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Re: [Qemu-devel] Xen: enabling emulated MSI injection
From: |
Wei Liu |
Subject: |
Re: [Qemu-devel] Xen: enabling emulated MSI injection |
Date: |
Thu, 26 May 2011 15:35:51 +0800 |
On Thu, May 26, 2011 at 3:21 PM, Jan Kiszka <address@hidden> wrote:
> A cleaner way of hooking into this would be registering on the MSI MMIO
> target region (replacing the APIC). That would give you MSI support as well.
>
> However, KVM has much more complex requirements for MSI handling when
> using the in-kernel irqchip. That's because we need to support, e.g.,
> eventfd-based MSI injection in the hypervisor without looping over QEMU,
> ie. we need to translate a binary event into a MSI address/data tuple.
> This is currently solved a bit too pragmatic in our qemu-kvm tree -
> not mergeable to upstream. So I started working out a better plan,
> partly based on ideas Avi provided.
>
> One element in this concept will be a hook into the MSI delivery path,
> both for events triggered by msi/msix_notify as well as those raised by
> weird DMA (to be architecturally correct). See below for a snapshot
> (depends on other patches). That will obsolete any open-coded hooking
> like this here.
>
> If Xen support is urging, I could try to break out the relevant bits a
> bit earlier. Otherwise I would prefer to postpone the topic by a few
> weeks until we are done with evaluating the concept against KVM's
> requirements so that we can find a truly generic solution.
>
> Jan
>
>
> ------8<-------
>
> diff --git a/hw/apic.c b/hw/apic.c
> index a45b57f..7447d91 100644
> --- a/hw/apic.c
> +++ b/hw/apic.c
> @@ -19,6 +19,7 @@
> #include "hw.h"
> #include "apic.h"
> #include "ioapic.h"
> +#include "msi.h"
> #include "qemu-timer.h"
> #include "host-utils.h"
> #include "sysbus.h"
> @@ -795,7 +796,7 @@ static uint32_t apic_mem_readl(void *opaque,
> target_phys_addr_t addr)
> return val;
> }
>
> -static void apic_send_msi(target_phys_addr_t addr, uint32_t data)
> +void apic_deliver_msi(uint64_t addr, uint32_t data)
> {
> uint8_t dest = (addr & MSI_ADDR_DEST_ID_MASK) >> MSI_ADDR_DEST_ID_SHIFT;
> uint8_t vector = (data & MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT;
> @@ -817,7 +818,9 @@ static void apic_mem_writel(void *opaque,
> target_phys_addr_t addr, uint32_t val)
> * APIC is connected directly to the CPU.
> * Mapping them on the global bus happens to work because
> * MSI registers are reserved in APIC MMIO and vice versa. */
> - apic_send_msi(addr, val);
> + MSIMessage msg = { .address = addr, .data = val };
> +
> + msi_deliver(&msg);
> return;
> }
>
> diff --git a/hw/apic.h b/hw/apic.h
> index c857d52..d0971ae 100644
> --- a/hw/apic.h
> +++ b/hw/apic.h
> @@ -20,6 +20,7 @@ void cpu_set_apic_tpr(DeviceState *s, uint8_t val);
> uint8_t cpu_get_apic_tpr(DeviceState *s);
> void apic_init_reset(DeviceState *s);
> void apic_sipi(DeviceState *s);
> +void apic_deliver_msi(uint64_t addr, uint32_t data);
>
> /* pc.c */
> int cpu_is_bsp(CPUState *env);
> diff --git a/hw/msi.c b/hw/msi.c
> index e111ceb..b88dcc4 100644
> --- a/hw/msi.c
> +++ b/hw/msi.c
> @@ -37,6 +37,14 @@
>
> #define PCI_MSI_VECTORS_MAX 32
>
> +static void msi_unsupported(MSIMessage *msg)
> +{
> + /* If we get here, the board failed to register a delivery handler. */
> + abort();
> +}
> +
> +void (*msi_deliver)(MSIMessage *msg) = msi_unsupported;
> +
> /* If we get rid of cap allocator, we won't need this. */
> static inline uint8_t msi_cap_sizeof(uint16_t flags)
> {
> @@ -361,7 +369,7 @@ void msi_notify(PCIDevice *dev, unsigned int vector)
> "notify vector 0x%x"
> " address: 0x%"PRIx64" data: 0x%"PRIx32"\n",
> vector, msg.address, msg.data);
> - stl_phys(msg.address, msg.data);
> + msi_deliver(&msg);
> }
>
> /* call this function after updating configs by pci_default_write_config().
> */
> diff --git a/hw/msi.h b/hw/msi.h
> index 7a0e76f..ba76eca 100644
> --- a/hw/msi.h
> +++ b/hw/msi.h
> @@ -44,4 +44,6 @@ static inline bool msi_present(const PCIDevice *dev)
> return dev->cap_present & QEMU_PCI_CAP_MSI;
> }
>
> +extern void (*msi_deliver)(MSIMessage *msg);
> +
> #endif /* QEMU_MSI_H */
> diff --git a/hw/msix.c b/hw/msix.c
> index 6e55422..d893f88 100644
> --- a/hw/msix.c
> +++ b/hw/msix.c
> @@ -514,7 +514,7 @@ void msix_notify(PCIDevice *dev, unsigned vector)
>
> msix_message_from_vector(dev, vector, &msg);
>
> - stl_phys(msg.address, msg.data);
> + msi_deliver(&msg);
> }
>
> void msix_reset(PCIDevice *dev)
> diff --git a/hw/pc.c b/hw/pc.c
> index 73398eb..f88ef03 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -24,6 +24,7 @@
> #include "hw.h"
> #include "pc.h"
> #include "apic.h"
> +#include "msi.h"
> #include "fdc.h"
> #include "ide.h"
> #include "pci.h"
> @@ -102,6 +103,15 @@ void isa_irq_handler(void *opaque, int n, int level)
> qemu_set_irq(isa->ioapic[n], level);
> };
>
> +static void pc_msi_deliver(MSIMessage *msg)
> +{
> + if ((msg->address & 0xfff00000) == MSI_ADDR_BASE) {
> + apic_deliver_msi(msg->address, msg->data);
> + } else {
> + stl_phys(msg->address, msg->data);
> + }
> +}
> +
> static void ioport80_write(void *opaque, uint32_t addr, uint32_t data)
> {
> }
> @@ -889,6 +899,7 @@ static DeviceState *apic_init(void *env, uint8_t apic_id)
> on the global memory bus. */
> /* XXX: what if the base changes? */
> sysbus_mmio_map(d, 0, MSI_ADDR_BASE);
> + msi_deliver = pc_msi_deliver;
> apic_mapped = 1;
> }
>
> --
> 1.7.1
>
> --
> Siemens AG, Corporate Technology, CT T DE IT 1
> Corporate Competence Center Embedded Linux
>
Hmm... This patch is just part of GSoC project Virtio on Xen. AFAICS,
this is not so urgent.
I would prefer a cleaner way. A standalone function that doesn't
belong to any QEMU subsystem annoys me. And the hooking looks ugly.
Thanks for your patch, I think we can wait for a better design and
cleaner solution for both Xen and KVM.
--
Best regards
Wei Liu
Twitter: @iliuw
Site: http://liuw.name