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Fri, 08 Aug 2025 09:11:18 -0700 (PDT) Received: from [192.168.1.87] ([38.41.223.211]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-76bcceab691sm20638770b3a.55.2025.08.08.09.11.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Aug 2025 09:11:17 -0700 (PDT) Message-ID: <6190716c-09da-4abe-94e5-2b713855f0e9@linaro.org> Date: Fri, 8 Aug 2025 09:11:17 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] gdbstub/aarch64: add CurrentEL register To: Manos Pitsidianakis , Peter Maydell Cc: qemu-devel@nongnu.org, =?UTF-8?Q?Alex_Benn=C3=A9e?= , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Gustavo Romero , Richard Henderson , qemu-arm@nongnu.org References: <20250808-gdbstub-aarch64-pstate-regs-v1-0-14ba70be1b3d@linaro.org> <20250808-gdbstub-aarch64-pstate-regs-v1-1-14ba70be1b3d@linaro.org> Content-Language: en-US From: Pierrick Bouvier In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::431; envelope-from=pierrick.bouvier@linaro.org; helo=mail-pf1-x431.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 8/8/25 5:26 AM, Manos Pitsidianakis wrote: > On Fri, Aug 8, 2025 at 3:21 PM Peter Maydell wrote: >> >> On Fri, 8 Aug 2025 at 12:30, Manos Pitsidianakis >> wrote: >>> >>> Signed-off-by: Manos Pitsidianakis >>> --- >>> gdb-xml/aarch64-core.xml | 5 +++++ >>> target/arm/cpu.h | 1 + >>> target/arm/gdbstub64.c | 6 ++++++ >>> 3 files changed, 12 insertions(+) >>> >>> diff --git a/gdb-xml/aarch64-core.xml b/gdb-xml/aarch64-core.xml >>> index b8046510b9a085d30463d37b3ecc8d435f5fb7a4..19ad743dc5607b4021fb795bfb9b8e9cf0adef68 100644 >>> --- a/gdb-xml/aarch64-core.xml >>> +++ b/gdb-xml/aarch64-core.xml >>> @@ -91,4 +91,9 @@ >>> >>> >>> >>> + >>> + >>> + >>> + >>> + >>> >>> diff --git a/target/arm/cpu.h b/target/arm/cpu.h >>> index dc9b6dce4c92297b2636d0d7c0dce580f1806d5b..c3070cd9863381fac40f5640e0a7a84dfa1c6e06 100644 >>> --- a/target/arm/cpu.h >>> +++ b/target/arm/cpu.h >>> @@ -1473,6 +1473,7 @@ void pmu_init(ARMCPU *cpu); >>> * AArch32 mode SPSRs are basically CPSR-format. >>> */ >>> #define PSTATE_SP (1U) >>> +#define PSTATE_EL (3U << 2) >>> #define PSTATE_M (0xFU) >>> #define PSTATE_nRW (1U << 4) >>> #define PSTATE_F (1U << 6) >>> diff --git a/target/arm/gdbstub64.c b/target/arm/gdbstub64.c >>> index 08e28585396816ab90d6d8e460ff8171892fe8da..16b564e1a970cb5e854a705619f71ffc61545a73 100644 >>> --- a/target/arm/gdbstub64.c >>> +++ b/target/arm/gdbstub64.c >>> @@ -48,6 +48,9 @@ int aarch64_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n) >>> return gdb_get_reg64(mem_buf, env->pc); >>> case 33: >>> return gdb_get_reg32(mem_buf, pstate_read(env)); >>> + case 34: >>> + /* CurrentEL */ >>> + return gdb_get_reg64(mem_buf, env->pstate & PSTATE_EL); >>> } >> >> The debugger already has this information in the 'cpsr' >> register, so it could implement convenience views of >> the subfields itself if it liked. > > Yep, but consider: it is a register, architecturally, so it's nice to > include it for consistency. It's redundant only because gdb has cpsr > which is not a register. So this is about more about being technically > correct than correcting an actual problem. > I agree with Manos on this. As mentioned on a previous thread, cpsr is not even supposed to exist for aarch64. So adding architecturally defined registers, even if data is redundant with cpsr, should not be a problem. I'm sure gdb folks can understand this too. > >> >> If we're going to do this I would prefer it to be because >> we've gained some consensus with e.g. the gdb maintainers >> that this is the "preferred" way to expose the CPU state. >> The XML config stuff lets us do it in our own way if we >> want to, but I think there is value in consistency across >> stubs here. > > I plan to upstream the XML patches to gdb as well, separately. But > since we use custom target xml it's not like we depend on gdb to > change it. > >> >> thanks >> -- PMM