From c565776195f2f2b62427af07f6b1a9b7670cbc1f Mon Sep 17 00:00:00 2001
From: Wei Hu <whu@FreeBSD.org>
Date: Thu, 30 Jul 2020 07:26:11 +0000
Subject: [PATCH] Prevent framebuffer mmio space from being allocated to other
 devices on HyperV.

On Gen2 VMs, Hyper-V provides mmio space for framebuffer.
This mmio address range is not useable for other PCI devices.
Currently only efifb driver is using this range without reserving
it from system.
Therefore, vmbus driver reserves it before any other PCI device
drivers start to request mmio addresses.

PR:		222996
Submitted by:	weh@microsoft.com
Reported by:	dmitry_kuleshov@ukr.net
Reviewed by:	decui@microsoft.com
Sponsored by:	Microsoft
---
 sys/dev/hyperv/vmbus/vmbus.c | 57 ++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/sys/dev/hyperv/vmbus/vmbus.c b/sys/dev/hyperv/vmbus/vmbus.c
index 9d4f5e77fa97..38e9cd7b4c26 100644
--- a/sys/dev/hyperv/vmbus/vmbus.c
+++ b/sys/dev/hyperv/vmbus/vmbus.c
@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/bus.h>
 #include <sys/kernel.h>
+#include <sys/linker.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/module.h>
@@ -46,6 +47,7 @@ __FBSDID("$FreeBSD$");
 
 #include <machine/bus.h>
 #include <machine/intr_machdep.h>
+#include <machine/metadata.h>
 #include <machine/md_var.h>
 #include <machine/resource.h>
 #include <x86/include/apicvar.h>
@@ -1332,12 +1334,66 @@ vmbus_get_mmio_res(device_t dev)
 	vmbus_get_mmio_res_pass(dev, parse_32);
 }
 
+/*
+ * On Gen2 VMs, Hyper-V provides mmio space for framebuffer.
+ * This mmio address range is not useable for other PCI devices.
+ * Currently only efifb driver is using this range without reserving
+ * it from system.
+ * Therefore, vmbus driver reserves it before any other PCI device
+ * drivers start to request mmio addresses.
+ */
+static struct resource *hv_fb_res;
+
+static void
+vmbus_fb_mmio_res(device_t dev)
+{
+	struct efi_fb *efifb;
+	caddr_t kmdp;
+
+	struct vmbus_softc *sc = device_get_softc(dev);
+	int rid = 0;
+
+	kmdp = preload_search_by_type("elf kernel");
+	if (kmdp == NULL)
+		kmdp = preload_search_by_type("elf64 kernel");
+	efifb = (struct efi_fb *)preload_search_info(kmdp,
+	    MODINFO_METADATA | MODINFOMD_EFI_FB);
+	if (efifb == NULL) {
+		if (bootverbose)
+			device_printf(dev,
+			    "fb has no preloaded kernel efi information\n");
+		/* We are on Gen1 VM, just return. */
+		return;
+	} else {
+		if (bootverbose)
+			device_printf(dev,
+			    "efifb: fb_addr: %#jx, size: %#jx, "
+			    "actual size needed: 0x%x\n",
+			    efifb->fb_addr, efifb->fb_size,
+			    (int) efifb->fb_height * efifb->fb_width);
+	}
+
+	hv_fb_res = pcib_host_res_alloc(&sc->vmbus_mmio_res, dev,
+	    SYS_RES_MEMORY, &rid,
+	    efifb->fb_addr, efifb->fb_addr + efifb->fb_size, efifb->fb_size,
+	    RF_ACTIVE | rman_make_alignment_flags(PAGE_SIZE));
+
+	if (hv_fb_res && bootverbose)
+		device_printf(dev,
+		    "successfully reserved memory for framebuffer "
+		    "starting at %#jx, size %#jx\n",
+		    efifb->fb_addr, efifb->fb_size);
+}
+
 static void
 vmbus_free_mmio_res(device_t dev)
 {
 	struct vmbus_softc *sc = device_get_softc(dev);
 
 	pcib_host_res_free(dev, &sc->vmbus_mmio_res);
+
+	if (hv_fb_res)
+		hv_fb_res = NULL;
 }
 #endif	/* NEW_PCIB */
 
@@ -1387,6 +1443,7 @@ vmbus_doattach(struct vmbus_softc *sc)
 
 #ifdef NEW_PCIB
 	vmbus_get_mmio_res(sc->vmbus_dev);
+	vmbus_fb_mmio_res(sc->vmbus_dev);
 #endif
 
 	sc->vmbus_flags |= VMBUS_FLAG_ATTACHED;