plat/kvm/x86: Add architecture specific post-EFI stub

Implement a stub that comes after the architecture generic EFI stub
calls the routine that exits `Boot Services`.

This is supposed to finish the architecture specific setupin order
to be able to have a Unikraft valid initial environment state before
`_ukplat_entry` is execited.

Thus, begin by disabling the `Interrupt Flag`, updating the root of
the page tables with our in-image static page tables, unmask the
legacy `8259 PIC`, since, at this point, we do not have `I/O APIC`
support, disable the `LAPIC Timer` initially setup by `UEFI`, set the
legacy shared PCI IRQ's as level triggered since UEFI does not do it
for us (unless we boot in `CSM`) and we do not, at this moment have a
proper IRQ subsystem and, finally, jump to `lcpu_start64` with the
entry function as `_ukplat_entry` and a statically allocated
page-sized stack.

Signed-off-by: Sergiu Moga <sergiu.moga@protonmail.com>
Reviewed-by: Michalis Pappas <michalis@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #909

diff --git a/plat/kvm/x86/efi_x86.c b/plat/kvm/x86/efi_x86.c
new file mode 100644 (file)
index 0000000..21e57f7
--- /dev/null
+++ b/plat/kvm/x86/efi_x86.c
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/* Copyright (c) 2023, Unikraft GmbH and The Unikraft Authors.
+ * Licensed under the BSD-3-Clause License (the "License").
+ * You may not use this file except in compliance with the License.
+ */
+#include <kvm/efi.h>
+#include <uk/arch/paging.h>
+#include <uk/plat/common/bootinfo.h>
+#include <uk/plat/lcpu.h>
+#include <x86/apic_defs.h>
+#include <x86/cpu.h>
+
+/* Slave Controller Edge/Level Triggered Register */
+#define PIC2_ELCR2                                     0x4D1
+#define PIC2_ELCR2_IRQ11_ECL                           (1 << 3)
+#define PIC2_ELCR2_IRQ10_ECL                           (1 << 2)
+
+/* Initial Count Register (for Timer) */
+#define LAPIC_TMICT                                    0xFEE00380
+
+/* Master/Slave PIC Data Registers */
+#define PIC1_DATA                                      0x21
+#define PIC1_DATA_DEFAULT_MASK                         0xB8
+#define PIC2_DATA                                      0xA1
+#define PIC2_DATA_DEFAULT_MASK                         0x8E
+
+extern void lcpu_start64(void *, void *) __noreturn;
+extern void _ukplat_entry(void *, void *);
+extern void *x86_bpt_pml4;
+
+static __u8 __align(16) uk_efi_bootstack[__PAGE_SIZE];
+
+static struct {
+       void *entry_fn;
+       void *bootstack;
+} uk_efi_boot_startup_args;
+
+/* Unless UEFI CSM (now dropped from the specification) is activated, our PIC's
+ * are masked
+ */
+static inline void unmask_8259_pic(void)
+{
+       outb(PIC1_DATA, PIC1_DATA_DEFAULT_MASK);
+       outb(PIC2_DATA, PIC2_DATA_DEFAULT_MASK);
+}
+
+/* UEFI enables the LAPIC Timer to run periodic routines, usually at 10KHz */
+static inline void lapic_timer_disable(void)
+{
+       volatile __u32 *lapic_tmict = (volatile __u32 *)LAPIC_TMICT;
+       __u32 eax, edx;
+
+       /* Check if APIC is active */
+       rdmsr(APIC_MSR_BASE, &eax, &edx);
+       if (unlikely(!(eax & APIC_BASE_EN)))
+               return;
+
+       /* Zero-ing out this register disables the LAPIC Timer */
+       *lapic_tmict = 0x0;
+}
+
+/* Unless UEFI CSM (now dropped from the specification) is activated, our PIC's
+ * are masked and their interrupts mode are not configured.
+ * TODO: Until we have a proper IRQ subsystem to transparently set IRQ type when
+ * registering an IRQ, set the known PIIX/PIIX3 shared PCI IRQ's as
+ * level-triggered
+ */
+static inline void pic_8259_elcr2_level_irq10_11(void)
+{
+       outb(PIC2_ELCR2, PIC2_ELCR2_IRQ11_ECL | PIC2_ELCR2_IRQ10_ECL);
+}
+
+void __noreturn uk_efi_jmp_to_kern()
+{
+       struct ukplat_bootinfo *bi = ukplat_bootinfo_get();
+
+       if (unlikely(!bi))
+               ukplat_crash();
+
+       uk_efi_boot_startup_args.entry_fn = &_ukplat_entry;
+       uk_efi_boot_startup_args.bootstack = uk_efi_bootstack + __PAGE_SIZE;
+
+       ukplat_lcpu_disable_irq();
+       ukarch_pt_write_base((__paddr_t)&x86_bpt_pml4);
+       unmask_8259_pic();
+       lapic_timer_disable();
+       pic_8259_elcr2_level_irq10_11();
+       lcpu_start64(&uk_efi_boot_startup_args, bi);
+}