Re: [Qemu-devel] [PATCH v7 03/17] hw/arm/virt: Split the memory map description

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 21 Feb 2019 18:21:11 +0100
Auger Eric <eric.auger@redhat.com> wrote:

> Hi Igor,
> On 2/21/19 5:19 PM, Igor Mammedov wrote:
> > On Wed, 20 Feb 2019 23:39:49 +0100
> > Eric Auger <eric.auger@redhat.com> wrote:
> >   
> >> In the prospect to introduce an extended memory map supporting more
> >> RAM, let's split the memory map array into two parts:
> >>
> >> - the former a15memmap contains regions below and including the RAM  
> >   
> >> - extended_memmap, only initialized with entries located after the RAM.
> >>   Only the size of the region is initialized there since their base
> >>   address will be dynamically computed, depending on the top of the
> >>   RAM (initial RAM at the moment), with same alignment as their size.  
> > can't parse this part and pinpoint what is 'their', care to rephrase?  
> Only the size of the High IO region entries is initialized (there are
> currently 3 entries:  VIRT_HIGH_GIC_REDIST2, VIRT_HIGH_PCIE_ECAM,
> VIRT_HIGH_PCIE_MMIO). The base address is dynamically computed so it is
> not initialized.
> > 
> >   
> >> This new split will allow to grow the RAM size without changing the
> >> description of the high regions.
> >>
> >> The patch also moves the memory map setup  
> > s/moves/makes/
> > s/$/dynamic and moves it/
> >   
> >> into machvirt_init().  
> >   
> >> The rationale is the memory map will be soon affected by the  
> >   
> >> kvm_type() call that happens after virt_instance_init() and  
> > is dependency on kvm_type() still valid,
> > shouldn't split memmap work for TCG just fine as well?  
> See in 08/17: in TCG mode the memory map  will be "frozen" (set_memmap)
> in machvirt_init. Otherwise set_memmap is called from kvm_type().
> 
> Split memmap works both in TCG and in accelerated mode.
> 
> I will rephrase the commit message.
> >   
> >> before machvirt_init().
> >>
> >> The memory map is unchanged (the top of the initial RAM still is
> >> 256GiB). Then come the high IO regions with same layout as before.
> >>
> >> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> >> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> >>
> >> ---
> >> v6 -> v7:
> >> - s/a15memmap/base_memmap
> >> - slight rewording of the commit message
> >> - add "if there is less than 256GiB of RAM then the floating area
> >>   starts at the 256GiB mark" in the comment associated to the floating
> >>   memory map
> >> - Added Peter's R-b
> >>
> >> v5 -> v6
> >> - removal of many macros in units.h
> >> - introduce the virt_set_memmap helper
> >> - new computation for offsets of high IO regions
> >> - add comments
> >> ---
> >>  hw/arm/virt.c         | 48 +++++++++++++++++++++++++++++++++++++------
> >>  include/hw/arm/virt.h | 14 +++++++++----
> >>  2 files changed, 52 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> >> index a1955e7764..12039a0367 100644
> >> --- a/hw/arm/virt.c
> >> +++ b/hw/arm/virt.c
> >> @@ -29,6 +29,7 @@
> >>   */
> >>  
> >>  #include "qemu/osdep.h"
> >> +#include "qemu/units.h"
> >>  #include "qapi/error.h"
> >>  #include "hw/sysbus.h"
> >>  #include "hw/arm/arm.h"
> >> @@ -121,7 +122,7 @@
> >>   * Note that devices should generally be placed at multiples of 0x10000,
> >>   * to accommodate guests using 64K pages.
