Re: [PATCH kvmtool 09/21] x86/ioport: Switch to new trap handlers

Alexandru Elisei
2021-02-12T11:28:46Z

Hi Andre,

On 12/10/20 2:28 PM, Andre Przywara wrote:
> Now that the x86 I/O ports have trap handlers adhering to the MMIO fault
> handler prototype, let's switch over to the joint registration routine.
>
> This allows us to get rid of the ioport shim routines.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> x86/ioport.c | 113 ++++++++++++++-------------------------------------
> 1 file changed, 30 insertions(+), 83 deletions(-)
>
> diff --git a/x86/ioport.c b/x86/ioport.c
> index 932da20a..87955da1 100644
> --- a/x86/ioport.c
> +++ b/x86/ioport.c
> @@ -8,16 +8,6 @@ static void dummy_mmio(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len,
> {
> }
>
> -static bool debug_io_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> -{
> - dummy_mmio(vcpu, port, data, size, true, NULL);
> - return 0;
> -}

0 is false in boolean logic, which means that emulation fails according to the
(old) ioport emulation code (ioport.c::kvm__emulate_io()).

So I guess I have a few questions:

- Is this a bug in the emulation code, where the author thought that
debug_io_out() returns an int, and in that case 0 actually means success?

- If writing to the debug port is rightfully considered an error, do we care
enough about it to print something to stdout like kvm__emulate_io() does when
debug_io_out() returns false?

