On Tue, Aug 1, 2023 at 4:16 AM Daniel Henrique Barboza
<dbarb...@ventanamicro.com> wrote:
>
>
>
> On 7/30/23 22:53, Fei Wu wrote:
> > riscv virt platform's memory started at 0x80000000 and
> > straddled the 4GiB boundary. Curiously enough, this choice
> > of a memory layout will prevent from launching a VM with
> > a bit more than 2000MiB and PCIe pass-thru on an x86 host, due
> > to identity mapping requirements for the MSI doorbell on x86,
> > and these (APIC/IOAPIC) live right below 4GiB.
> >
> > So just split the RAM range into two portions:
> > - 1 GiB range from 0x80000000 to 0xc0000000.
> > - The remainder at 0x100000000
> >
> > ...leaving a hole between the ranges.
>
> I am afraid this breaks some existing distro setups, like Ubuntu. After this
> patch
> this emulation stopped working:
>
> ~/work/qemu/build/qemu-system-riscv64 \
> -machine virt -nographic -m 8G -smp 8 \
> -kernel ./uboot-ubuntu/usr/lib/u-boot/qemu-riscv64_smode/uboot.elf \
> -drive file=snapshot.img,format=qcow2,if=virtio \
> -netdev bridge,id=bridge1,br=virbr0 -device
> virtio-net-pci,netdev=bridge1
>
>
> This is basically a guest created via the official Canonical tutorial:
>
> https://wiki.ubuntu.com/RISC-V/QEMU
>
> The error being thrown:
>
> =================
>
> Boot HART ID : 4
> Boot HART Domain : root
> Boot HART Priv Version : v1.12
> Boot HART Base ISA : rv64imafdch
> Boot HART ISA Extensions : time,sstc
> Boot HART PMP Count : 16
> Boot HART PMP Granularity : 4
> Boot HART PMP Address Bits: 54
> Boot HART MHPM Count : 16
> Boot HART MIDELEG : 0x0000000000001666
> Boot HART MEDELEG : 0x0000000000f0b509
>
>
> U-Boot 2022.07+dfsg-1ubuntu4.2 (Nov 24 2022 - 18:47:41 +0000)
>
> CPU:
> rv64imafdch_zicbom_zicboz_zicsr_zifencei_zihintpause_zawrs_zfa_zca_zcd_zba_zbb_zbc_zbs_sstc_svadu
> Model: riscv-virtio,qemu
> DRAM: Unhandled exception: Store/AMO access fault
> EPC: 00000000802018b8 RA: 00000000802126a0 TVAL: 00000000ff733f90
>
> Code: b823 06b2 bc23 06b2 b023 08b2 b423 08b2 (b823 08b2)
>
>
> resetting ...
> System reset not supported on this platform
> ### ERROR ### Please RESET the board ###
> QEMU 8.0.90 monitor - type 'help' for more infor
> =================
Can you try again after setting CONFIG_NR_DRAM_BANKS=2 in
qemu-riscv64_smode_defconfig and qemu-riscv64_spl_defconfig ?
Regards,
Anup
>
>
> Based on the change made I can make an educated guess on what is going wrong.
> We have another board with a similar memory topology you're making here, the
> Microchip Polarfire (microchip_pfsoc.c). We were having some problems with
> this
> board while trying to consolidate the boot process between all boards in
> hw/riscv/boot.c because of its non-continuous RAM bank. The full story can be
> read in the commit message of 4b402886ac89 ("hw/riscv: change
> riscv_compute_fdt_addr()
> semantics") but the short version can be seen in riscv_compute_fdt_addr()
> from boot.c:
>
> - if ram_start is less than 3072MiB, the FDT will be put at the lowest
> value
> between 3072 MiB and the end of that RAM bank;
>
> - if ram_start is higher than 3072 MiB the FDT will be put at the end of the
> RAM bank.
>
> So, after this patch, since riscv_compute_fdt_addr() is being used with the
> now
> lower RAM bank, the fdt is being put in LOW_MEM - fdt_size for any setup that
> has
> more than 1Gb RAM, and this breaks assumptions made by uboot and Ubuntu and
> possibly
> others that are trying to retrieve the FDT from the gap that you created
> between
> low and hi mem in this patch.
>
> In fact, this same Ubuntu guest I mentioned above will boot if I put only 1
> Gb of RAM
> (-m 1Gb). If I try with -m 1.1Gb I reproduce this error. This can be a
> validation of
> the guess I'm making here: Ubuntu is trying to fetch stuff (probably the fdt)
> from
> the gap between the memory areas.
>
> This change on top of this patch doesn't work either:
>
> $ git diff
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index 8fbdc7220c..dfff48d849 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -1335,9 +1335,16 @@ static void virt_machine_done(Notifier *notifier, void
> *data)
> kernel_start_addr, true, NULL);
> }
>
> - fdt_load_addr = riscv_compute_fdt_addr(memmap[VIRT_DRAM].base,
> + if (machine->ram_size < memmap[VIRT_DRAM].size) {
> + fdt_load_addr = riscv_compute_fdt_addr(memmap[VIRT_DRAM].base,
> memmap[VIRT_DRAM].size,
> machine);
> + } else {
> + fdt_load_addr = riscv_compute_fdt_addr(memmap[VIRT_DRAM_HIGH].base,
> + memmap[VIRT_DRAM_HIGH].size,
> + machine);
> + }
> +
>
>
> This would put the fdt at the end of the HI RAM for guests with more than 1Gb
> of RAM.
> This change in fact makes the situation even worse, breaking setups that were
> working
> before with this patch.
>
> There's a chance that reducing the gap between the RAM banks can make Ubuntu
> work
> reliably again but now I'm a little cold feet with this change.
>
>
> I think we'll need some kernel/Opensbi folks to weight in here to see if
> there's a
> failsafe memory setup that won't break distros out there and allow your
> passthrough
> to work.
>
>
>
> Thanks,
>
> Daniel
>
> >
> > Signed-off-by: Andrei Warkentin <andrei.warken...@intel.com>
> > Signed-off-by: Fei Wu <fei2...@intel.com>
> > ---
> > hw/riscv/virt.c | 74 ++++++++++++++++++++++++++++++++++++-----
> > include/hw/riscv/virt.h | 1 +
> > 2 files changed, 66 insertions(+), 9 deletions(-)
> >
> > diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> > index d90286dc46..8fbdc7220c 100644
> > --- a/hw/riscv/virt.c
> > +++ b/hw/riscv/virt.c
> > @@ -75,7 +75,9 @@
> > #error "Can't accomodate all IMSIC groups in address space"
> > #endif
> >
> > -static const MemMapEntry virt_memmap[] = {
> > +#define LOW_MEM (1 * GiB)
> > +
> > +static MemMapEntry virt_memmap[] = {
> > [VIRT_DEBUG] = { 0x0, 0x100 },
> > [VIRT_MROM] = { 0x1000, 0xf000 },
> > [VIRT_TEST] = { 0x100000, 0x1000 },
> > @@ -96,6 +98,7 @@ static const MemMapEntry virt_memmap[] = {
> > [VIRT_PCIE_ECAM] = { 0x30000000, 0x10000000 },
> > [VIRT_PCIE_MMIO] = { 0x40000000, 0x40000000 },
> > [VIRT_DRAM] = { 0x80000000, 0x0 },
> > + [VIRT_DRAM_HIGH] = { 0x100000000, 0x0 },
> > };
> >
> > /* PCIe high mmio is fixed for RV32 */
> > @@ -295,15 +298,12 @@ static void create_fdt_socket_cpus(RISCVVirtState *s,
> > int socket,
> > }
> > }
> >
> > -static void create_fdt_socket_memory(RISCVVirtState *s,
> > - const MemMapEntry *memmap, int socket)
> > +static void create_fdt_socket_mem_range(RISCVVirtState *s, uint64_t addr,
> > + uint64_t size, int socket)
> > {
> > char *mem_name;
> > - uint64_t addr, size;
> > MachineState *ms = MACHINE(s);
> >
> > - addr = memmap[VIRT_DRAM].base + riscv_socket_mem_offset(ms, socket);
> > - size = riscv_socket_mem_size(ms, socket);
> > mem_name = g_strdup_printf("/memory@%lx", (long)addr);
> > qemu_fdt_add_subnode(ms->fdt, mem_name);
> > qemu_fdt_setprop_cells(ms->fdt, mem_name, "reg",
> > @@ -313,6 +313,34 @@ static void create_fdt_socket_memory(RISCVVirtState *s,
> > g_free(mem_name);
> > }
> >
> > +static void create_fdt_socket_memory(RISCVVirtState *s,
> > + const MemMapEntry *memmap, int socket)
> > +{
> > + uint64_t addr, size;
> > + MachineState *mc = MACHINE(s);
> > + uint64_t sock_offset = riscv_socket_mem_offset(mc, socket);
> > + uint64_t sock_size = riscv_socket_mem_size(mc, socket);
> > +
> > + if (sock_offset < memmap[VIRT_DRAM].size) {
> > + uint64_t low_mem_end = memmap[VIRT_DRAM].base +