> >>   */
> >> -static const MemMapEntry a15memmap[] = {
> >> +static const MemMapEntry base_memmap[] = {
> >>      /* Space up to 0x8000000 is reserved for a boot ROM */
> >>      [VIRT_FLASH] =              {          0, 0x08000000 },
> >>      [VIRT_CPUPERIPHS] =         { 0x08000000, 0x00020000 },
> >> @@ -149,11 +150,21 @@ static const MemMapEntry a15memmap[] = {
> >>      [VIRT_PCIE_PIO] =           { 0x3eff0000, 0x00010000 },
> >>      [VIRT_PCIE_ECAM] =          { 0x3f000000, 0x01000000 },
> >>      [VIRT_MEM] =                { 0x40000000, RAMLIMIT_BYTES },
> >> +};
> >> +
> >> +/*
> >> + * Highmem IO Regions: This memory map is floating, located after the RAM.
> >> + * Each IO region offset will be dynamically computed, depending on the  
> > s/IO region offset/MemMapEntry base (GPA)/  
> >> + * top of the RAM, so that its base get the same alignment as the size,  
> >   
> >> + * ie. a 512GiB region will be aligned on a 512GiB boundary. If there is  
> > s/region/entry/
> >   
> >> + * less than 256GiB of RAM, the floating area starts at the 256GiB mark.
> >> + */
> >> +static MemMapEntry extended_memmap[] = {
> >>      /* Additional 64 MB redist region (can contain up to 512 redistributors) */
> >> -    [VIRT_HIGH_GIC_REDIST2] =   { 0x4000000000ULL, 0x4000000 },
> >> -    [VIRT_HIGH_PCIE_ECAM] =     { 0x4010000000ULL, 0x10000000 },
> >> -    /* Second PCIe window, 512GB wide at the 512GB boundary */
> >> -    [VIRT_HIGH_PCIE_MMIO] =     { 0x8000000000ULL, 0x8000000000ULL },
> >> +    [VIRT_HIGH_GIC_REDIST2] =   { 0x0, 64 * MiB },
> >> +    [VIRT_HIGH_PCIE_ECAM] =     { 0x0, 256 * MiB },
> >> +    /* Second PCIe window */
> >> +    [VIRT_HIGH_PCIE_MMIO] =     { 0x0, 512 * GiB },
> >>  };
> >>  
> >>  static const int a15irqmap[] = {
> >> @@ -1354,6 +1365,30 @@ static uint64_t virt_cpu_mp_affinity(VirtMachineState *vms, int idx)
> >>      return arm_cpu_mp_affinity(idx, clustersz);
> >>  }
> >>  
> >> +static void virt_set_memmap(VirtMachineState *vms)
> >> +{
> >> +    hwaddr base;
> >> +    int i;
> >> +
> >> +    vms->memmap = extended_memmap;  
> > I probably don't see something but ...
> >   
> >> +
> >> +    for (i = 0; i < ARRAY_SIZE(base_memmap); i++) {
> >> +        vms->memmap[i] = base_memmap[i];  
> > 
> > ARRAY_SIZE(base_memmap) > 3
> > ARRAY_SIZE(extended_memmap) == 3
> > as result shouldn't we observe OOB at vms->memmap[i] access
> > starting from i==3 ?  
> ARRAY_SIZE(extended_memmap) = ARRAY_SIZE(base_memmap) + 3
> VIRT_HIGH_GIC_REDIST2 =  VIRT_LOWMEMMAP_LAST is what you miss.
Yep, that's the trick.
It is too much subtle for my taste,
is it possible to make extended_memmap sizing more explicit/trivial,
so one could see it right away without figuring out how indexes influence array size?


> /* indices of IO regions located after the RAM */
> enum {
>     VIRT_HIGH_GIC_REDIST2 =  VIRT_LOWMEMMAP_LAST,
>     VIRT_HIGH_PCIE_ECAM,
>     VIRT_HIGH_PCIE_MMIO,
> };
> 
> >   
> >> +    }
> >> +
> >> +    vms->high_io_base = 256 * GiB; /* Top of the legacy initial RAM region */
> >> +    base = vms->high_io_base;
> >> +
> >> +    for (i = VIRT_LOWMEMMAP_LAST; i < ARRAY_SIZE(extended_memmap); i++) {  
> > not sure why VIRT_LOWMEMMAP_LAST is needed at all, one could just continue
> > with current 'i' value, provided extended_memmap wasn't corrupted by previous
> > loop.  
