Re: [PATCH v2 kvmtool 12/12] arm64: Allow the user to specify the RAM base address

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Hi Andre,

Thank you for having a look!

On Fri, May 20, 2022 at 06:20:15PM +0100, Andre Przywara wrote:
> On Mon, 16 May 2022 16:55:26 +0100
> Alexandru Elisei <alexandru.elisei@xxxxxxx> wrote:
> 
> Hi,
> 
> > Allow the user to specify the RAM base address by using -m/--mem size@addr
> > command line argument. The base address must be above 2GB, as to not
> > overlap with the MMIO I/O region.
> 
> Just started to play with this, in general the series looks good to me on
> a first glance. I will review in anger next week.
> Meanwhile: when you start kvmtool without explicitly specifying a ram size
> on the command line, the code misses to initialise cfg.ram_addr, so it
> stays at 0 and kvmtool reports:
>   Fatal: RAM address is below 2GB
> One possible fix would be to initialise this in get_ram_size() to
> kvm__arch_default_ram_address(), I guess, but you might find a better solution.

This is indeed an issue. I usually specify the number of vcpus and the
memory size when I create a VM, and I overlooked what happens with the
default values. I will incorporate this scenario into my testing.

Will send an updated series with the bug fixed as soon as possible. In the
meantime, this fixed the issue for me and I plan to incorporate it into the
series after more testing:

diff --git a/builtin-run.c b/builtin-run.c
index 26e6e9974009..36a255bc14f9 100644
--- a/builtin-run.c
+++ b/builtin-run.c
@@ -137,7 +137,6 @@ static int mem_parser(const struct option *opt, const char *arg, int unset)
        if (kvm->cfg.ram_size == 0)
                die("Invalid RAM size: %s", arg);

-       kvm->cfg.ram_addr = kvm__arch_default_ram_address();
        if (kvm__arch_has_cfg_ram_address() && *next == '@') {
                next++;
                if (*next == '\0')
@@ -622,6 +621,7 @@ static struct kvm *kvm_cmd_run_init(int argc, const char **argv)

        nr_online_cpus = sysconf(_SC_NPROCESSORS_ONLN);
        kvm->cfg.custom_rootfs_name = "default";
+       kvm->cfg.ram_addr = kvm__arch_default_ram_address();

        while (argc != 0) {
                BUILD_OPTIONS(options, &kvm->cfg, kvm);

