KVM: SVM: Add GHCB accessor functions for retrieving fields

Update the GHCB accessor functions to add functions for retrieve GHCB
fields by name. Update existing code to use the new accessor functions.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <664172c53a5fb4959914e1a45d88e805649af0ad.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/svm.h

@@ -379,6 +379,16 @@ struct vmcb {
 				(unsigned long *)&ghcb->save.valid_bitmap);	\
 	}									\
 										\
+	static inline u64 ghcb_get_##field(struct ghcb *ghcb)			\
+	{									\
+		return ghcb->save.field;					\
+	}									\
+										\
+	static inline u64 ghcb_get_##field##_if_valid(struct ghcb *ghcb)	\
+	{									\
+		return ghcb_##field##_is_valid(ghcb) ? ghcb->save.field : 0;	\
+	}									\
+										\
 	static inline void ghcb_set_##field(struct ghcb *ghcb, u64 value)	\
 	{									\
 		__set_bit(GHCB_BITMAP_IDX(field),				\

arch/x86/kernel/cpu/vmware.c

@@ -501,12 +501,12 @@ static bool vmware_sev_es_hcall_finish(struct ghcb *ghcb, struct pt_regs *regs)
 	      ghcb_rbp_is_valid(ghcb)))
 		return false;
 
-	regs->bx = ghcb->save.rbx;
-	regs->cx = ghcb->save.rcx;
-	regs->dx = ghcb->save.rdx;
-	regs->si = ghcb->save.rsi;
-	regs->di = ghcb->save.rdi;
-	regs->bp = ghcb->save.rbp;
+	regs->bx = ghcb_get_rbx(ghcb);
+	regs->cx = ghcb_get_rcx(ghcb);
+	regs->dx = ghcb_get_rdx(ghcb);
+	regs->si = ghcb_get_rsi(ghcb);
+	regs->di = ghcb_get_rdi(ghcb);
+	regs->bp = ghcb_get_rbp(ghcb);
 
 	return true;
 }