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Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lChJg-00085n-7A; Thu, 18 Feb 2021 11:17:52 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lChJd-00085N-MU for linux-arm-kernel@lists.infradead.org; Thu, 18 Feb 2021 11:17:50 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F1C961042; Thu, 18 Feb 2021 03:17:43 -0800 (PST) Received: from [192.168.0.110] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0029F3F73D; Thu, 18 Feb 2021 03:17:42 -0800 (PST) Subject: Re: [PATCH kvmtool 06/21] hw/i8042: Refactor trap handler To: Andre Przywara References: <20201210142908.169597-1-andre.przywara@arm.com> <20201210142908.169597-7-andre.przywara@arm.com> <288df0e8-997c-7691-2dda-017876dba3f4@arm.com> <20210218103425.26a27000@slackpad.fritz.box> From: Alexandru Elisei Message-ID: <5d2d7233-46f6-3056-e2b2-813a3fc56d88@arm.com> Date: Thu, 18 Feb 2021 11:17:58 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210218103425.26a27000@slackpad.fritz.box> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210218_061749_888141_E3DE4843 X-CRM114-Status: GOOD ( 25.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, Marc Zyngier , Julien Thierry , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Andre, On 2/18/21 10:34 AM, Andre Przywara wrote: > On Thu, 11 Feb 2021 17:23:13 +0000 > Alexandru Elisei wrote: > >> Hi Andre, >> >> On 12/10/20 2:28 PM, Andre Przywara wrote: >>> With the planned retirement of the special ioport emulation code, we >>> need to provide an emulation function compatible with the MMIO >>> prototype. >>> >>> Adjust the trap handler to use that new function, and provide shims to >>> implement the old ioport interface, for now. >>> >>> Signed-off-by: Andre Przywara >>> --- >>> hw/i8042.c | 68 +++++++++++++++++++++++++++--------------------------- >>> 1 file changed, 34 insertions(+), 34 deletions(-) >>> >>> diff --git a/hw/i8042.c b/hw/i8042.c >>> index 36ee183f..eb1f9d28 100644 >>> --- a/hw/i8042.c >>> +++ b/hw/i8042.c >>> @@ -292,52 +292,52 @@ static void kbd_reset(void) >>> }; >>> } >>> >>> -/* >>> - * Called when the OS has written to one of the keyboard's ports (0x60 or 0x64) >>> - */ >>> -static bool kbd_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size) >>> +static void kbd_io(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len, >>> + u8 is_write, void *ptr) >>> { >>> - switch (port) { >>> - case I8042_COMMAND_REG: { >>> - u8 value = kbd_read_status(); >>> - ioport__write8(data, value); >>> + u8 value; >>> + >>> + if (is_write) >>> + value = ioport__read8(data); >>> + >>> + switch (addr) { >>> + case I8042_COMMAND_REG: >>> + if (is_write) >>> + kbd_write_command(vcpu->kvm, value); >>> + else >>> + value = kbd_read_status(); >>> break; >>> - } >>> - case I8042_DATA_REG: { >>> - u8 value = kbd_read_data(); >>> - ioport__write8(data, value); >>> + case I8042_DATA_REG: >>> + if (is_write) >>> + kbd_write_data(value); >>> + else >>> + value = kbd_read_data(); >>> break; >>> - } >>> - case I8042_PORT_B_REG: { >>> - ioport__write8(data, 0x20); >>> + case I8042_PORT_B_REG: >>> + if (!is_write) >>> + value = 0x20; >>> break; >>> - } >>> default: >>> - return false; >>> + return; >> Any particular reason for removing the false return value? I don't see it >> mentioned in the commit message. Otherwise this is identical to the two functions >> it replaces. > Because the MMIO handler prototype is void, in contrast to the PIO one. > Since on returning "false" we only seem to panic kvmtool, this is of > quite limited use, I'd say. Actually, in ioport.c::kvm__emulate_io(), if kvm->cfg.ioport_debug is true, it will print an error and then panic in kvm_cpu__start(); otherwise the error is silently ignored. serial.c is another device where an unknown register returns false. In rtc.c, the unknown register is ignored. cfi_flash.c prints debugging information. So I guess kvmtool implements all possible methods of handling an unknown register *at the same time*, so it's up to you how you want to handle it. >>> } >>> >>> + if (!is_write) >>> + ioport__write8(data, value); >>> +} >>> + >>> +/* >>> + * Called when the OS has written to one of the keyboard's ports (0x60 or 0x64) >>> + */ >>> +static bool kbd_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size) >>> +{ >>> + kbd_io(vcpu, port, data, size, false, NULL); >> is_write is an u8, not a bool. > Right, will fix this. > >> I never could wrap my head around the ioport convention of "in" (read) and "out" >> (write). To be honest, changing is_write changed to an enum so it's crystal clear >> what is happening would help with that a lot, but I guess that's a separate patch. > "in" and "out" are the x86 assembly mnemonics, but it's indeed > confusing, because the device side has a different view (CPU "in" means > pushing data "out" of the device). I usually look at the code to see > what it's actually meant to do. > So yeah, I feel like a lot of those device emulations could use > some update. but that's indeed something for another day. Agreed. Thanks, Alex > > Cheers, > Andre > >>> + >>> return true; >>> } >>> >>> static bool kbd_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size) >>> { >>> - switch (port) { >>> - case I8042_COMMAND_REG: { >>> - u8 value = ioport__read8(data); >>> - kbd_write_command(vcpu->kvm, value); >>> - break; >>> - } >>> - case I8042_DATA_REG: { >>> - u8 value = ioport__read8(data); >>> - kbd_write_data(value); >>> - break; >>> - } >>> - case I8042_PORT_B_REG: { >>> - break; >>> - } >>> - default: >>> - return false; >>> - } >>> + kbd_io(vcpu, port, data, size, true, NULL); >>> >>> return true; >>> } _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel