builtin-run: Always use RAM size in bytes

The user can specify the virtual machine memory size in MB, which is saved
in cfg->ram_size. kvmtool validates it against the host memory size,
converted from bytes to MB. ram_size is then converted to bytes, and this
is how it is used throughout the rest of kvmtool.

To avoid any confusion about the unit of measurement, especially once the
user is allowed to specify the unit of measurement, always use ram_size in
bytes.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-and-Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220616134828.129006-3-alexandru.elisei@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

3 files changed, 15 insertions, 13 deletions

diff --git a/builtin-run.c b/builtin-run.c
index 0126c9fb..2bf93fe1 100644
--- a/builtin-run.c
+++ b/builtin-run.c
@@ -36,6 +36,7 @@
 
 #include <linux/types.h>
 #include <linux/err.h>
+#include <linux/sizes.h>
 
 #include <sys/utsname.h>
 #include <sys/types.h>
@@ -264,7 +265,7 @@ static u64 host_ram_size(void)
 		return 0;
 	}
 
-	return (nr_pages * page_size) >> MB_SHIFT;
+	return (u64)nr_pages * page_size;
 }
 
 /*
@@ -278,11 +279,11 @@ static u64 get_ram_size(int nr_cpus)
 	u64 available;
 	u64 ram_size;
 
-	ram_size	= 64 * (nr_cpus + 3);
+	ram_size	= (u64)SZ_64M * (nr_cpus + 3);
 
 	available	= host_ram_size() * RAM_SIZE_RATIO;
 	if (!available)
-		available = MIN_RAM_SIZE_MB;
+		available = MIN_RAM_SIZE;
 
 	if (ram_size > available)
 		ram_size	= available;
@@ -595,13 +596,13 @@ static struct kvm *kvm_cmd_run_init(int argc, const char **argv)
 
 	if (!kvm->cfg.ram_size)
 		kvm->cfg.ram_size = get_ram_size(kvm->cfg.nrcpus);
+	else
+		kvm->cfg.ram_size <<= MB_SHIFT;
 
 	if (kvm->cfg.ram_size > host_ram_size())
 		pr_warning("Guest memory size %lluMB exceeds host physical RAM size %lluMB",
-			(unsigned long long)kvm->cfg.ram_size,
-			(unsigned long long)host_ram_size());
-
-	kvm->cfg.ram_size <<= MB_SHIFT;
+			(unsigned long long)kvm->cfg.ram_size >> MB_SHIFT,
+			(unsigned long long)host_ram_size() >> MB_SHIFT);
 
 	if (!kvm->cfg.dev)
 		kvm->cfg.dev = DEFAULT_KVM_DEV;
@@ -676,12 +677,12 @@ static struct kvm *kvm_cmd_run_init(int argc, const char **argv)
 	if (kvm->cfg.kernel_filename) {
 		printf("  # %s run -k %s -m %Lu -c %d --name %s\n", KVM_BINARY_NAME,
 		       kvm->cfg.kernel_filename,
-		       (unsigned long long)kvm->cfg.ram_size / 1024 / 1024,
+		       (unsigned long long)kvm->cfg.ram_size >> MB_SHIFT,
 		       kvm->cfg.nrcpus, kvm->cfg.guest_name);
 	} else if (kvm->cfg.firmware_filename) {
 		printf("  # %s run --firmware %s -m %Lu -c %d --name %s\n", KVM_BINARY_NAME,
 		       kvm->cfg.firmware_filename,
-		       (unsigned long long)kvm->cfg.ram_size / 1024 / 1024,
+		       (unsigned long long)kvm->cfg.ram_size >> MB_SHIFT,
 		       kvm->cfg.nrcpus, kvm->cfg.guest_name);
 	}
 
diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h
index 6a5720c4..31bc8952 100644
--- a/include/kvm/kvm-config.h
+++ b/include/kvm/kvm-config.h
@@ -5,6 +5,8 @@
 #include "kvm/vfio.h"
 #include "kvm/kvm-config-arch.h"
 
+#include <linux/sizes.h>
+
 #define DEFAULT_KVM_DEV		"/dev/kvm"
 #define DEFAULT_CONSOLE		"serial"
 #define DEFAULT_NETWORK		"user"
@@ -15,14 +17,13 @@
 #define DEFAULT_SCRIPT		"none"
 #define DEFAULT_SANDBOX_FILENAME "guest/sandbox.sh"
 
-#define MIN_RAM_SIZE_MB		(64ULL)
-#define MIN_RAM_SIZE_BYTE	(MIN_RAM_SIZE_MB << MB_SHIFT)
+#define MIN_RAM_SIZE		SZ_64M
 
 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_size;
+	u64 ram_size;		/* Guest memory size, in bytes */
 	u8 num_net_devices;
 	u8 num_vfio_devices;
 	u64 vsock_cid;
diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h
index ad732e56..7b14b33b 100644
--- a/include/kvm/kvm.h
+++ b/include/kvm/kvm.h
@@ -87,7 +87,7 @@ struct kvm {
 	struct kvm_cpu		**cpus;
 
 	u32			mem_slots;	/* for KVM_SET_USER_MEMORY_REGION */
-	u64			ram_size;
+	u64			ram_size;	/* Guest memory size, in bytes */
 	void			*ram_start;
 	u64			ram_pagesize;
 	struct mutex		mem_banks_lock;