Re: [Xen-devel] [Qemu-devel] [PATCH] xen-hvm: stop faking I/O to access PCI config space

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Alexey G [mailto:x1917x@xxxxxxxxx]
> Sent: 03 May 2018 13:41
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; qemu-devel@xxxxxxxxxx; Stefano
> Stabellini <sstabellini@xxxxxxxxxx>; Eduardo Habkost
> <ehabkost@xxxxxxxxxx>; Michael S. Tsirkin <mst@xxxxxxxxxx>; Marcel
> Apfelbaum <marcel@xxxxxxxxxx>; Anthony Perard
> <anthony.perard@xxxxxxxxxx>; Paolo Bonzini <pbonzini@xxxxxxxxxx>;
> Richard Henderson <rth@xxxxxxxxxxx>
> Subject: Re: [Qemu-devel] [PATCH] xen-hvm: stop faking I/O to access PCI
> config space
> 
> On Thu, 3 May 2018 12:18:40 +0100
> Paul Durrant <paul.durrant@xxxxxxxxxx> wrote:
> 
> >This patch removes the current hackery where IOREQ_TYPE_PCI_CONFIG
> >reqyests are handled by faking PIO to 0xcf8 and 0xcfc and replaces it
> >with direct calls to pci_host_config_read/write_common().
> >Doing so necessitates mapping BDFs to PCIDevices but maintaining a
> >simple QLIST in xen_device_realize/unrealize() will suffice.
> >
> >NOTE: whilst config space accesses are currently limited to
> >      PCI_CONFIG_SPACE_SIZE, this patch paves the way to increasing the
> >      limit to PCIE_CONFIG_SPACE_SIZE when Xen gains the ability to
> >      emulate MCFG table accesses.
> >
> >Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> 
> Minor problem here is a possible incompatibility with PCI-PCI bridges
> which we'll need to use eventually for Q35 PT -- IIRC changing secondary
> bus numbers do not cause unrealize/realize pair to be called for
> affected PCI devices. This means that dev_list may contain stale BDF
> information if any related bus number change.

It also means that emulation won't work in general since, unless the devices 
are re-registered with Xen under their new BDFs things are not going to get 
steered correctly. This patch will not change that behaviour so no regression 
is introduced by removing the I/O fakery.

> 
> Anyway, PCI-PCI bridges and their secondary bus numbers must be handled
> specifically, so it can be ignored for now.
> 

As we're discussed before, Xen needs to own the topology so it knows what's 
going on.

> I'll try to reuse this patch for my Xen patch for supporting MMCONFIG
> ioreq forwarding to multiple ioreq servers.
> 

It should be ok (with the increased limit of course).