Thanks,
Alex

> 
> Cheers,
> Andre
> 
> > 
> > Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> > ---
> >  arm/aarch64/include/kvm/kvm-arch.h |  2 ++
> >  arm/aarch64/kvm.c                  |  5 ++++-
> >  arm/kvm.c                          |  7 +++++--
> >  builtin-run.c                      | 29 +++++++++++++++++++++++++----
> >  include/kvm/kvm-config.h           |  1 +
> >  include/kvm/kvm.h                  | 12 ++++++++++++
> >  6 files changed, 49 insertions(+), 7 deletions(-)
> > 
> > diff --git a/arm/aarch64/include/kvm/kvm-arch.h b/arm/aarch64/include/kvm/kvm-arch.h
> > index ff857ca6e7b4..02d09a413831 100644
> > --- a/arm/aarch64/include/kvm/kvm-arch.h
> > +++ b/arm/aarch64/include/kvm/kvm-arch.h
> > @@ -10,6 +10,8 @@ void kvm__arch_enable_mte(struct kvm *kvm);
> >  
> >  #define MAX_PAGE_SIZE	SZ_64K
> >  
> > +#define ARCH_HAS_CFG_RAM_ADDRESS	1
> > +
> >  #include "arm-common/kvm-arch.h"
> >  
> >  #endif /* KVM__KVM_ARCH_H */
> > diff --git a/arm/aarch64/kvm.c b/arm/aarch64/kvm.c
> > index af8e7eae0da2..14ffae9e39dc 100644
> > --- a/arm/aarch64/kvm.c
> > +++ b/arm/aarch64/kvm.c
> > @@ -44,6 +44,9 @@ void kvm__arch_validate_cfg(struct kvm *kvm)
> >  		die("RAM size 0x%llx exceeds maximum allowed 0x%llx",
> >  		    kvm->cfg.ram_size, ARM_LOMAP_MAX_MEMORY);
> >  	}
> > +
> > +	if (kvm->cfg.ram_addr < ARM_MEMORY_AREA)
> > +		die("RAM address is below %luGB", ARM_MEMORY_AREA >> 30);
> >  }
> >  
> >  u64 kvm__arch_default_ram_address(void)
> > @@ -117,7 +120,7 @@ int kvm__get_vm_type(struct kvm *kvm)
> >  		return 0;
> >  
> >  	/* Otherwise, compute the minimal required IPA size */
> > -	max_ipa = ARM_MEMORY_AREA + kvm->cfg.ram_size - 1;
> > +	max_ipa = kvm->cfg.ram_addr + kvm->cfg.ram_size - 1;
> >  	ipa_bits = max(32, fls_long(max_ipa));
> >  	pr_debug("max_ipa %lx ipa_bits %d max_ipa_bits %d",
> >  		 max_ipa, ipa_bits, max_ipa_bits);
> > diff --git a/arm/kvm.c b/arm/kvm.c
> > index abcccfabf59e..d51cc15d8b1c 100644
> > --- a/arm/kvm.c
> > +++ b/arm/kvm.c
> > @@ -55,7 +55,7 @@ void kvm__init_ram(struct kvm *kvm)
> >  	madvise(kvm->arch.ram_alloc_start, kvm->arch.ram_alloc_size,
> >  		MADV_HUGEPAGE);
> >  
> > -	phys_start	= ARM_MEMORY_AREA;
> > +	phys_start	= kvm->cfg.ram_addr;
> >  	phys_size	= kvm->ram_size;
> >  	host_mem	= kvm->ram_start;
> >  
> > @@ -65,6 +65,9 @@ void kvm__init_ram(struct kvm *kvm)
> >  		    "address 0x%llx [err %d]", phys_size, phys_start, err);
> >  
> >  	kvm->arch.memory_guest_start = phys_start;
> > +
> > +	pr_debug("RAM created at 0x%llx - 0x%llx",
> > +		 phys_start, phys_start + phys_size - 1);
> >  }
> >  
> >  void kvm__arch_delete_ram(struct kvm *kvm)
> > @@ -201,7 +204,7 @@ bool kvm__load_firmware(struct kvm *kvm, const char *firmware_filename)
> >  
> >  	/* For default firmware address, lets load it at the begining of RAM */
> >  	if (fw_addr == 0)
> > -		fw_addr = ARM_MEMORY_AREA;
> > +		fw_addr = kvm->arch.memory_guest_start;
> >  
> >  	if (!validate_fw_addr(kvm, fw_addr))
> >  		die("Bad firmware destination: 0x%016llx", fw_addr);
> > diff --git a/builtin-run.c b/builtin-run.c
> > index 57c58be55159..26e6e9974009 100644
> > --- a/builtin-run.c
> > +++ b/builtin-run.c
> > @@ -131,12 +131,22 @@ static u64 parse_mem_option(const char *nptr, char **next)