> Yep maybe. But I think it is less error prone like this if someone later
> on adds some intermediate manipulation on i.
> > And does this loop ever executes? VIRT_LOWMEMMAP_LAST > ARRAY_SIZE(extended_memmap)  
> yes it does
> 
> Thanks
> 
> Eric
> >   
> >> +        hwaddr size = extended_memmap[i].size;
> >> +
> >> +        base = ROUND_UP(base, size);
> >> +        vms->memmap[i].base = base;
> >> +        vms->memmap[i].size = size;
> >> +        base += size;
> >> +    }
> >> +}
> >> +
> >>  static void machvirt_init(MachineState *machine)
> >>  {
> >>      VirtMachineState *vms = VIRT_MACHINE(machine);
> >> @@ -1368,6 +1403,8 @@ static void machvirt_init(MachineState *machine)
> >>      bool firmware_loaded = bios_name || drive_get(IF_PFLASH, 0, 0);
> >>      bool aarch64 = true;
> >>  
> >> +    virt_set_memmap(vms);
> >> +
> >>      /* We can probe only here because during property set
> >>       * KVM is not available yet
> >>       */
> >> @@ -1843,7 +1880,6 @@ static void virt_instance_init(Object *obj)
> >>                                      "Valid values are none and smmuv3",
> >>                                      NULL);
> >>  
> >> -    vms->memmap = a15memmap;
> >>      vms->irqmap = a15irqmap;
> >>  }
> >>  
> >> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> >> index a27086d524..3dc7a6c5d5 100644
> >> --- a/include/hw/arm/virt.h
> >> +++ b/include/hw/arm/virt.h
> >> @@ -64,7 +64,6 @@ enum {
> >>      VIRT_GIC_VCPU,
> >>      VIRT_GIC_ITS,
> >>      VIRT_GIC_REDIST,
> >> -    VIRT_HIGH_GIC_REDIST2,
> >>      VIRT_SMMU,
> >>      VIRT_UART,
> >>      VIRT_MMIO,
> >> @@ -74,12 +73,18 @@ enum {
> >>      VIRT_PCIE_MMIO,
> >>      VIRT_PCIE_PIO,
> >>      VIRT_PCIE_ECAM,
> >> -    VIRT_HIGH_PCIE_ECAM,
> >>      VIRT_PLATFORM_BUS,
> >> -    VIRT_HIGH_PCIE_MMIO,
> >>      VIRT_GPIO,
> >>      VIRT_SECURE_UART,
> >>      VIRT_SECURE_MEM,
> >> +    VIRT_LOWMEMMAP_LAST,
> >> +};
> >> +
> >> +/* indices of IO regions located after the RAM */
> >> +enum {
> >> +    VIRT_HIGH_GIC_REDIST2 =  VIRT_LOWMEMMAP_LAST,
> >> +    VIRT_HIGH_PCIE_ECAM,
> >> +    VIRT_HIGH_PCIE_MMIO,
> >>  };
> >>  
> >>  typedef enum VirtIOMMUType {
> >> @@ -116,7 +121,7 @@ typedef struct {
> >>      int32_t gic_version;
> >>      VirtIOMMUType iommu;
> >>      struct arm_boot_info bootinfo;
> >> -    const MemMapEntry *memmap;
> >> +    MemMapEntry *memmap;
> >>      const int *irqmap;
> >>      int smp_cpus;
> >>      void *fdt;
> >> @@ -126,6 +131,7 @@ typedef struct {
> >>      uint32_t msi_phandle;
> >>      uint32_t iommu_phandle;
> >>      int psci_conduit;
> >> +    hwaddr high_io_base;
> >>  } VirtMachineState;
> >>  
> >>  #define VIRT_ECAM_ID(high) (high ? VIRT_HIGH_PCIE_ECAM : VIRT_PCIE_ECAM)  
> > 
> >