  Paul

> >--
> >Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> >Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
> >Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> >Cc: Marcel Apfelbaum <marcel@xxxxxxxxxx>
> >Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >Cc: Richard Henderson <rth@xxxxxxxxxxx>
> >Cc: Eduardo Habkost <ehabkost@xxxxxxxxxx>
> >---
> > hw/i386/xen/trace-events |   2 +
> > hw/i386/xen/xen-hvm.c    | 101
> > +++++++++++++++++++++++++++++++++++++---------- 2 files changed,
> 83
> > insertions(+), 20 deletions(-)
> >
> >diff --git a/hw/i386/xen/trace-events b/hw/i386/xen/trace-events
> >index 8dab7bc..f576f1b 100644
> >--- a/hw/i386/xen/trace-events
> >+++ b/hw/i386/xen/trace-events
> >@@ -15,6 +15,8 @@ cpu_ioreq_pio(void *req, uint32_t dir, uint32_t df,
> >uint32_t data_is_ptr, uint64
> > cpu_ioreq_pio_read_reg(void *req, uint64_t data, uint64_t addr,
> > uint32_t size) "I/O=%p pio read reg data=0x%"PRIx64" port=0x%"PRIx64"
> > size=%d" cpu_ioreq_pio_write_reg(void *req, uint64_t data, uint64_t
> > addr, uint32_t size) "I/O=%p pio write reg data=0x%"PRIx64"
> > port=0x%"PRIx64" size=%d" cpu_ioreq_move(void *req, uint32_t dir,
> > uint32_t df, uint32_t data_is_ptr, uint64_t addr, uint64_t data,
> > uint32_t count, uint32_t size) "I/O=%p copy dir=%d df=%d ptr=%d
> > port=0x%"PRIx64" data=0x%"PRIx64" count=%d size=%d"
> >+cpu_ioreq_config_read(void *req, uint32_t sbdf, uint32_t reg,
> >uint32_t size, uint32_t data) "I/O=%p sbdf=0x%x reg=%u size=%u
> >data=0x%x" +cpu_ioreq_config_write(void *req, uint32_t sbdf, uint32_t
> >reg, uint32_t size, uint32_t data) "I/O=%p sbdf=0x%x reg=%u size=%u
> >data=0x%x"
> >
> > # xen-mapcache.c
> > xen_map_cache(uint64_t phys_addr) "want 0x%"PRIx64
> >diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
> >index caa563b..c139d29 100644
> >--- a/hw/i386/xen/xen-hvm.c
> >+++ b/hw/i386/xen/xen-hvm.c
> >@@ -12,6 +12,7 @@
> >
> > #include "cpu.h"
> > #include "hw/pci/pci.h"
> >+#include "hw/pci/pci_host.h"
> > #include "hw/i386/pc.h"
> > #include "hw/i386/apic-msidef.h"
> > #include "hw/xen/xen_common.h"
> >@@ -86,6 +87,12 @@ typedef struct XenPhysmap {
> >     QLIST_ENTRY(XenPhysmap) list;
> > } XenPhysmap;
> >
> >+typedef struct XenPciDevice {
> >+    PCIDevice *pci_dev;
> >+    uint32_t sbdf;
> >+    QLIST_ENTRY(XenPciDevice) entry;
> >+} XenPciDevice;
> >+
> > typedef struct XenIOState {
> >     ioservid_t ioservid;
> >     shared_iopage_t *shared_page;
> >@@ -105,6 +112,7 @@ typedef struct XenIOState {
> >     struct xs_handle *xenstore;
> >     MemoryListener memory_listener;
> >     MemoryListener io_listener;
> >+    QLIST_HEAD(, XenPciDevice) dev_list;
> >     DeviceListener device_listener;
> >     QLIST_HEAD(, XenPhysmap) physmap;
> >     hwaddr free_phys_offset;
> >@@ -569,6 +577,12 @@ static void xen_device_realize(DeviceListener
> >*listener,
> >
> >     if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
> >         PCIDevice *pci_dev = PCI_DEVICE(dev);
> >+        XenPciDevice *xendev = g_new(XenPciDevice, 1);
> >+
> >+        xendev->pci_dev = pci_dev;
> >+        xendev->sbdf = PCI_BUILD_BDF(pci_dev_bus_num(pci_dev),
> >+                                     pci_dev->devfn);
> >+        QLIST_INSERT_HEAD(&state->dev_list, xendev, entry);
> >
> >         xen_map_pcidev(xen_domid, state->ioservid, pci_dev);
> >     }
> >@@ -581,8 +595,17 @@ static void xen_device_unrealize(DeviceListener
> >*listener,
> >
> >     if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
> >         PCIDevice *pci_dev = PCI_DEVICE(dev);
> >+        XenPciDevice *xendev, *next;
> >
> >         xen_unmap_pcidev(xen_domid, state->ioservid, pci_dev);
> >+
> >+        QLIST_FOREACH_SAFE(xendev, &state->dev_list, entry, next) {
> >+            if (xendev->pci_dev == pci_dev) {
> >+                QLIST_REMOVE(xendev, entry);
> >+                g_free(xendev);
> >+                break;
> >+            }
