers.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Link: https://lore.kernel.org/r/20240411090639.237119-2-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
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The emulated IMSIC update the external interrupt pending depending on
the value of eidelivery and topei. It might lose an interrupt when it
is interrupted before setting the new value to the pending status.
For example, when VCPU0 sends an IPI to VCPU1 via IMSIC:
VCPU0 VCPU1
CSRSWAP topei = 0
The VCPU1 has claimed all the external
interrupt in its interrupt handler.
topei of VCPU1's IMSIC = 0
set pending in VCPU1's IMSIC
topei of VCPU1' IMSIC = 1
set the external interrupt
pending of VCPU1
clear the external interrupt pending
of VCPU1
When the VCPU1 switches back to VS mode, it exits the interrupt handler
because the result of CSRSWAP topei is 0. If there are no other external
interrupts injected into the VCPU1's IMSIC, VCPU1 will never know this
pending interrupt unless it initiative read the topei.
If the interruption occurs between updating interrupt pending in IMSIC
and updating external interrupt pending of VCPU, it will not cause a
problem. Suppose that the VCPU1 clears the IPI pending in IMSIC right
after VCPU0 sets the pending, the external interrupt pending of VCPU1
will not be set because the topei is 0. But when the VCPU1 goes back to
VS mode, the pending IPI will be reported by the CSRSWAP topei, it will
not lose this interrupt.
So we only need to make the external interrupt updating procedure as a
critical section to avoid the problem.
Fixes: db8b7e97d613 ("RISC-V: KVM: Add in-kernel virtualization of AIA IMSIC")
Tested-by: Roy Lin <roy.lin@sifive.com>
Tested-by: Wayling Chen <wayling.chen@sifive.com>
Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
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./arch/riscv/kvm/aia_imsic.c:94:2-3: Unneeded semicolon
./arch/riscv/kvm/aia_imsic.c:134:2-3: Unneeded semicolon
./arch/riscv/kvm/aia_imsic.c:173:2-3: Unneeded semicolon
./arch/riscv/kvm/aia_imsic.c:210:2-3: Unneeded semicolon
./arch/riscv/kvm/aia_imsic.c:296:2-3: Unneeded semicolon
./arch/riscv/kvm/aia_imsic.c:354:2-3: Unneeded semicolon
./arch/riscv/kvm/aia_device.c:105:4-5: Unneeded semicolon
./arch/riscv/kvm/aia_device.c:166:2-3: Unneeded semicolon
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=5569
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
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We expose IMSIC registers as KVM device attributes of the in-kernel
AIA irqchip device. This will allow KVM user-space to save/restore
IMISC state of each VCPU using KVM device ioctls().
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
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We can have AIA IMSIC support for both HS-level and VS-level but
the VS-level IMSICs are optional. We use the VS-level IMSICs for
Guest/VM whenever available otherwise we fallback to software
emulation of AIA IMSIC.
This patch adds in-kernel virtualization of AIA IMSIC.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
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