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target/riscv: Add M-mode virtual interrupt and IRQ filtering support.

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This change adds support for inserting virtual interrupts from M-mode
into S-mode using mvien and mvip csrs. IRQ filtering is a use case of
this change, i-e M-mode can stop delegating an interrupt to S-mode and
instead enable it in MIE and receive those interrupts in M-mode and then
selectively inject the interrupt using mvien and mvip.

Also, the spec doesn't mandate the interrupt to be actually supported
in hardware. Which allows M-mode to assert virtual interrupts to S-mode
that have no connection to any real interrupt events.

This is defined as part of the AIA specification [0], "5.3 Interrupt
filtering and virtual interrupts for supervisor level".

[0]: https://github.com/riscv/riscv-aia/releases/download/1.0/riscv-interrupts-1.0.pdf

Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20231016111736.28721-6-rkanwal@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Rajnesh Kanwal 2023-10-16 12:17:35 +01:00 • committed by Alistair Francis
parent 1ebad505f3
commit 1697837ed9
6 changed files with 291 additions and 38 deletions
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3
target/riscv/cpu.c
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@ -813,7 +813,8 @@ static bool riscv_cpu_has_work(CPUState *cs)
* Definition of the WFI instruction requires it to ignore the privilege
* mode and delegation registers, but respect individual enables
*/
return riscv_cpu_all_pending(env) != 0;
return riscv_cpu_all_pending(env) != 0 ||
riscv_cpu_sirq_pending(env) != RISCV_EXCP_NONE;
#else
return true;
#endif