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From: Richard Henderson <richard.henderson@linaro.org>
To: Alistair Francis <alistair23@gmail.com>,
	Jonathan Behrens <fintelia@gmail.com>
Cc: Palmer Dabbelt <palmer@sifive.com>,
	"open list:RISC-V" <qemu-riscv@nongnu.org>,
	Anup Patel <Anup.Patel@wdc.com>,
	"qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
	Atish Patra <Atish.Patra@wdc.com>,
	Alistair Francis <Alistair.Francis@wdc.com>
Subject: Re: [Qemu-devel] [Qemu-riscv] [PATCH v1 10/28] target/riscv: Convert mie and mstatus to pointers
Date: Thu, 19 Sep 2019 07:50:12 -0700
Message-ID: <18b87754-d5b2-e4f1-bdc5-92ad26b97379@linaro.org> (raw)
In-Reply-To: <CAKmqyKPQPrPKdkaRjZ7P75jamuqEq6BABir56VrYGm=ZSFpAww@mail.gmail.com>

On 9/18/19 4:47 PM, Alistair Francis wrote:
> I'm not a fan of the pointer method that I'm using, but to me it seems
> the least worst in terms of handling future code, keeping everythign
> consistnent and avoiding complex access rules.

FWIW, I prefer the "banked" register method used by ARM.

enum {
    M_REG_NS = 0,    /* non-secure mode */
    M_REG_S = 1,     /* secure mode */
    M_REG_NUM_BANKS = 2,
};

...

        uint32_t vecbase[M_REG_NUM_BANKS];
        uint32_t basepri[M_REG_NUM_BANKS];
        uint32_t control[M_REG_NUM_BANKS];

The major difference that I see is that a pointer can only represent a single
state at a single time.  With an index, different parts of the code can ask
different questions that may have different states.  E.g. "are we currently in
secure mode" vs "will the exception return to secure mode".


r~


  reply index

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-23 23:37 [Qemu-devel] [PATCH v1 00/28] Add RISC-V Hypervisor Extension v0.4 Alistair Francis
2019-08-23 23:37 ` [Qemu-devel] [PATCH v1 01/28] target/riscv: Add the Hypervisor extension Alistair Francis
2019-08-27 15:26   ` Chih-Min Chao
2019-09-10 13:43   ` Palmer Dabbelt
2019-08-23 23:37 ` [Qemu-devel] [PATCH v1 02/28] target/riscv: Add the virtulisation mode Alistair Francis
2019-08-27 15:44   ` [Qemu-devel] [Qemu-riscv] " Chih-Min Chao
2019-08-28  0:08     ` Alistair Francis
2019-09-10 13:44   ` [Qemu-devel] " Palmer Dabbelt
2019-09-16 15:57     ` Alistair Francis
2019-08-23 23:37 ` [Qemu-devel] [PATCH v1 03/28] target/riscv: Add the force HS exception mode Alistair Francis
2019-08-27 15:46   ` Chih-Min Chao
2019-09-10 14:48   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 04/28] target/riscv: Fix CSR perm checking for HS mode Alistair Francis
2019-09-10 14:48   ` Palmer Dabbelt
2019-10-16 20:56     ` Alistair Francis
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 05/28] target/riscv: Add the Hypervisor CSRs to CPUState Alistair Francis
2019-08-27 15:50   ` [Qemu-devel] [Qemu-riscv] " Chih-Min Chao
2019-09-10 14:48   ` [Qemu-devel] " Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 06/28] target/riscv: Print priv and virt in disas log Alistair Francis
2019-09-10 14:48   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 07/28] target/riscv: Dump Hypervisor registers if enabled Alistair Francis
2019-09-10 14:48   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 08/28] target/riscv: Add Hypervisor CSR access functions Alistair Francis
2019-09-10 14:48   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 09/28] target/riscv: Add Hypervisor virtual CSRs accesses Alistair Francis
2019-09-10 14:48   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 10/28] target/riscv: Convert mie and mstatus to pointers Alistair Francis
2019-09-11  8:24   ` Palmer Dabbelt
2019-09-11 14:54     ` [Qemu-devel] [Qemu-riscv] " Jonathan Behrens
2019-09-17 23:33       ` Alistair Francis
2019-09-18  1:59         ` Jonathan Behrens
2019-09-18 23:47           ` Alistair Francis
2019-09-19 14:50             ` Richard Henderson [this message]
2019-09-19 16:58               ` Jonathan Behrens
2019-10-25 20:28                 ` Alistair Francis
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 11/28] target/riscv: Add background register swapping function Alistair Francis
2019-09-11 14:17   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 12/28] target/riscv: Add support for virtual interrupt setting Alistair Francis
2019-09-14 20:30   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 13/28] target/ricsv: Flush the TLB on virtulisation mode changes Alistair Francis
2019-09-14 20:30   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 14/28] target/riscv: Generate illegal instruction on WFI when V=1 Alistair Francis
2019-09-14 20:30   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 15/28] riscv: plic: Always set sip.SEIP bit for HS Alistair Francis
2019-09-14 20:32   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 16/28] target/riscv: Add hypvervisor trap support Alistair Francis
2019-09-20 14:01   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 17/28] target/riscv: Add Hypervisor trap return support Alistair Francis
2019-10-01 18:33   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 18/28] target/riscv: Add hfence instructions Alistair Francis
2019-10-01 18:34   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 19/28] target/riscv: Disable guest FP support based on virtual status Alistair Francis
2019-10-01 18:34   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 20/28] target/riscv: Mark both sstatus and vsstatus as dirty Alistair Francis
2019-10-01 18:34   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 21/28] target/riscv: Respect MPRV and SPRV for floating point ops Alistair Francis
2019-10-02 23:52   ` Palmer Dabbelt
2019-10-16 21:01     ` Alistair Francis
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 22/28] target/riscv: Allow specifying MMU stage Alistair Francis
2019-10-03 15:53   ` Palmer Dabbelt
2019-10-07 18:05     ` Alistair Francis
2019-10-16 19:02       ` Palmer Dabbelt
2019-10-16 21:25         ` Alistair Francis
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 23/28] target/riscv: Allow specifying number of MMU stages Alistair Francis
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 24/28] target/riscv: Implement second stage MMU Alistair Francis
2019-10-07 16:15   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 25/28] target/riscv: Call the second stage MMU in virtualisation mode Alistair Francis
2019-10-08 17:54   ` Palmer Dabbelt
2019-08-23 23:38 ` [Qemu-devel] [PATCH v1 26/28] target/riscv: Add support for the 32-bit MSTATUSH CSR Alistair Francis
2019-10-08 18:36   ` Palmer Dabbelt
2019-08-23 23:39 ` [Qemu-devel] [PATCH v1 27/28] target/riscv: Add the MSTATUS_MPV_ISSET helper macro Alistair Francis
2019-10-08 18:36   ` Palmer Dabbelt
2019-10-16 21:14     ` Alistair Francis
2019-08-23 23:39 ` [Qemu-devel] [PATCH v1 28/28] target/riscv: Allow enabling the Hypervisor extension Alistair Francis
2019-10-08 18:53   ` Palmer Dabbelt

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