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

Andre Przywara
2021-02-18T16:15:01Z

On Fri, 12 Feb 2021 11:27:59 +0000
Alexandru Elisei <alexandru.elisei@arm.com> wrote:

Hi Alex,

> 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?

Wading through the swamp of the git history it looks like failure is
intentional, it should be used together with --debug-ioport, to trigger
that print there.

> - 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?

I think you are right, we should print something here.

Cheers,
Andre

> > -
> > -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);