> > memmap[VIRT_DRAM].size;
> > +
> > + addr = memmap[VIRT_DRAM].base + sock_offset;
> > + size = MIN(low_mem_end - addr, sock_size);
> > + create_fdt_socket_mem_range(s, addr, size, socket);
> > +
> > + size = sock_size - size;
> > + if (size > 0) {
> > + create_fdt_socket_mem_range(s, memmap[VIRT_DRAM_HIGH].base,
> > + size, socket);
> > + }
> > + } else {
> > + addr = memmap[VIRT_DRAM_HIGH].base +
> > + sock_offset - memmap[VIRT_DRAM].size;
> > +
> > + create_fdt_socket_mem_range(s, addr, sock_size, socket);
> > + }
> > +}
> > +
> > static void create_fdt_socket_clint(RISCVVirtState *s,
> > const MemMapEntry *memmap, int socket,
> > uint32_t *intc_phandles)
> > @@ -1334,10 +1362,12 @@ static void virt_machine_done(Notifier *notifier,
> > void *data)
> >
> > static void virt_machine_init(MachineState *machine)
> > {
> > - const MemMapEntry *memmap = virt_memmap;
> > + MemMapEntry *memmap = virt_memmap;
> > RISCVVirtState *s = RISCV_VIRT_MACHINE(machine);
> > MemoryRegion *system_memory = get_system_memory();
> > MemoryRegion *mask_rom = g_new(MemoryRegion, 1);
> > + MemoryRegion *ram_below_4g, *ram_above_4g;
> > + uint64_t ram_size_low, ram_size_high;
> > char *soc_name;
> > DeviceState *mmio_irqchip, *virtio_irqchip, *pcie_irqchip;
> > int i, base_hartid, hart_count;
> > @@ -1448,6 +1478,17 @@ static void virt_machine_init(MachineState *machine)
> > }
> > }
> >
> > + if (machine->ram_size > LOW_MEM) {
> > + ram_size_high = machine->ram_size - LOW_MEM;
> > + ram_size_low = LOW_MEM;
> > + } else {
> > + ram_size_high = 0;
> > + ram_size_low = machine->ram_size;
> > + }
> > +
> > + memmap[VIRT_DRAM].size = ram_size_low;
> > + memmap[VIRT_DRAM_HIGH].size = ram_size_high;
> > +
> > if (riscv_is_32bit(&s->soc[0])) {
> > #if HOST_LONG_BITS == 64
> > /* limit RAM size in a 32-bit system */
> > @@ -1460,7 +1501,8 @@ static void virt_machine_init(MachineState *machine)
> > virt_high_pcie_memmap.size = VIRT32_HIGH_PCIE_MMIO_SIZE;
> > } else {
> > virt_high_pcie_memmap.size = VIRT64_HIGH_PCIE_MMIO_SIZE;
> > - virt_high_pcie_memmap.base = memmap[VIRT_DRAM].base +
> > machine->ram_size;
> > + virt_high_pcie_memmap.base = memmap[VIRT_DRAM_HIGH].base +
> > + memmap[VIRT_DRAM_HIGH].size;
> > virt_high_pcie_memmap.base =
> > ROUND_UP(virt_high_pcie_memmap.base,
> > virt_high_pcie_memmap.size);
> > }
> > @@ -1468,8 +1510,22 @@ static void virt_machine_init(MachineState *machine)
> > s->memmap = virt_memmap;
> >
> > /* register system main memory (actual RAM) */
> > + ram_below_4g = g_malloc(sizeof(*ram_below_4g));
> > + memory_region_init_alias(ram_below_4g, NULL, "ram-below-4g",
> > machine->ram,
> > + 0, memmap[VIRT_DRAM].size);
> > memory_region_add_subregion(system_memory, memmap[VIRT_DRAM].base,
> > - machine->ram);
> > + ram_below_4g);
> > +
> > + if (memmap[VIRT_DRAM_HIGH].size) {
> > + ram_above_4g = g_malloc(sizeof(*ram_above_4g));
> > + memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g",
> > + machine->ram,
> > + memmap[VIRT_DRAM].size,
> > + memmap[VIRT_DRAM_HIGH].size);
> > + memory_region_add_subregion(system_memory,
> > + memmap[VIRT_DRAM_HIGH].base,
> > + ram_above_4g);
> > + }
> >
> > /* boot rom */
> > memory_region_init_rom(mask_rom, NULL, "riscv_virt_board.mrom",
> > diff --git a/include/hw/riscv/virt.h b/include/hw/riscv/virt.h
> > index e5c474b26e..36004eb6ef 100644
> > --- a/include/hw/riscv/virt.h
> > +++ b/include/hw/riscv/virt.h
> > @@ -79,6 +79,7 @@ enum {
> > VIRT_IMSIC_S,
> > VIRT_FLASH,
> > VIRT_DRAM,
> > + VIRT_DRAM_HIGH,
> > VIRT_PCIE_MMIO,
> > VIRT_PCIE_PIO,
> > VIRT_PLATFORM_BUS,
>
