kvm tools: teach guest_flat_to_host about memory banks starting above 0

Running a guest with multiple banks of memory based above 0 causes the
guest_flat_to_host address conversion to fail, as it is assumed that
guest memory addresses are offset linearly from 0.

This patch changes the translation function so that the kvm_mem_bank
structures registered by kvm__register_mem are used to translate guest
addresses, rather than use an offset from the start of host memory.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

include/kvm/kvm.h

@@ -105,6 +105,8 @@ int kvm__arch_free_firmware(struct kvm *kvm);
 bool kvm__arch_cpu_supports_vm(void);
 void kvm__arch_periodic_poll(struct kvm *kvm);
 
+void *guest_flat_to_host(struct kvm *kvm, u64 offset);
+
 int load_flat_binary(struct kvm *kvm, int fd_kernel, int fd_initrd, const char *kernel_cmdline);
 bool load_bzimage(struct kvm *kvm, int fd_kernel, int fd_initrd, const char *kernel_cmdline, u16 vidmode);
 
@@ -120,11 +122,6 @@ static inline bool host_ptr_in_ram(struct kvm *kvm, void *p)
 	return kvm->ram_start <= p && p < (kvm->ram_start + kvm->ram_size);
 }
 
-static inline void *guest_flat_to_host(struct kvm *kvm, unsigned long offset)
-{
-	return kvm->ram_start + offset;
-}
-
 bool kvm__supports_extension(struct kvm *kvm, unsigned int extension);
 
 static inline void kvm__set_thread_name(const char *name)

kvm.c

@@ -184,6 +184,23 @@ int kvm__register_mem(struct kvm *kvm, u64 guest_phys, u64 size, void *userspace
 	return 0;
 }
 
+void *guest_flat_to_host(struct kvm *kvm, u64 offset)
+{
+	struct kvm_mem_bank *bank;
+
+	list_for_each_entry(bank, &kvm->mem_banks, list) {
+		u64 bank_start = bank->guest_phys_addr;
+		u64 bank_end = bank_start + bank->size;
+
+		if (offset >= bank_start && offset < bank_end)
+			return bank->host_addr + (offset - bank_start);
+	}
+
+	pr_warning("unable to translate guest address 0x%llx to host",
+			(unsigned long long)offset);
+	return NULL;
+}
+
 int kvm__recommended_cpus(struct kvm *kvm)
 {
 	int ret;

x86/include/kvm/kvm-arch.h

@@ -33,13 +33,4 @@ struct kvm_arch {
 	struct interrupt_table	interrupt_table;
 };
 
-static inline void *guest_flat_to_host(struct kvm *kvm, unsigned long offset); /* In kvm.h */
-
-static inline void *guest_real_to_host(struct kvm *kvm, u16 selector, u16 offset)
-{
-	unsigned long flat = segment_to_flat(selector, offset);
-
-	return guest_flat_to_host(kvm, flat);
-}
-
 #endif /* KVM__KVM_ARCH_H */

x86/kvm.c

@@ -199,6 +199,13 @@ void kvm__irq_trigger(struct kvm *kvm, int irq)
 #define BOOT_PROTOCOL_REQUIRED	0x206
 #define LOAD_HIGH		0x01
 
+static inline void *guest_real_to_host(struct kvm *kvm, u16 selector, u16 offset)
+{
+	unsigned long flat = segment_to_flat(selector, offset);
+
+	return guest_flat_to_host(kvm, flat);
+}
+
 int load_flat_binary(struct kvm *kvm, int fd_kernel, int fd_initrd, const char *kernel_cmdline)
 {
 	void *p;