> >  static int mem_parser(const struct option *opt, const char *arg, int unset)
> >  {
> >  	struct kvm *kvm = opt->ptr;
> > -	char *next;
> > +	char *next, *nptr;
> >  
> >  	kvm->cfg.ram_size = parse_mem_option(arg, &next);
> >  	if (kvm->cfg.ram_size == 0)
> >  		die("Invalid RAM size: %s", arg);
> >  
> > +	kvm->cfg.ram_addr = kvm__arch_default_ram_address();
> > +	if (kvm__arch_has_cfg_ram_address() && *next == '@') {
> > +		next++;
> > +		if (*next == '\0')
> > +			die("Missing memory address: %s", arg);
> > +
> > +		nptr = next;
> > +		kvm->cfg.ram_addr = parse_mem_option(nptr, &next);
> > +	}
> > +
> >  	if (*next != '\0')
> >  		die("Invalid memory specifier: %s", arg);
> >  
> > @@ -147,15 +157,26 @@ static int mem_parser(const struct option *opt, const char *arg, int unset)
> >  #define OPT_ARCH_RUN(...)
> >  #endif
> >  
> > +#ifdef ARCH_HAS_CFG_RAM_ADDRESS
> > +#define MEM_OPT_HELP_SHORT	"size[BKMGTP][@addr[BKMGTP]]"
> > +#define MEM_OPT_HELP_LONG						\
> > +	"Virtual machine memory size and optional base address, both"	\
> > +	" measured by default in megabytes (M)"
> > +#else
> > +#define MEM_OPT_HELP_SHORT	"size[BKMGTP]"
> > +#define MEM_OPT_HELP_LONG						\
> > +	"Virtual machine memory size, by default measured in"		\
> > +	" in megabytes (M)"
> > +#endif
> > +
> >  #define BUILD_OPTIONS(name, cfg, kvm)					\
> >  	struct option name[] = {					\
> >  	OPT_GROUP("Basic options:"),					\
> >  	OPT_STRING('\0', "name", &(cfg)->guest_name, "guest name",	\
> >  			"A name for the guest"),			\
> >  	OPT_INTEGER('c', "cpus", &(cfg)->nrcpus, "Number of CPUs"),	\
> > -	OPT_CALLBACK('m', "mem", NULL, "size[BKMGTP]",			\
> > -		     "Virtual machine memory size, by default measured"	\
> > -		     " in megabytes (M)", mem_parser, kvm),		\
> > +	OPT_CALLBACK('m', "mem", NULL, MEM_OPT_HELP_SHORT,		\
> > +		     MEM_OPT_HELP_LONG, mem_parser, kvm),		\
> >  	OPT_CALLBACK('d', "disk", kvm, "image or rootfs_dir", "Disk "	\
> >  			" image or rootfs directory", img_name_parser,	\
> >  			kvm),						\
> > diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h
> > index 31bc89520d52..45fe1caaebce 100644
> > --- a/include/kvm/kvm-config.h
> > +++ b/include/kvm/kvm-config.h
> > @@ -23,6 +23,7 @@ struct kvm_config {
> >  	struct kvm_config_arch arch;
> >  	struct disk_image_params disk_image[MAX_DISK_IMAGES];
> >  	struct vfio_device_params *vfio_devices;
> > +	u64 ram_addr;		/* Guest memory physical base address, in bytes */
> >  	u64 ram_size;		/* Guest memory size, in bytes */
> >  	u8 num_net_devices;
> >  	u8 num_vfio_devices;
> > diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h
> > index 360430b78b1e..eb23e2f77310 100644
> > --- a/include/kvm/kvm.h
> > +++ b/include/kvm/kvm.h
> > @@ -197,6 +197,18 @@ int kvm__arch_free_firmware(struct kvm *kvm);
> >  bool kvm__arch_cpu_supports_vm(void);
> >  void kvm__arch_read_term(struct kvm *kvm);
> >  
> > +#ifdef ARCH_HAS_CFG_RAM_ADDRESS
> > +static inline bool kvm__arch_has_cfg_ram_address(void)
> > +{
> > +	return true;
> > +}
> > +#else
> > +static inline bool kvm__arch_has_cfg_ram_address(void)
> > +{
> > +	return false;
> > +}
> > +#endif
> > +
> >  void *guest_flat_to_host(struct kvm *kvm, u64 offset);
> >  u64 host_to_guest_flat(struct kvm *kvm, void *ptr);
> >  
> 
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