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bhyve: allocate guest memory for graphics stolen memory

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The graphics stolen memory is only GPU accessible. So, we don't have to
copy any data to it as the guest will be unable to access it anyway. We
just have to allocate and reserve some memory. That's done by adding an
E820 entry for the graphics stolen memory. The guest firmware will pick
up the E820 and reserve this range.

Note that we try to reuse the host address as Intel states that newer
Tiger Lake platforms need this [1].

[1]
e28d6fbfdf/devicemodel/hw/pci/passthrough.c (L626-L629)

Reviewed by:		markj
MFC after:		1 week
Sponsored by:		Beckhoff Automation GmbH & Co. KG
Differential Revision:	https://reviews.freebsd.org/D40059
This commit is contained in:
Corvin Köhne 2023-05-11 11:10:07 +02:00
parent 4a9bf50f40
commit 1bd361eea2
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GPG Key ID: D854DA56315E026A
1 changed files with 62 additions and 2 deletions
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64
usr.sbin/bhyve/pci_gvt-d.c
View File

@ -8,17 +8,24 @@
#include <sys/types.h>
#include <sys/sysctl.h>
#include <err.h>
#include <dev/pci/pcireg.h>
#include <err.h>
#include <errno.h>
#include "e820.h"
#include "pci_gvt-d-opregion.h"
#include "pci_passthru.h"
#define KB (1024UL)
#define MB (1024 * KB)
#define GB (1024 * MB)
#define PCI_VENDOR_INTEL 0x8086
#define PCIM_BDSM_GSM_ALIGNMENT \
0x00100000 /* Graphics Stolen Memory is 1 MB aligned */
#define GVT_D_MAP_GSM 0
static int
@ -41,6 +48,27 @@ gvt_d_probe(struct pci_devinst *const pi)
return (0);
}
static vm_paddr_t
gvt_d_alloc_mmio_memory(const vm_paddr_t host_address, const vm_paddr_t length,
const vm_paddr_t alignment, const enum e820_memory_type type)
{
vm_paddr_t address;
/* Try to reuse host address. */
address = e820_alloc(host_address, length, E820_ALIGNMENT_NONE, type,
E820_ALLOCATE_SPECIFIC);
if (address != 0) {
return (address);
}
/*
* We're not able to reuse the host address. Fall back to the highest usable
* address below 4 GB.
*/
return (
e820_alloc(4 * GB, length, alignment, type, E820_ALLOCATE_HIGHEST));
}
/*
* Note that the graphics stolen memory is somehow confusing. On the one hand
* the Intel Open Source HD Graphics Programmers' Reference Manual states that
@ -95,6 +123,38 @@ gvt_d_setup_gsm(struct pci_devinst *const pi)
return (-1);
}
gsm->hva = NULL; /* unused */
gsm->gva = NULL; /* unused */
gsm->gpa = gvt_d_alloc_mmio_memory(gsm->hpa, gsm->len,
PCIM_BDSM_GSM_ALIGNMENT, E820_TYPE_RESERVED);
if (gsm->gpa == 0) {
warnx(
"%s: Unable to add Graphics Stolen Memory to E820 table (hpa 0x%lx len 0x%lx)",
__func__, gsm->hpa, gsm->len);
e820_dump_table();
return (-1);
}
if (gsm->gpa != gsm->hpa) {
/*
* ACRN source code implies that graphics driver for newer Intel
* platforms like Tiger Lake will read the Graphics Stolen Memory
* address from an MMIO register. We have three options to solve this
* issue:
* 1. Patch the value in the MMIO register
* This could have unintended side effects. Without any
* documentation how this register is used by the GPU, don't do
* it.
* 2. Trap the MMIO register
* It's not possible to trap a single MMIO register. We need to
* trap a whole page. Trapping a bunch of MMIO register could
* degrade the performance noticeably. We have to test it.
* 3. Use an 1:1 host to guest mapping
* Maybe not always possible. As far as we know, no supported
* platform requires a 1:1 mapping. For that reason, just log a
* warning.
*/
warnx(
"Warning: Unable to reuse host address of Graphics Stolen Memory. GPU passthrough might not work properly.");
}
return (0);
}