| Message ID | TY0PR0101MB42850337F8917D1F514107FBA4D52@TY0PR0101MB4285.apcprd01.prod.exchangelabs.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | hw/intc/ioapic: Delete a wrong IRQ redirection on I/O APIC | expand |
On Tue, Jun 25, 2024 at 2:03 PM TaiseiIto <taisei1212@outlook.jp> wrote: > Before this commit, interruptions from i8254 which should be sent to IRQ0 > were sent to IRQ2. After this commit, these are correctly sent to IRQ0. When > I had an HPET timer generate interruptions once per second to test an HPET > driver in my operating system on QEMU, I observed more frequent > interruptions than I configured on the HPET timer. I investigated the cause > and found that not only interruptions from HPET but also interruptions from > i8254 were sent to IRQ2 because of a redirection from IRQ0 to IRQ2. This > redirection is added in hw/apic.c at commit > 16b29ae1807b024bd5052301550f5d47dae958a2 but this redirection caused wrong > interruptions. So I deleted the redirection. Finally, I confirmed there is > no problem on 'make check' results and that interruptions from i8254 and > interruptions from HPET are correclty sent to IRQ0 and IRQ2 respectively. Hi, did you set the legacy replacement route bit on the HPET? My understanding is that: - if you enable legacy-replacement routing, the HPET will take care of dropping all i8254 interrupts - if you disable legacy-replacement routing, the i8254 will still generate interrupts on ISA IRQ 0. If you then enable the IO-APIC and program the routes according to the ACPI MADT table, the interrupt from the i8254 (ISA IRQ 0) will be redirected to the IO-APIC's GSI2. So the solutions would be one of the following if you use HPET timer 0: - disable the i8254 - enable legacy-replacement routing - mask GSI2 on the IO-APIC and use a different route for the HPET (worse, but should also work) Thanks, Paolo > Signed-off-by: TaiseiIto <taisei1212@outlook.jp> > --- > hw/intc/ioapic.c | 7 ------- > 1 file changed, 7 deletions(-) > > diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c > index 716ffc8bbb..6b630b45ca 100644 > --- a/hw/intc/ioapic.c > +++ b/hw/intc/ioapic.c > @@ -154,15 +154,8 @@ static void ioapic_set_irq(void *opaque, int vector, int level) > { > IOAPICCommonState *s = opaque; > > - /* ISA IRQs map to GSI 1-1 except for IRQ0 which maps > - * to GSI 2. GSI maps to ioapic 1-1. This is not > - * the cleanest way of doing it but it should work. */ > - > trace_ioapic_set_irq(vector, level); > ioapic_stat_update_irq(s, vector, level); > - if (vector == 0) { > - vector = 2; > - } > if (vector < IOAPIC_NUM_PINS) { > uint32_t mask = 1 << vector; > uint64_t entry = s->ioredtbl[vector]; > -- > 2.34.1 >
I tried to enable the legacy replacement routing without the patch. It works correctly. Thanks. Taisei
On Tue, 2024-07-23 at 16:15 +0200, Paolo Bonzini wrote: > On Tue, Jun 25, 2024 at 2:03 PM TaiseiIto <taisei1212@outlook.jp> wrote: > > Before this commit, interruptions from i8254 which should be sent to IRQ0 > > were sent to IRQ2. After this commit, these are correctly sent to IRQ0. When > > I had an HPET timer generate interruptions once per second to test an HPET > > driver in my operating system on QEMU, I observed more frequent > > interruptions than I configured on the HPET timer. I investigated the cause > > and found that not only interruptions from HPET but also interruptions from > > i8254 were sent to IRQ2 because of a redirection from IRQ0 to IRQ2. This > > redirection is added in hw/apic.c at commit > > 16b29ae1807b024bd5052301550f5d47dae958a2 but this redirection caused wrong > > interruptions. So I deleted the redirection. Finally, I confirmed there is > > no problem on 'make check' results and that interruptions from i8254 and > > interruptions from HPET are correclty sent to IRQ0 and IRQ2 respectively. > > Hi, did you set the legacy replacement route bit on the HPET? > > My understanding is that: > - if you enable legacy-replacement routing, the HPET will take care of > dropping all i8254 interrupts > - if you disable legacy-replacement routing, the i8254 will still > generate interrupts on ISA IRQ 0. If you then enable the IO-APIC and > program the routes according to the ACPI MADT table, the interrupt > from the i8254 (ISA IRQ 0) will be redirected to the IO-APIC's GSI2. > > So the solutions would be one of the following if you use HPET timer 0: > - disable the i8254 > - enable legacy-replacement routing > - mask GSI2 on the IO-APIC and use a different route for the HPET > (worse, but should also work) Or we delete the existing hack which redirects IRQ0→IRQ2 in the I/OAPIC and replace it with an IRQ2→IRQ0 hack in gsi_handler(), as seen in https://mail.gnu.org/archive/html/qemu-devel/2023-10/msg06163.html
diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c index 716ffc8bbb..6b630b45ca 100644 --- a/hw/intc/ioapic.c +++ b/hw/intc/ioapic.c @@ -154,15 +154,8 @@ static void ioapic_set_irq(void *opaque, int vector, int level) { IOAPICCommonState *s = opaque; - /* ISA IRQs map to GSI 1-1 except for IRQ0 which maps - * to GSI 2. GSI maps to ioapic 1-1. This is not - * the cleanest way of doing it but it should work. */ - trace_ioapic_set_irq(vector, level); ioapic_stat_update_irq(s, vector, level); - if (vector == 0) { - vector = 2; - } if (vector < IOAPIC_NUM_PINS) { uint32_t mask = 1 << vector; uint64_t entry = s->ioredtbl[vector];
Before this commit, interruptions from i8254 which should be sent to IRQ0 were sent to IRQ2. After this commit, these are correctly sent to IRQ0. When I had an HPET timer generate interruptions once per second to test an HPET driver in my operating system on QEMU, I observed more frequent interruptions than I configured on the HPET timer. I investigated the cause and found that not only interruptions from HPET but also interruptions from i8254 were sent to IRQ2 because of a redirection from IRQ0 to IRQ2. This redirection is added in hw/apic.c at commit 16b29ae1807b024bd5052301550f5d47dae958a2 but this redirection caused wrong interruptions. So I deleted the redirection. Finally, I confirmed there is no problem on 'make check' results and that interruptions from i8254 and interruptions from HPET are correclty sent to IRQ0 and IRQ2 respectively. Signed-off-by: TaiseiIto <taisei1212@outlook.jp> --- hw/intc/ioapic.c | 7 ------- 1 file changed, 7 deletions(-)