Thanks,

Alex

> -
> -static struct ioport_operations debug_ops = {
> - .io_out = debug_io_out,
> -};
> -
> static void seabios_debug_mmio(struct kvm_cpu *vcpu, u64 addr, u8 *data,
> u32 len, u8 is_write, void *ptr)
> {
> @@ -31,37 +21,6 @@ static void seabios_debug_mmio(struct kvm_cpu *vcpu, u64 addr, u8 *data,
> putchar(ch);
> }
>
> -static bool seabios_debug_io_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> -{
> - seabios_debug_mmio(vcpu, port, data, size, true, NULL);
> - return 0;
> -}
> -
> -static struct ioport_operations seabios_debug_ops = {
> - .io_out = seabios_debug_io_out,
> -};
> -
> -static bool dummy_io_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> -{
> - dummy_mmio(vcpu, port, data, size, false, NULL);
> - return true;
> -}
> -
> -static bool dummy_io_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> -{
> - dummy_mmio(vcpu, port, data, size, true, NULL);
> - return true;
> -}
> -
> -static struct ioport_operations dummy_read_write_ioport_ops = {
> - .io_in = dummy_io_in,
> - .io_out = dummy_io_out,
> -};
> -
> -static struct ioport_operations dummy_write_only_ioport_ops = {
> - .io_out = dummy_io_out,
> -};
> -
> /*
> * The "fast A20 gate"
> */
> @@ -76,17 +35,6 @@ static void ps2_control_mmio(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len,
> ioport__write8(data, 0x02);
> }
>
> -static bool ps2_control_a_io_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> -{
> - ps2_control_mmio(vcpu, port, data, size, false, NULL);
> - return true;
> -}
> -
> -static struct ioport_operations ps2_control_a_ops = {
> - .io_in = ps2_control_a_io_in,
> - .io_out = dummy_io_out,
> -};
> -
> void ioport__map_irq(u8 *irq)
> {
> }
> @@ -98,75 +46,75 @@ static int ioport__setup_arch(struct kvm *kvm)
> /* Legacy ioport setup */
>
> /* 0000 - 001F - DMA1 controller */
> - r = ioport__register(kvm, 0x0000, &dummy_read_write_ioport_ops, 32, NULL);
> + r = kvm__register_pio(kvm, 0x0000, 32, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* 0x0020 - 0x003F - 8259A PIC 1 */
> - r = ioport__register(kvm, 0x0020, &dummy_read_write_ioport_ops, 2, NULL);
> + r = kvm__register_pio(kvm, 0x0020, 2, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* PORT 0040-005F - PIT - PROGRAMMABLE INTERVAL TIMER (8253, 8254) */
> - r = ioport__register(kvm, 0x0040, &dummy_read_write_ioport_ops, 4, NULL);
> + r = kvm__register_pio(kvm, 0x0040, 4, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* 0092 - PS/2 system control port A */
> - r = ioport__register(kvm, 0x0092, &ps2_control_a_ops, 1, NULL);
> + r = kvm__register_pio(kvm, 0x0092, 1, ps2_control_mmio, NULL);
> if (r < 0)
> return r;
>
> /* 0x00A0 - 0x00AF - 8259A PIC 2 */
> - r = ioport__register(kvm, 0x00A0, &dummy_read_write_ioport_ops, 2, NULL);
> + r = kvm__register_pio(kvm, 0x00A0, 2, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* 00C0 - 001F - DMA2 controller */
> - r = ioport__register(kvm, 0x00C0, &dummy_read_write_ioport_ops, 32, NULL);
> + r = kvm__register_pio(kvm, 0x00c0, 32, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* PORT 00E0-00EF are 'motherboard specific' so we use them for our
> internal debugging purposes. */
> - r = ioport__register(kvm, IOPORT_DBG, &debug_ops, 1, NULL);
> + r = kvm__register_pio(kvm, IOPORT_DBG, 1, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* PORT 00ED - DUMMY PORT FOR DELAY??? */
> - r = ioport__register(kvm, 0x00ED, &dummy_write_only_ioport_ops, 1, NULL);
> + r = kvm__register_pio(kvm, 0x00ed, 1, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* 0x00F0 - 0x00FF - Math co-processor */
> - r = ioport__register(kvm, 0x00F0, &dummy_write_only_ioport_ops, 2, NULL);
> + r = kvm__register_pio(kvm, 0x00f0, 2, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* PORT 0278-027A - PARALLEL PRINTER PORT (usually LPT1, sometimes LPT2) */
> - r = ioport__register(kvm, 0x0278, &dummy_read_write_ioport_ops, 3, NULL);
> + r = kvm__register_pio(kvm, 0x0278, 3, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* PORT 0378-037A - PARALLEL PRINTER PORT (usually LPT2, sometimes LPT3) */
> - r = ioport__register(kvm, 0x0378, &dummy_read_write_ioport_ops, 3, NULL);
> + r = kvm__register_pio(kvm, 0x0378, 3, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> /* PORT 03D4-03D5 - COLOR VIDEO - CRT CONTROL REGISTERS */
> - r = ioport__register(kvm, 0x03D4, &dummy_read_write_ioport_ops, 1, NULL);
> + r = kvm__register_pio(kvm, 0x03d4, 1, dummy_mmio, NULL);
> if (r < 0)
> return r;
> - r = ioport__register(kvm, 0x03D5, &dummy_write_only_ioport_ops, 1, NULL);
> + r = kvm__register_pio(kvm, 0x03d5, 1, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> - r = ioport__register(kvm, 0x402, &seabios_debug_ops, 1, NULL);
> + r = kvm__register_pio(kvm, 0x0402, 1, seabios_debug_mmio, NULL);
> if (r < 0)
> return r;
>
> /* 0510 - QEMU BIOS configuration register */
> - r = ioport__register(kvm, 0x510, &dummy_read_write_ioport_ops, 2, NULL);
> + r = kvm__register_pio(kvm, 0x0510, 2, dummy_mmio, NULL);
> if (r < 0)
> return r;
>
> @@ -176,22 +124,21 @@ dev_base_init(ioport__setup_arch);
>
> static int ioport__remove_arch(struct kvm *kvm)
> {
> - ioport__unregister(kvm, 0x510);
> - ioport__unregister(kvm, 0x402);
> - ioport__unregister(kvm, 0x03D5);
> - ioport__unregister(kvm, 0x03D4);
> - ioport__unregister(kvm, 0x0378);
> - ioport__unregister(kvm, 0x0278);
> - ioport__unregister(kvm, 0x00F0);
> - ioport__unregister(kvm, 0x00ED);
> - ioport__unregister(kvm, IOPORT_DBG);
> - ioport__unregister(kvm, 0x00C0);
> - ioport__unregister(kvm, 0x00A0);
> - ioport__unregister(kvm, 0x0092);
> - ioport__unregister(kvm, 0x0040);
> - ioport__unregister(kvm, 0x0020);
> - ioport__unregister(kvm, 0x0000);
> -
> + kvm__deregister_pio(kvm, 0x510);
> + kvm__deregister_pio(kvm, 0x402);
> + kvm__deregister_pio(kvm, 0x3d5);
> + kvm__deregister_pio(kvm, 0x3d4);
> + kvm__deregister_pio(kvm, 0x378);
> + kvm__deregister_pio(kvm, 0x278);
> + kvm__deregister_pio(kvm, 0x0f0);
> + kvm__deregister_pio(kvm, 0x0ed);
> + kvm__deregister_pio(kvm, IOPORT_DBG);
> + kvm__deregister_pio(kvm, 0x0c0);
> + kvm__deregister_pio(kvm, 0x0a0);
> + kvm__deregister_pio(kvm, 0x092);
> + kvm__deregister_pio(kvm, 0x040);
> + kvm__deregister_pio(kvm, 0x020);
> + kvm__deregister_pio(kvm, 0x000);
> return 0;
> }
> dev_base_exit(ioport__remove_arch);