> >+        }
> >     }
> > }
> >
> >@@ -903,6 +926,61 @@ static void cpu_ioreq_move(ioreq_t *req)
> >     }
> > }
> >
> >+static void cpu_ioreq_config(XenIOState *state, ioreq_t *req)
> >+{
> >+    uint32_t sbdf = req->addr >> 32;
> >+    uint32_t reg = req->addr;
> >+    XenPciDevice *xendev;
> >+
> >+    if (req->size > sizeof(uint32_t)) {
> >+        hw_error("PCI config access: bad size (%u)", req->size);
> >+    }
> >+
> >+    QLIST_FOREACH(xendev, &state->dev_list, entry) {
> >+        unsigned int i;
> >+
> >+        if (xendev->sbdf != sbdf) {
> >+            continue;
> >+        }
> >+
> >+        if (req->dir == IOREQ_READ) {
> >+            if (!req->data_is_ptr) {
> >+                req->data = pci_host_config_read_common(
> >+                    xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE,
> >+                    req->size);
> >+                trace_cpu_ioreq_config_read(req, sbdf, reg, req->size,
> >+                                            req->data);
> >+            } else {
> >+                for (i = 0; i < req->count; i++) {
> >+                    uint32_t tmp;
> >+
> >+                    tmp = pci_host_config_read_common(
> >+                        xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE,
> >+                        req->size);
> >+                    write_phys_req_item(req->data, req, i, &tmp);
> >+                }
> >+            }
> >+        } else if (req->dir == IOREQ_WRITE) {
> >+            if (!req->data_is_ptr) {
> >+                trace_cpu_ioreq_config_write(req, sbdf, reg,
> >req->size,
> >+                                             req->data);
> >+                pci_host_config_write_common(
> >+                    xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE,
> >req->data,
> >+                    req->size);
> >+            } else {
> >+                for (i = 0; i < req->count; i++) {
> >+                    uint32_t tmp = 0;
> >+
> >+                    read_phys_req_item(req->data, req, i, &tmp);
> >+                    pci_host_config_write_common(
> >+                        xendev->pci_dev, reg, PCI_CONFIG_SPACE_SIZE,
> >tmp,
> >+                        req->size);
> >+                }
> >+            }
> >+        }
> >+    }
> >+}
> >+
> > static void regs_to_cpu(vmware_regs_t *vmport_regs, ioreq_t *req)
> > {
> >     X86CPU *cpu;
> >@@ -975,27 +1053,9 @@ static void handle_ioreq(XenIOState *state,
> >ioreq_t *req)
> >         case IOREQ_TYPE_INVALIDATE:
> >             xen_invalidate_map_cache();
> >             break;
> >-        case IOREQ_TYPE_PCI_CONFIG: {
> >-            uint32_t sbdf = req->addr >> 32;
> >-            uint32_t val;
> >-
> >-            /* Fake a write to port 0xCF8 so that
> >-             * the config space access will target the
> >-             * correct device model.
> >-             */
> >-            val = (1u << 31) |
> >-                  ((req->addr & 0x0f00) << 16) |
> >-                  ((sbdf & 0xffff) << 8) |
> >-                  (req->addr & 0xfc);
> >-            do_outp(0xcf8, 4, val);
> >-
> >-            /* Now issue the config space access via
> >-             * port 0xCFC
> >-             */
> >-            req->addr = 0xcfc | (req->addr & 0x03);
> >-            cpu_ioreq_pio(req);
> >+        case IOREQ_TYPE_PCI_CONFIG:
> >+            cpu_ioreq_config(state, req);
> >             break;
> >-        }
> >         default:
> >             hw_error("Invalid ioreq type 0x%x\n", req->type);
> >     }
> >@@ -1366,6 +1426,7 @@ void xen_hvm_init(PCMachineState *pcms,
> >MemoryRegion **ram_memory)
> >     memory_listener_register(&state->io_listener, &address_space_io);
> >
> >     state->device_listener = xen_device_listener;
> >+    QLIST_INIT(&state->dev_list);
> >     device_listener_register(&state->device_listener);
> >
> >     /* Initialize backend core & drivers */


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