Merge branch 'xenfv-kvm-15' of git://git.infradead.org/users/dwmw2/qemu into HEAD

This adds support for emulating Xen under Linux/KVM, based on kernel
patches which have been present since Linux v5.12. As with the kernel
support, it's derived from work started by João Martins of Oracle in
2018.

This series just adds the basic platform support — CPUID, hypercalls,
event channels, a stub of XenStore.

A full single-tenant internal implementation of XenStore, and patches
to make QEMU's Xen PV drivers work with this Xen emulation, are waiting
in the wings to be submitted in a follow-on patch series.

As noted in the documentation, it's enabled by setting the xen-version
property on the KVM accelerator, e.g.:

 qemu-system-x86_64 -serial mon:stdio -M q35 -display none -m 1G -smp 2 \
    -accel kvm,xen-version=0x4000e,kernel-irqchip=split \
    -kernel vmlinuz-6.0.7-301.fc37.x86_64 \
    -append "console=ttyS0 root=/dev/sda1" \
    -drive file=/var/lib/libvirt/images/fedora28.qcow2,if=none,id=disk \
    -device ahci,id=ahci -device ide-hd,drive=disk,bus=ahci.0

Even before this was merged, we've already been using it to find and fix
bugs in the Linux kernel Xen guest support:

https://lore.kernel.org/all/4bffa69a949bfdc92c4a18e5a1c3cbb3b94a0d32.camel@infradead.org/
https://lore.kernel.org/all/871qnunycr.ffs@tglx/

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 22 insertions, 4 deletions

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 48be7a1c23..a56b10b2fb 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -61,10 +61,15 @@
 #include CONFIG_DEVICES
 #include "kvm/kvm_i386.h"
 
+#ifdef CONFIG_XEN_EMU
+#include "hw/xen/xen.h"
+#include "hw/i386/kvm/xen_evtchn.h"
+#endif
+
 /* Physical Address of PVH entry point read from kernel ELF NOTE */
 static size_t pvh_start_addr;
 
-inline void init_topo_info(X86CPUTopoInfo *topo_info,
+static void init_topo_info(X86CPUTopoInfo *topo_info,
                            const X86MachineState *x86ms)
 {
     MachineState *ms = MACHINE(x86ms);
@@ -150,17 +155,19 @@ void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)
     }
 }
 
-void x86_rtc_set_cpus_count(ISADevice *rtc, uint16_t cpus_count)
+void x86_rtc_set_cpus_count(ISADevice *s, uint16_t cpus_count)
 {
+    MC146818RtcState *rtc = MC146818_RTC(s);
+
     if (cpus_count > 0xff) {
         /*
          * If the number of CPUs can't be represented in 8 bits, the
          * BIOS must use "FW_CFG_NB_CPUS". Set RTC field to 0 just
          * to make old BIOSes fail more predictably.
          */
-        rtc_set_memory(rtc, 0x5f, 0);
+        mc146818rtc_set_cmos_data(rtc, 0x5f, 0);
     } else {
-        rtc_set_memory(rtc, 0x5f, cpus_count - 1);
+        mc146818rtc_set_cmos_data(rtc, 0x5f, cpus_count - 1);
     }
 }
 
@@ -608,6 +615,17 @@ void gsi_handler(void *opaque, int n, int level)
         }
         /* fall through */
     case ISA_NUM_IRQS ... IOAPIC_NUM_PINS - 1:
+#ifdef CONFIG_XEN_EMU
+        /*
+         * Xen delivers the GSI to the Legacy PIC (not that Legacy PIC
+         * routing actually works properly under Xen). And then to
+         * *either* the PIRQ handling or the I/OAPIC depending on
+         * whether the former wants it.
+         */
+        if (xen_mode == XEN_EMULATE && xen_evtchn_set_gsi(n, level)) {
+            break;
+        }
+#endif
         qemu_set_irq(s->ioapic_irq[n], level);
         break;
     case IO_APIC_SECONDARY_IRQBASE